Clamp sensor and measuring device

The present invention relates to a clamp sensor that detects a detected value for a clamped object in a state where the clamped object has been clamped by a pair of clamp arms that are substantially arc-shaped in plan view, and to a measuring device that is equipped with the clamp sensor and measures a measured value for the clamped object.

As an example of this type of clamp sensor, the clamp sensor disclosed by the present applicant in Patent Literature 1 indicated below is known. This clamp sensor includes a movable sensor and a fixed sensor that are formed so as to be substantially arc-shaped in plan view. The movable sensor has a connecting pin inserted through a base end thereof to connect the movable sensor so as to be rotatable about the base end. When using this clamp sensor to detect a current flowing through an electric wire for example, a lever provided at the base end of the movable sensor is held. At this time, the movable sensor rotates so that the front ends of the sensors become separated. After this, the electric wire is passed through the separated front ends, and the holding of the lever is then released. Here, due to the biasing force of a spring, the front ends of the sensors are placed in contact with each other, so that the electric wire becomes surrounded and clamped by a ring-shaped body constructed by the sensors. The current flowing through the electric wire is then detected by the sensors.

Non Patent Literature

Patent Literature 1

Japanese Laid-open Patent Publication No. 2007-17188 (see pages 4-5, FIG. 1)

Problem to be Solved by the Invention

However, the clamp sensor described above has the following problem to be solved. That is, with this type of clamp sensor including the clamp sensor described above, to achieve sufficient sensitivity, the sensors have to be formed with a relatively high thickness and are substantially square in cross section. This means that when using the clamp sensor described above, there is the problem to be solved that when other electric wires are disposed in the vicinity of the electric wire to be measured, or when there is an obstacle in the vicinity of the electric wire to be measured, it is difficult to insert the front ends of the sensors into the gaps between the wire to be measured and the other wires or obstacle, which prevents the wire to be measured from being clamped with the sensors.

The present invention was conceived in view of the above problem to be solved and has a principal object of providing a clamp sensor and a measuring device capable of reliably clamping a clamped object.

Solution to Problem

To achieve the stated object, the clamp sensor according to an aspect of this application comprises: a pair of clamp arms that are formed so as to be substantially arc-shaped in plan view, that are configured so that at least one of the clamp arms is rotatable so that respective front ends of the clamp arms open and close, and that form a ring-shaped body in a state where the front ends are closed, wherein the clamp sensor is capable of detecting a detected value of a clamped object in a state where the clamped object is clamped by the clamp arms, front end portions of the clamp arms have a pair of first facing surfaces that construct an outer circumferential surface and an inner circumferential surface of the ring-shaped body, a pair of second facing surfaces that construct two side surfaces of the ring-shaped body, and a plurality of pairs of third facing surfaces that are inclined with respect to the first facing surfaces and the second facing surfaces, and the front end portions of the clamp arms are formed so that out of edges that construct an outer form of a section perpendicular to a length direction of each clamp arm, a length of a segment that joins both ends of at least one edge out of the edges that correspond to the third facing surfaces is longer than a shortest length out of lengths of the edges that respectively correspond to the first facing surfaces and the second facing surfaces.

Also, with the clamp sensor according to an aspect of this application, the front end portions of the clamp arms are formed so that lengths of all segments that join both ends of the edges that correspond to the third facing surfaces are longer than the shortest length out of lengths of the edges that respectively correspond to the first facing surfaces and the second facing surfaces.

Also, the clamp sensor according to an aspect of this application comprises: a pair of clamp arms that are formed so as to be substantially arc-shaped in plan view, that are configured so that at least one of the clamp arms is rotatable so that respective front ends of the clamp arms open and close, and that form a ring-shaped body in a state where the front ends are closed, wherein the clamp sensor is capable of detecting a detected value of a clamped object in a state where the clamped object is clamped by the clamp arms, front end portions of the clamp arms have a pair of first facing surfaces that construct an outer circumferential surface and an inner circumferential surface of the ring-shaped body, a pair of second facing surfaces that construct two side surfaces of the ring-shaped body, and a plurality of pairs of third facing surfaces that are inclined with respect to the first facing surfaces and the second facing surfaces, and the front end portions of the clamp arms are formed so that out of edges that construct an outer form of a section perpendicular to a length direction of each clamp arm, an opposing distance between a segment that joins both ends of one edge out of a pair of facing edges that correspond to the third facing surfaces and a segment that joins both ends of another edge in the pair is within a range of over ( 100 /√2)% but no greater than 110% of a shorter distance out of an opposing distance between edges corresponding to the first facing surfaces and an opposing distance between edges corresponding to the second facing surfaces out of the edges.

Also, with the clamp sensor according to an aspect of this application, the front end portions of the clamp arms are formed so that the opposing distance between all combinations of the facing edges is within a range of over ( 100 /√2)% but no greater than 110% of the shorter distance out of the opposing distance between edges corresponding to the first facing surfaces and the opposing distance between edges corresponding to the second facing surfaces.

Also, with the clamp sensor according to an aspect of this application comprises: a pair of clamp arms that are formed so as to be substantially arc-shaped in plan view, that are configured so that at least one of the clamp arms is rotatable so that respective front ends of the clamp arms open and close, and that form a ring-shaped body in a state where the front ends are closed, wherein the clamp sensor is capable of detecting a detected value of a clamped object in a state where the clamped object is clamped by the clamp arms, front end portions of the clamp arms have a pair of first facing surfaces that construct an outer circumferential surface and an inner circumferential surface of the ring-shaped body, a pair of second facing surfaces that construct two side surfaces of the ring-shaped body, and a plurality of pairs of third facing surfaces that are inclined with respect to the first facing surfaces and the second facing surfaces, and the front end portions of the clamp arms are formed so that out of edges that construct an outer form of a section perpendicular to a length direction of each clamp arm, a length of a segment that joins both ends of at least one edge out of the edges that correspond to the third facing surfaces is within a range of at least 57% but less than 1000% of a shortest length out of lengths of the edges that respectively correspond to the first facing surfaces and the second facing surfaces.

Also, with the clamp sensor according to an aspect of this application, the front end portions of the clamp arms are formed so that lengths of all segments that join both ends of edges out of the edges that correspond to the third facing surfaces are within a range of at least 57% but less than 1000% of a shortest length out of lengths of the edges that respectively correspond to the first facing surfaces and the second facing surfaces.

Also, the clamp sensor according to an aspect of this application comprises: a pair of clamp arms that are formed so as to be substantially arc-shaped in plan view, that are configured so that at least one of the clamp arms is rotatable so that respective front ends of the clamp arms open and close, and that form a ring-shaped body in a state where the front ends are closed, wherein the clamp sensor is capable of detecting a detected value of a clamped object in a state where the clamped object is clamped by the clamp arms, front end portions of the clamp arms have a pair of first facing surfaces that construct an outer circumferential surface and an inner circumferential surface of the ring-shaped body and a pair of second facing surfaces that construct two side surfaces of the ring-shaped body, and out of edges that construct an outer form of a section perpendicular to a length direction of each clamp arm, edges corresponding to the first facing surfaces are straight and edges corresponding to the second facing surfaces are arc-shaped so as to be outwardly curved.

Also, with the clamp sensor according to an aspect of this application, the front end portions of the clamp arms are formed so that a longest opposing distance between edges corresponding to the second facing surfaces along a direction perpendicular to a plane of an opening in the ring-shaped body is no greater than an opposing distance between edges corresponding to the first opposing distance.

Also, the clamp sensor according to an aspect of this application comprises: a pair of clamp arms that are formed so as to be substantially arc-shaped in plan view, that are configured so that at least one of the clamp arms is rotatable so that respective front ends of the clamp arms open and close, and that form a ring-shaped body in a state where the front ends are closed, wherein the clamp sensor is capable of detecting a detected value of a clamped object in a state where the clamped object is clamped by the clamp arms, front end portions of the clamp arms have a pair of first facing surfaces that construct an outer circumferential surface and an inner circumferential surface of the ring-shaped body, a pair of second facing surfaces that construct two side surfaces of the ring-shaped body, and two pairs of fourth facing surfaces that are positioned between the first facing surfaces and the second facing surfaces, and the front end portions of the clamp arms are formed so that out of edges that construct an outer form of a section perpendicular to a length direction of each clamp arm, edges corresponding to the first facing surfaces and edges corresponding to the second facing surfaces are straight and edges corresponding to the fourth facing surfaces are arc-shaped so as to be outwardly curved.

Also, with the clamp sensor according to an aspect of this application, the front end portions of the clamp arms are formed so that an opposing distance between the edges corresponding to the second facing surfaces is no greater than an opposing distance between the edges corresponding to the first facing surfaces.

Also, with the clamp sensor according to an aspect of this application, the clamp arms each have a sensor case that constructs an outer shell of the clamp arms, and each sensor case is formed so that a thickness of a part corresponding to a front end of each clamp arm is uniform or substantially uniform when looking from the section.

Also, with the clamp sensor according to an aspect of this application, the clamp arms are formed so that an area of the section at base end portions of the clamp arms is larger than an area of the section at the front end portions.

Also, with the clamp sensor according to an aspect of this application, the clamp arms each include a core in which a magnetic field is produced by a current flowing in the clamped object, a plane that passes any point, which is on a straight line that passes a top end of the ring-shaped body corresponding to the front ends and a centroid in plan view of a ring-shaped magnetic circuit formed by the cores when the ring-shaped body is formed and which is in a range that has a length equivalent to 40% of a straight line distance from the top end to the centroid and is centered on the centroid, and is perpendicular to the straight line is set as a boundary plane, and the clamp arms are formed so that an area of an outer form of the section at parts, as the front end portions, between the boundary plane and the front ends is smaller than an area of an outer form of the section at parts, as the base end portions, between the boundary plane and the base ends.

Also, with the clamp sensor according to an aspect of this application, a plane that passes any point, which is on a straight line that passes a top end of the ring-shaped body corresponding to the front ends and a centroid in plan view of an inner circumference of the ring-shaped body and which is in a range that has a length equivalent to 40% of a straight line distance from the top end to the centroid and is centered on the centroid, and is perpendicular to the straight line is set as a boundary plane, and the clamp arms are formed so that an area of an outer form of the section at parts, as the front end portions, between the boundary plane and the front ends is smaller than an area of an outer form of the section at parts, as the base end portions, between the boundary plane and the base ends.

Also, with the clamp sensor according to an aspect of this application, the clamp arms are formed so that the first facing surfaces that construct the outer circumferential surface at the front ends of the clamp arms produce a single flat surface that is perpendicular to a direction that connects a front end and a base end of the ring-shaped body in a state where the ring-shaped body is formed, and an opposing distance between the first facing surfaces at the front ends is shorter than an opposing distance between the first facing surfaces at other parts of the clamp arms aside from the front ends.

Also, with the clamp sensor according to an aspect of this application, the clamp arms are formed so that a length along the straight line between the outer circumferential surface of the ring-shaped body and a position that is 15 mm from a center of the top end along a direction that is perpendicular to the straight line and parallel to a plane of an opening in the ring-shaped body is within a range of at least 9 mm but no greater than 11 mm.

Also, with the clamp sensor according to an aspect of this application, the clamp arms are formed so that a longest distance out of straight line distances between any two points on the outer form of the section in a part between the boundary plane and the front ends is within a range of at least 1/6 but no greater than 1/5 of a separation distance between the front ends of the clamp arms in a state where the front ends are separated by a maximum amount.

Also, the measuring device according to an aspect of this application comprises: the clamp sensor according to an aspect of this application; and a measurer that measures a measured value for the clamped object based on the detected value detected by the clamp sensor.

Advantageous Effects of Invention

According to the clamp sensor according to an aspect of this application claim 1 and the measuring device according to an aspect of this application, the front end portions of the clamp arms are formed so that out of the edges constructing the outer form of the section, the length of a segment that joins both ends of at least one edge corresponding to a third facing surface is longer than a shortest length out of the lengths of the edges respectively corresponding to the first facing surfaces and the second facing surfaces. This means that in this clamp sensor and measuring device, the opposing distance between the edges that correspond to the third facing surfaces can be made shorter than the opposing distance between the edges corresponding to the first facing surfaces and the opposing distance between the edges corresponding to the second facing surfaces. As a result, according to this clamp sensor and measuring device, compared to the conventional configuration in which the outer form of the section at each front end portion of the clamp arms is rectangular and the diagonal distance of the section is longer than the opposing distance between the edges that correspond to the first facing surfaces and the opposing distance between the edges that correspond to the second facing surfaces (that is, a configuration where the corners of a rectangular pillar are not chamfered), it is possible to easily insert the front ends of the clamp arms into narrow gaps in a state where the measuring device is tilted. Accordingly, with this clamp sensor and the measuring device, the conductor that is the clamped object can be reliably clamped, even when another conductor or an obstacle is present in the vicinity of the conductor that is the clamped object.

Also, with the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, by forming the front end portions of the clamp arms so that the length of all of the segments that join both ends of edges corresponding to the third facing surfaces is longer than the length of the shortest length out of the lengths of the edges respectively corresponding to the first facing surfaces and the second facing surfaces, it is possible to make both of the opposing distances between edges that correspond to opposing distances between edges that correspond to the third facing surfaces shorter than the opposing distance between the edges that correspond to the first facing surfaces and the opposing distance between the edges that correspond to the second facing surfaces. This means that even when the measuring device is tilted so as to rotate in either of the clockwise or counterclockwise directions with the length direction of the measuring device as the rotational axis for example, it is possible to easily insert the front ends of the clamp arms into narrow gaps.

Also, according to the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, the front end portions of the clamp arms are formed so that out of the edges that construct the outer form of the section, the opposing distance between a segment that joins both ends of one edge out of edges corresponding to third facing surfaces and a segment that joins both ends of the other edge is within a range of over ( 100 /√2)% but no greater than 110% of a shorter distance out of the opposing distance between the edges corresponding to the first facing surfaces and the opposing distance between the edges corresponding to the second facing surfaces out of the edges. This means that with this clamp sensor and the measuring device, the opposing distance corresponding to the third facing surfaces can be made sufficiently shorter than the diagonal distance of a section in a conventional configuration formed so that the outer form of the section at the front end portions of the clamp arms is rectangular (a configuration where the corners of a rectangular pillar are not chamfered). As a result, with this clamp sensor and the measuring device, compared to the conventional configuration, the front ends of the clamp arms can be easily inserted into narrow gaps in a state where the measuring device is tilted. Accordingly, with this clamp sensor and the measuring device, the conductor that is the clamped object can be reliably clamped, even when for example another conductor or an obstacle is present in the vicinity of the conductor that is the clamped object.

Also, according to the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, by forming the front end portions of the clamp arms so that the opposing distance for every combination of the facing edges is within a range of over ( 100 /√2)% but no greater than 110% of the shorter distance out of the opposing distance between the edges corresponding to the first facing surfaces and the opposing distance between the edges corresponding to the second facing surfaces, it is possible to make all of the opposing distances corresponding to the third facing surfaces sufficiently shorter than the diagonal distance of the section in the conventional configuration. This means that with this clamp sensor and the measuring device, the front ends of the clamp arms can be easily inserted into narrow gaps, even in a state where for example the measuring device is tilted so as to rotate in either the clockwise or counterclockwise direction with the length direction of the measuring device as the rotational axis.

Also, according to the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, out of the edges that construct the outer form of the section, the length of a segment that joins both ends of at least one edge corresponding to the third facing surfaces is within a range of at least 57% but less than 1000% of a shortest length out of the lengths of the edges respectively corresponding to the first facing surfaces and the second facing surfaces. This means that according to this clamp sensor and the measuring device, it is possible to make the opposing distance between the edges corresponding to third facing surfaces sufficiently shorter than the diagonal distance of the section in the conventional configuration where the outer form of a section at front end portions of the clamp arms is rectangular (a configuration where corners of a rectangular pillar are not chamfered). As a result, according to this clamp sensor and the measuring device, compared to the conventional configuration, it is possible to easily insert the front ends of the clamp arms into narrow gaps in a state where the measuring device is tilted. Accordingly, with this clamp sensor and the measuring device, even if another conductor or an obstacle is present in the vicinity of the conductor that is the clamped object, it is still possible to reliably clamp the conductor that is the clamped object.

Also, according to the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, by forming the front end portions of the clamp arms so that lengths of all segments that join both ends of edges out of the edges corresponding to the third facing surfaces are within a range of at least 57% but less than 1000% of a shortest length out of the lengths of the edges respectively corresponding to the first facing surfaces and the second facing surfaces, it is possible to make all of the opposing distances between the edges corresponding to the third facing surfaces sufficiently shorter than the diagonal distance of the section in the conventional configuration. This means that according to this clamp sensor and the measuring device, the front ends of the clamp arms can be easily inserted into narrow gaps, even in a state where for example the measuring device is tilted so as to rotate in either the clockwise or counterclockwise direction with the length direction of the measuring device as the rotational axis.

Also, according to the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, by forming the front end portions of the clamp arms so that out of the edges that construct the outer form of the section, the edges corresponding to the first facing surfaces are straight and the edges corresponding to the second facing surfaces are arc-shaped so as to be outwardly curved, it is possible to make the longest opposing distance between edges corresponding to the second facing surfaces no greater than the opposing distance between edges corresponding to the first facing surfaces. This means that compared to the conventional configuration in which the outer form of the section at each front end portion of the clamp arms is rectangular and the diagonal distance of the section is longer than the opposing distance between the edges that correspond to the first facing surfaces and a longest opposing distance between the edges that correspond to the second facing surfaces (that is, a configuration where the corners of a rectangular pillar are not chamfered), it is possible to easily insert the front ends of the clamp arms into narrow gaps in a state where the measuring device is tilted. Accordingly, with this clamp sensor and the measuring device, even if another conductor or an obstacle is present in the vicinity of the conductor that is the clamped object, it is still possible to reliably clamp the conductor that is the clamped object.

Also, according to the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, the front end portions of the clamp arms are formed so that the longest opposing distance between edges corresponding to the second facing surfaces along a direction perpendicular to a plane of an opening in the ring-shaped body is no greater than an opposing distance between edges corresponding to the first facing surfaces. Accordingly, with this clamp sensor and the measuring device, by tilting the measuring device so as to reduce the angle of inclination of the plane of the opening in the ring-shaped body relative to the direction in which the conductor that is the clamped object extends, it is possible to insert the front ends of the clamp arms into narrow gaps even more easily.

Also, according to the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, by forming the front end portions of the clamp arms so that out of the edges that construct the outer form of the section, the edges corresponding to the first facing surfaces and the edges corresponding to the second facing surfaces are straight and the edges corresponding to the fourth facing surfaces are arc-shaped so as to be outwardly curved, it is possible to make the longest opposing distance between the edges corresponding to the fourth facing surfaces no greater than the opposing distance between the edges corresponding to the first facing surfaces. This means that compared to a conventional configuration (a configuration where the corners of a rectangular pillar are not chamfered) where the outer form of the section at each front end portion of the clamp arms is rectangular and the diagonal distance of the section is formed so as to be longer than the opposing distance between the edges corresponding to the first facing surfaces and the opposing distance between the edges corresponding to the second facing surfaces, it is possible to easily insert the front ends of the clamp arms into narrow gaps in a state where the measuring device is tilted. This means that according to the clamp sensor and the measuring device, even when another conductor or an obstacle is present in the vicinity of the conductor that is the clamped object, it is possible to reliably clamp the conductor that is the clamped object.

Also, according to the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, the front end portions of the clamp arms are formed so that the opposing distance between the edges corresponding to the second facing surfaces is no greater than the opposing distance between the edges corresponding to the first facing surfaces. This means that according to the clamp sensor and the measuring device, by tilting the measuring device so as to reduce the angle of inclination of the plane of the opening in the ring-shaped body relative to the direction in which the conductor that is the clamped object extends, it is possible to insert the front ends of the clamp arms into narrow gaps even more easily.

Also, with the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, the clamp arms are formed so that the thickness of the part corresponding to the front end of each sensor case that constructs the outer shells of the clamp arms is uniform (or substantially uniform) when viewed at the section. This means that according to the clamp sensor and the measuring device, compared to a configuration where the thickness of each sensor case is non-uniform, it is possible to avoid concentration of stress in parts of the sensor cases where the thickness is low and to increase the strength of the sensor cases. It is therefore possible to reliably avoid damage to the sensor cases when a load is applied to the sensor cases.

Also, according to the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, by forming the clamp arms so that the area of the section at the base end portions of the clamp arms is larger than the area of the section at the front end portions, compared to a configuration where the clamp arms are formed so that the area of the section at the front end portions and the area of the section at the base end portions are the same, it is possible to sufficiently increase the strength of the clamp arms.

Also, with the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, the clamp arms are formed so that the area of the outer form of the section at parts between the front ends and the boundary plane, which is perpendicular to the straight line (which passes the top end of the ring-shaped body and the centroid in plan view of the magnetic circuit) and passes a point in a range on the straight line that is centered on the centroid and has a length equivalent to 40% of the straight line distance from the top end to the centroid, is smaller than the area of the outer form of the section at parts between the boundary plane and the base ends. Here, when a plane that passes through a point that is close to the top end and is beyond the range of the length equivalent to 40% is defined as the boundary plane, the length of the front end portions whose area is small (that is, are narrow) is reduced, and when clamping one out of a large number of clamped objects disposed so as to be aligned side by side at narrow intervals, it is difficult to insert the front ends of the clamp arms deeply into the narrow gaps between the adjacent clamped objects. On the other hand, when a plane that passes through a point that is close to the base end and is beyond the range of the length equivalent to 40% is defined as the boundary plane, the length of the base end portions whose area is large (that is, are thick) is reduced, which lowers the strength of the clamp arms. Conversely, in this clamp sensor and the measuring device, since a plane that passes through the point defined within the range of the length equivalent to 40% is defined as the boundary plane, it is possible to easily insert the front ends of the clamp arms deeply into the narrow gaps between the adjacent clamped objects without reducing the strength of the clamp arms. Accordingly, by using the clamp sensor and the measuring device, the clamped object can be reliably clamped.

Also, with the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, the clamp arms are formed so that the area of the outer form of the section at parts between the front ends and the boundary plane, which is perpendicular to the straight line (which passes the top end of the ring-shaped body and the centroid in plan view of the inner circumference of the ring-shaped body) and passes a point in a range on the straight line that is centered on the centroid and has a length equivalent to 40% of the straight line distance from the top end to the centroid, is smaller than the area of the outer form of the section at parts between the boundary plane and the base ends. Here, when a plane that passes through a point that is close to the top end and is beyond the range of the length equivalent to 40% is defined as the boundary plane, the length of the front end portions whose area is small (that is, are narrow) is reduced, and when clamping one out of a large number of clamped objects disposed so as to be aligned side by side at narrow intervals, it is difficult to insert the front ends of the clamp arms deeply into the narrow gaps between the adjacent clamped objects. On the other hand, when a plane that passes through a point that is close to the base end and is beyond the range of the length equivalent to 40% is defined as the boundary plane, the length of the base end portions whose area is large (that is, are thick) is reduced, which lowers the strength of the clamp arms. Conversely, in this clamp sensor and the measuring device, since a plane that passes through the point defined within the range of the length equivalent to 40% is defined as the boundary plane, it is possible to easily insert the front ends of the clamp arms deeply into the narrow gaps between the adjacent clamped objects without reducing the strength of the clamp arms. Accordingly, by using the clamp sensor and the measuring device, the clamped object can be reliably clamped.

Also, with the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, the clamp arms are formed so that the first facing surfaces that construct the outer circumferential surface of the ring-shaped body at the front ends of the clamp arms are formed so as to produce a single flat surface that is perpendicular to a direction that connects the top end and the base end of the ring-shaped body in the state where the ring-shaped body is formed and the opposing distance between the first facing surfaces at the front ends is shorter than the opposing distance between the first facing surfaces at other parts of the clamp arms aside from the front ends. This means that according to the clamp sensor and the measuring device, the front ends of the clamp arms can be inserted even more easily into narrow gaps. Also, since the opposing distance between the first facing surfaces at the front ends is short, even when an obstacle such as a wall is present behind the clamped object and the gap between the clamped object and the obstacle is narrow, it is still possible to reliably clamp the clamped object while avoiding contact between the obstacle and the clamp arms.

Also, in the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, the clamp arms are formed so that the length along the straight line between the outer circumferential surface of the ring-shaped body and the position that is 15 mm from the center of the top end along a direction that is perpendicular to the straight line, which passes the top end of the ring-shaped body and the centroid, and parallel to the plane of the opening in the ring-shaped body, is within a range of at least 9 mm but no greater than 11 mm. Here, when the clamp arms are formed so that the above-described length exceeds 11 mm, the shape of the front end side of the clamp arms is too slender, so that as one example, when a clamed object disposed in the vicinity of a wall surface is to be clamped by the clamp arms, there is the risk of the front ends of the clamp arms contacting the wall surface, which makes clamping difficult. Also, when the clamp arms are formed so that the above-described length exceeds 11 mm, the top end side of the ring-shaped body will become extremely slender and the detection characteristics for the detected value may deteriorate. On the other hand, when the clamp arms are formed so that the above-described length is less than 9 mm, the shape of the front end side of the clamp arms will be close to an arc shape, and when attempting, for example, to clamp one out of a plurality of clamped objects disposed close to each other with the clamp arms, it is difficult to insert the front ends into gaps between other adjacent clamped objects, which makes clamping difficult. Conversely, with the clamp sensor and the measuring device, by forming the clamp arms so that the above-described length is within the range of at least 9 mm but no greater than 11 mm, it is possible to reliably clamp the clamped object while favorably maintaining the detection characteristics for magnetic fields.

Also, with the clamp sensor according to an aspect of this application and the measuring device according to an aspect of this application, the clamp arms are formed so that the longest distance between any two points on the outer form of the section in a part between the boundary plane and the front ends is within a range of at least 1/6 but no greater than 1/5 of the separation distance between the front ends of the clamp arms in a state where the front ends are separated by the maximum amount. Here, if the clamp arms are formed so that the above-described ratio exceeds 1/5, when clamping one out of a large number of clamped objects disposed side by side at narrow intervals, it is difficult to insert the front ends of the clamp arms into the narrow gaps between the adjacent clamped objects. On the other hand, when the clamp arms are formed so that the above-described ratio is less than 1/6, the separation distance in a state where the lever, which opens the clam arms (i.e., separates the front ends), is pressed in by the maximum amount and the front ends are separated by the maximum amount is too long, so that when a large number of clamped objects are disposed side by side at narrow intervals, there is the risk that a plurality of the clamped objects will be clamped. This may make it necessary for the user to vary how hard the lever is pressed, which results in poor operability. Conversely, with this clamp sensor and the measuring device, by forming the clamp arms so that the opposing distance is within the range of at least 1/6 but no greater than 1/5 of the separation distance, it is possible to easily insert the front ends into the narrow gaps between adjacent clamped objects in a state where the lever has been pressed in by the maximum amount. This means that while sufficiently improving operability, it is possible to clamp one out of a plurality of the clamped objects even more reliably.

FIG. 1 is a perspective view of a clamp meter 1 .

FIG. 2 is a block diagram depicting the configuration of the clamp meter 1 .

FIG. 3 is a perspective view of the clamp meter 1 when a clamp sensor 2 is in an opened state.

FIG. 4 is a front view of the clamp meter 1 .

FIG. 5 is a schematic front view of the clamp meter 1 in a state where sensor cases 10 a and 10 b , part of a main body case 30 , and the like have been removed.

FIG. 6 is a cross-sectional view that compares a section along a line A-A and a section along a line B-B in FIG. 4 .

FIG. 7 is a cross-sectional view along the line A-A in FIG. 4 .

FIG. 8 is a diagram useful in explaining the configuration of clamp arms 11 a and 11 b.

FIG. 9 is a front view of the clamp meter 1 in a state where the clamp arms 11 a and 11 b are in the opened state.

FIG. 10 is a first diagram useful in explaining a method of using the clamp meter 1 .

FIG. 11 is a second diagram useful in explaining a method of using the clamp meter 1 .

FIG. 12 is a third diagram useful in explaining a method of using the clamp meter 1 .

FIG. 13 is a front view of a clamp meter 1 A.

FIG. 14 is a cross-sectional view depicting the configuration of a clamp sensor 402 .

FIG. 15 is a cross-sectional view depicting the configuration of a clamp sensor 502 .

FIG. 16 is a cross-sectional view depicting the configuration of a clamp sensor 602 .

Preferred embodiments of a clamp sensor and a measuring device will now be described with reference to the attached drawings.

First, the configuration of a clamp meter 1 depicted in FIG. 1 will be described. The clamp meter 1 is one example of a measuring device, and is configured so as to be capable of contactlessly (i.e., without metal-metal contact) measuring the current (one example of a “measured value”) flowing in a conductor 400 as one example of a clamped object, which is depicted in FIG. 10 . In more detail, as depicted in FIGS. 1 to 3 , the clamp meter 1 is equipped with a clamp sensor 2 and a main body 3 .

As depicted in FIGS. 1 and 3 , the clamp sensor 2 includes a pair of clamp arms 11 a and 11 b (hereinafter, collectively referred to as the “clamp arms 11 ” when no distinction is made between them), and as depicted in FIG. 4 , in a state where the conductor 400 is clamped by (that is, surrounded by) the clamp arms 11 a and 11 b , a magnetic field is contactlessly detected as a detected value produced when a current flows in the conductor 400 .

Also, with this clamp sensor 2 , as depicted in FIGS. 1 and 3 , the clamp arm 11 b (which is one of the clamp arms 11 a and 11 b ) is configured so as to be rotatable about a rotational shaft 23 (see FIG. 4 ) so that front ends 21 a and 21 b of the clamp arms 11 a and 11 b open and close (i.e., come in to contact and move apart). The clamp arm 11 a is fixed to a main body case 30 of the main body 3 in a non-rotatable state. The clamp sensor 2 is also configured so that the clamp arm 11 b rotates in response to operations (pressing, or the releasing of pressing) of a lever 30 a disposed on the main body case 30 . Note that in the following description, a state where the front ends 21 a and 21 b of the clamp arms 11 a and 11 b are closed (the state depicted in FIG. 1 ) is referred to as the “closed state” and a state where the front ends 21 a and 21 b have been opened (the state depicted in FIGS. 3 and 9 ) is referred to as the “opened state”.

As depicted in FIG. 4 , the clamp arm 11 a includes a sensor case 10 a , a core 41 (see FIGS. 5 and 7 ) housed inside the sensor case 10 a , and a magnetic detection element (as one example, a Hall element), not illustrated. As depicted in FIG. 4 , the clamp arm 11 b includes a sensor case 10 b and a core 41 (see FIGS. 5 and 7 ) housed inside the sensor case 10 b.

As depicted in FIG. 4 , the clamp arms 11 a and 11 b are both formed so as to be substantially arc-shaped in plan view, that is, when looking in the thickness direction (which is the axial direction of the rotational shaft 23 ), so as to form a ring-shaped body 100 when the front ends 21 a and 21 b are closed. Here, as depicted in the drawings, an inner circumferential surface on a base end 100 b side of the ring-shaped body 100 is formed in a semicircular shape in plan view by parts on the respective base ends 22 a and 22 b sides of the clamp arms 11 a and 11 b (these parts are hereinafter also referred to as the “base end portions 52 a and 52 b ”) and a top end 100 a (that is, parts corresponding to the front ends 21 a and 21 b ) side of the ring-shaped body 100 is formed as a slender ring-shape that is arc-shaped in plan view by parts on the front ends 21 a and 21 b sides of the clamp arms 11 a and 11 b (hereinafter, these parts are also referred to as the “front end portions 51 a and 51 b ”). The inner circumferential surface on the top end 100 a side also has a smaller curvature (that is, a larger radius of curvature) than the inner circumferential surface on the base end 100 b side.

As depicted in FIG. 5 , in the state where the ring-shaped body 100 is formed, the cores 41 of the clamp arms 11 a and 11 b form a ring-shaped (that is, substantially oval) magnetic circuit Mc. In this state, when a current flows in the conductor 400 surrounded (or “clamped”) by the clamp arms 11 a and 11 b , the current produces a magnetic field in the magnetic circuit Mc, which is detected by the magnetic detection element in the clamp arm 11 a.

As depicted in FIG. 6 , the clamp arms 11 a and 11 b are formed so that the outer form of a section Sc 1 (as on example, the cross section along the line A-A in FIG. 4 ) of the front end portions 51 a and 51 b taken perpendicular to the length direction is substantially octagonal, for example, and the outer form of a section Sc 2 (for example, a cross section taken along the line B-B in FIG. 4 ) of the base end portions 52 a and 52 b taken perpendicular to the length direction is substantially rectangular. In addition, as depicted in FIG. 6 , the clamp arms 11 a and 11 b are formed so that the area Sa 1 of the outer form of the section Sc 1 at the front end portions 51 a and 51 b is smaller than the area Sa 2 (hereinafter, when no distinction is made between the areas Sa 1 and Sa 2 , the expression “area Sa” is used) of the outer form of the section Sc 2 at the base end portions 52 a and 52 b , that is, so that the area Sa 2 is larger than the area Sa 1 . In other words, the clamp arms 11 a and 11 b are formed so that the front end portions 51 a and 51 b are thinner than the base end portions 52 a and 52 b.

In this the clamp sensor 2 , the front end portions 51 a and 51 b and the base end portions 52 a and 52 b are defined as follows. First, as depicted in FIG. 5 , a straight line H 1 that passes the top end 100 a of the ring-shaped body 100 and a centroid C 1 in plan view (depicted by the dotted lines in FIG. 5 ) of the magnetic circuit Mc formed by the cores 41 is defined. Next, a length L 101 equivalent to 40% of a distance D 101 (the straight line distance) from the top end 100 a (in more detail, an outer facing surface 101 at the top end 100 a ) to the centroid C 1 is specified, and any point (hereinafter, also referred to the “defined point P 101 ”) is defined on the straight line H 1 in a range that is centered on the centroid C 1 and has the length L 101 . Here, in this example, a point separated from the centroid C 1 toward the top end 100 a by a length corresponding to 17% of the distance D 101 is defined as the “defined point P 101 ”. After this, a plane that passes through the defined point P 101 and is perpendicular to the straight line H 1 is defined as a “boundary plane Sb 1 ”, the parts between the boundary plane Sb 1 and the front ends 21 a and 21 b of the clamp arms 11 a and 11 b are defined as the “front end portions 51 a and 51 b ” and the parts between the boundary plane Sb 1 and the base ends 22 a and 22 b are defined as the “base end portions 52 a and 52 b”.

As depicted in FIGS. 1, 3, and 4 , the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b have a pair of facing surfaces 101 that construct the outer circumferential surface and the inner circumferential surface of the ring-shaped body 100 (and correspond to “first facing surfaces”), a pair of facing surfaces 102 that construct two side surfaces of the ring-shaped body 100 (and correspond to “second facing surfaces”), and a pair of facing surfaces 103 and a pair of facing surfaces 104 that are inclined to the facing surfaces 101 and 102 (both correspond to “third facing surfaces” and in total are two pairs of “third facing surfaces” as one example of a “plurality of pairs”). As depicted in FIG. 7 , the front end portions 51 a and 51 b are formed so that the outer form of the section Sc 1 (the cross section along the line A-A in FIG. 4 ) taken perpendicular to the length direction of the clamp arms 11 a and 11 b is octagonal or substantially octagonal. In other words, the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed as octagonal pillars where the corners of a rectangular pillar depicted by the broken lines in FIG. 7 have been chamfered (the facing surfaces 103 and 104 correspond to surfaces (chamfered surfaces) formed by chamfering). Note that since the front end portions 51 a and 51 b have the same cross-sectional form, in FIG. 7 , only the cross-sectional form of the front end portion 51 a is illustrated and the cross-sectional form of the front end portion 51 b is omitted.

In this clamp sensor 2 , as depicted in FIG. 7 , parts of the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b aside from the front ends 21 a and 21 b are formed so that out of the edges of the octagon that is the outer form of the section Sc 1 , the edges E 1 corresponding to the facing surfaces 101 and the edges E 2 corresponding to the facing surfaces 102 are formed with the same length L 1 , and the length of the edges E 3 corresponding to the facing surfaces 103 (that is, the length of a segment that joins both ends of an edge E 3 ) and the length of the edges E 4 corresponding to the facing surfaces 104 (that is, the length of a segment that joins both ends of an edge E 4 ) are formed with the same length L 2 . In addition, in the clamp sensor 2 , as depicted in FIG. 7 , the front end portions 51 a and 51 b are formed so that the length L 2 is longer than the length L 1 (the shortest length out of the lengths of the edges E 1 and E 2 ).

Note that in the example depicted in FIG. 7 , since the edges E 3 and E 4 are both straight, the lengths of the segments that join both ends of the edges E 3 and E 4 are the same as the edges E 3 and E 4 . However, it is also possible to use a configuration where the edges E 3 and E 4 are curved (arc-shaped) (a configuration where the outer form of the section Sc 1 is substantially octagonal), and for this configuration, the length of a segment that joins both ends of the edges E 3 and E 4 is treated as the length L 2 and the front end portions 51 a and 51 b are formed so that the length L 2 is longer than the length L 1 (the shortest length out of the lengths of the edges E 1 and E 2 ).

In this clamp sensor 2 , by defining the length L 1 of the edges E 1 and E 2 and the length L 2 of the edges E 3 and E 4 as described above, as depicted in FIG. 7 , the front end portions 51 a and 51 b are formed so that an opposing distance D 3 between the edges E 3 and an opposing distance D 4 between the edges E 4 are shorter than an opposing distance D 1 between the edges E 1 and an opposing distance D 2 between the edges E 2 .

In this clamp sensor 2 , as depicted in FIG. 7 , the sensor cases 10 a and 10 b that construct outer shells of the clamp arms 11 a and 11 b are formed so that the thickness T of parts corresponding to the front end portions 51 a and 51 b (hereinafter, referred to as “front end parts of the sensor cases 10 a and 10 b ”) is uniform (or substantially uniform) when viewed at the section Sc 1 .

In this clamp sensor 2 , as depicted in FIG. 8 , the facing surfaces 101 on the outer circumferential sides of the front ends 21 a and 21 b of the clamp arms 11 a and 11 b (that is, the facing surfaces 101 that construct the outer circumferential surface of the ring-shaped body 100 ) are formed so as to produce a single flat surface that is perpendicular to a direction (the vertical direction in FIG. 8 ) that connects the top end 100 a and the base end 100 b in the state where the ring-shaped body 100 is formed. That is, one part of the outer circumference (the portion indicated by the broken line in FIG. 8 ) of the top end 100 a of the ring-shaped body 100 is cut away on a flat plane. By forming the clamp sensor 2 in this way, as depicted in FIG. 8 , the clamp arms 11 a and 11 b are formed so that the opposing distance D 1 between the facing surfaces 101 at the front ends 21 a and 21 b (hereinafter, this particular opposing distance D 1 is also referred to as the “opposing distance D 1 a ”) is shorter than the opposing distance D 1 between the facing surfaces 101 at other parts of the clamp arms 11 a and 11 b aside from the front ends 21 a and 21 b (hereinafter, that opposing distance D 1 is also referred to as the “opposing distance D 1 b ”). This means that for this clamp sensor 2 , the length of the ring-shaped body 100 along the direction that connects the top end 100 a and the base end 100 b is shorter by the reduction in the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b.

Also, in this clamp sensor 2 , as depicted in FIG. 8 , the clamp arms 11 a and 11 b are formed so that a length L 103 along the straight line H 1 between the outer facing surface 101 of the ring-shaped body 100 and a position P that is 15 mm (hereinafter, this length is also referred to as “the length L 102 ”) from the center of the top end 100 a along a direction that is perpendicular to the straight line H 1 described above and parallel to the plane of the opening F in the ring-shaped body 100 is within a range of at least 9 mm but no greater than 11 mm. That is, the clamp arms 11 a and 11 b are formed so that the ratio of the length L 103 to the length L 102 is within a range of at least 9/15 but no greater than 11/15.

Here, as one example, when the clamp arms 11 a and 11 b are formed so that the length L 103 exceeds 11 mm, the shape of the front ends 21 a and 21 b sides of the clamp arms 11 a and 11 b is too slender, so that as one example, when a conductor 400 disposed in the vicinity of a wall surface (that is, a wall surface is present to the rear) is to be clamped by the clamp arms 11 a and 11 b , there is the risk of the front ends 21 a and 21 b of the clamp arms 11 a and 11 b contacting the wall surface, which makes clamping difficult. Also, when the clamp arms 11 a and 11 b are formed so that the length L 103 exceeds 11 mm, the top end 100 a of the ring-shaped body 100 will become extremely slender and the detection characteristics for magnetic fields (the detected value) may deteriorate. On the other hand, when the clamp arms 11 a and 11 b are formed so that the length L 103 is less than 9 mm, the shape of the front ends 21 a and 21 b sides of the clamp arms 11 a and 11 b will be close to an arc shape, and when attempting, for example, to clamp one conductor 400 out of a plurality of conductors 400 disposed close to each other with the clamp arms 11 a and 11 b , it is difficult to insert the front ends 21 a and 21 b into gaps between other adjacent conductors 400 , which makes clamping difficult. Conversely, with the clamp sensor 2 , by forming the clamp arms 11 a and 11 b so that the length L 103 along the straight line H 1 between the outer facing surface 101 of the ring-shaped body 100 and the position P that is 15 mm from the center of the top end 100 a along a direction that is perpendicular to the straight line H 1 and parallel to the plane of the opening F in the ring-shaped body 100 is within the range of at least 9 mm but no greater than 11 mm, it becomes possible to reliably clamp a conductor 400 while favorably maintaining the detection characteristics for magnetic fields.

Also, with the clamp sensor 2 , as depicted in FIG. 9 , the clamp arms 11 a and 11 b are formed so that when the longest distance out of straight line distances between any two points on the outer form of the section Sc 1 at the front end portions 51 a and 51 b is set as the opposing distance D 1 (see FIG. 7 ) and a distance between the front ends 21 a and 21 b of the clamp arms 11 a and 11 b in a state where the front ends 21 a and 21 b are separated by the maximum amount is set as the separation distance D 102 , the ratio R of the opposing distance D 1 to the separation distance D 102 is within a range of at least 1/6 but no greater than 1/5. Note that for this clamp sensor 2 , as one example, the separation distance D 102 is defined within a range of 56.8 mm±25%, and the opposing distance D 1 is defined within a range of 11 mm±25%.

When the clamp arms 11 a and 11 b are formed so that the ratio R exceeds 1/5, as one example, as depicted in FIG. 10 , when clamping one out of a large number of conductors 400 disposed side by side at narrow intervals, it was clear from the results of experiments by the present inventors that it is difficult to insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the narrow gaps G 1 and G 2 between the adjacent conductors 400 . On the other hand, when the clamp arms 11 a and 11 b are formed so that the ratio R is less than 1/6, the separation distance D 102 in the state where the front ends 21 a and 21 b are separated by the maximum amount, that is, when the lever 30 a is pressed in by the maximum amount, is too long, so that when a large number of conductors 400 are disposed side by side at narrow intervals, there is the risk that a plurality of the conductors 400 will be clamped when attempting to clamp just one of the conductors 400 . This may make it necessary for the user to vary how hard the lever 30 a is pressed, which results in poor operability. Conversely, with this clamp sensor 2 , by forming the clamp arms 11 a and 11 b so that the ratio R is within the range of at least 1/6 but no greater than 1/5, it is possible to easily insert the front ends 21 a and 21 b into the narrow gaps G 1 and G 2 between adjacent conductors 400 in a state where the lever 30 a has been pressed in by the maximum amount. This means that with the clamp sensor 2 , it is not necessary to vary how hard the lever 30 a is pressed, which sufficiently improves operability.

In the clamp sensor 2 , as described above, the base end portions 52 a and 52 b of the clamp arms 11 a and 11 b are formed so as to be substantially rectangular in cross-section, and as depicted in FIG. 4 , the clamp arms 11 a and 11 b are formed so that the front end portions 51 a and 51 b are narrower than the base end portions 52 a and 52 b , that is, as depicted in FIG. 6 , so that the area Sa 1 of the outer form of the section Sc 1 at the front end portions 51 a and 51 b is smaller than the area Sa 2 of the outer form of the section Sc 2 at the base end portions 52 a and 52 b . In other words, the clamp arms 11 a and 11 b are formed so that the base end portions 52 a and 52 b are thicker than the front end portions 51 a and 51 b , that is, the area of the section Sc 2 at the base end portions 52 a and 52 b is larger than the area of the section Sc 1 at the front end portions 51 a and 51 b . This means that with this clamp sensor 2 , compared to a configuration where clamp arms 11 a and 11 b are formed so that the area of the section Sc 1 at the front end portions 51 a and 51 b is the same as the area of the section Sc 2 at the base end portions 52 a and 52 b , the strength of the clamp arms 11 a and 11 b is sufficiently increased.

Also, as described above, in the clamp sensor 2 , parts between the front ends 21 a and 21 b and the boundary plane Sb 1 , which is perpendicular to the straight line H 1 and passes the defined point P 101 (defined in a range centered on the centroid C 1 in plan view of the magnetic circuit Mc and having a length L 101 equivalent to 40% of the distance D 101 from the top end 100 a to the centroid C 1 ), are defined as the front end portions 51 a and 51 b and parts between the base ends 22 a and 22 b and the boundary plane Sb 1 are defined as the base end portions 52 a and 52 b . When a plane that passes through a point that is close to the top end 100 a and is beyond the range of the length L 101 is defined as the boundary plane Sb 1 , the length of the front end portions 51 a and 51 b whose area Sa is small (that is, are narrow) is reduced, and when clamping one out of a large number of conductors 400 disposed so as to be aligned side by side at narrow intervals, it is difficult to insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b deeply into the narrow gaps G 1 and G 2 between adjacent conductors 400 . On the other hand, when a plane that passes through a point that is close to the base end 100 b and is beyond the range of the length L 101 is defined as the boundary plane Sb 1 , the length of the base end portions 52 a and 52 b whose area Sa is large (that is, are thick) is reduced, which lowers the strength of the clamp arms 11 a and 11 b . Conversely, in this clamp sensor 2 , since a plane that passes through the defined point P 101 defined within the range of the length L 101 is defined as the boundary plane Sb 1 , it is possible to easily insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b deeply into the narrow gaps G 1 and G 2 between adjacent conductors 400 without reducing the strength of the clamp arms 11 a and 11 b.

As depicted in FIG. 2 , the main body 3 includes a display 31 , an operator 32 , a processor 33 , and the main body case 30 (see FIGS. 1, 3, and 4 ) where these components are housed or disposed.

The display 31 is composed of a liquid crystal panel for example, and is disposed on a front panel of the main body case 30 as depicted in FIGS. 1, 3, and 4 . The display 31 displays a measured value of current and the like according to control by the processor 33 . The operator 32 is configured to include various switches 32 a , dials 32 b , and the like disposed on the front panel of the main body case 30 , and outputs operation signals in keeping with operations of these parts.

The processor 33 controls the components that construct the main body 3 according to the operation signals outputted from the operator 32 . The processor 33 functions as a meter, measures a current value of the current flowing through the conductor 400 based on the detection signal outputted from the clamp sensor 2 (the magnetic detection element), and displays the current value on the display 31 .

Next, a method of using the clamp meter 1 and operations of the clamp meter 1 when doing so will be described with reference to the drawings. As one example, a usage method when measuring the current value of the current flowing through one (for example, the conductor 400 a in FIG. 10 ) out of a plurality of conductors 400 disposed side by side at narrow intervals as depicted in FIG. 10 will be described. In this example, it is assumed that a plurality of conductors 400 with a diameter of 21 mm are disposed side by side at intervals of 12 mm (so that the gaps between the adjacent conductors 400 are 12 mm).

First, the lever 30 a (see FIGS. 1 and 4 ) on the main body 3 of the clamp meter 1 is pressed in. At this time, the clamp arm 11 b rotates in a direction where the front ends 21 a and 21 b of the clamp arms 11 a and 11 b of the clamp sensor 2 open up against the biasing force of a spring (not illustrated), thereby placing the clamp arms 11 a and 11 b in the opened state as depicted in FIG. 3 .

Next, as depicted in FIG. 10 , the front ends 21 a and 21 b of the clamp arms 11 a and 11 b are brought close to the conductor 400 a to be measured (the “clamped object”). After this, as depicted in FIG. 11 , the clamp meter 1 is tilted so as to rotate with the length direction of the clamp meter 1 (the direction that connects the top end 100 a and the base end 100 b of the ring-shaped body 100 depicted in FIG. 4 ) as the rotational axis, the front end 21 a of the clamp arm 11 a is inserted into the gap G 1 between the conductor 400 a and a conductor 400 b adjacent on the right of the conductor 400 a , and the front end 21 b of the clamp arm 11 b is inserted into the gap G 2 between the conductor 400 a and a conductor 400 c adjacent on the left of the conductor 400 a.

Here, as depicted by the broken lines in FIG. 7 , with the conventional configuration where the outer form of the section Sc 1 at each of the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b is rectangular (that is, a configuration where the corners of a rectangular pillar are not chamfered), the distance (the diagonal distance D 5 depicted in FIG. 7 ) between opposing corners of the rectangle that is the outer form of the section Sc 1 is longer than the opposing distance D 1 between the edges E 1 and the opposing distance D 2 between the edges E 2 . This means that with the conventional configuration, when the gap G 1 between the conductors 400 a and 400 b and the gap G 2 between the conductors 400 a and 400 c are narrow as depicted in FIG. 11 , it is difficult to insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the respective gaps G 1 and G 2 when the clamp meter 1 is tilted.

On the other hand, with the clamp sensor 2 , as described above, the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed as octagonal pillars where the outer form of the section Sc 1 is octagonal due to the corners of a rectangular pillar being chamfered, and the length L 2 of the edges E 3 and E 4 of the octagon that is the outer form of the section Sc 1 is longer than the length L 1 of the edges E 1 and E 2 . This means that in this clamp sensor 2 , the opposing distance D 3 between the edges E 3 and the opposing distance D 4 between the edges E 4 are shorter than the opposing distance D 1 between the edges E 1 and the opposing distance D 2 between the edges E 2 . Accordingly, with this clamp sensor 2 , compared to the conventional configuration, it is possible to easily insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the narrow gaps G 1 and G 2 in a state where the clamp meter 1 is tilted.

Also, with the clamp sensor 2 , as described above, since the clamp arms 11 a and 11 b are formed so that the ratio R of the opposing distance D 1 , which is the longest distance between any two points on the outer form of the section Sc 1 at the front end portions 51 a and 51 b , to the separation distance D 102 , which is the distance between the front ends 21 a and 21 b of the clamp arms 11 a and 11 b in a state where the front ends 21 a and 21 b are separated by the maximum amount, is within a range of at least 1/6 but no greater than 1/5, in a state where the lever 30 a is pressed in by the maximum amount, it is possible to easily insert the front ends 21 a and 21 b into the narrow gaps G 1 and G 2 between the adjacent conductors 400 . This means that with the clamp sensor 2 , it is not necessary to vary how hard the lever 30 a is pressed, which makes it possible to sufficiently improve operability.

After this, in a state where the front ends 21 a and 21 b of the clamp arms 11 a and 11 b have been inserted into the gaps G 1 and G 2 , respectively, the pressing of the lever 30 a is released. At this time, due to the biasing force of the spring (not illustrated), the clamp arm 11 b rotates in a direction where the front ends 21 a and 21 b of the clamp arms 11 a and 11 b come into contact, which produces the closed state of the clamp arms 11 a and 11 b as depicted in FIG. 12 . By doing so, the conductor 400 a is clamped by the clamp arms 11 a and 11 b as depicted in FIG. 12 .

Here, with this clamp sensor 2 , as described above, parts between the front ends 21 a and 21 b of the clamp arms 11 a and 11 b and the boundary plane Sb 1 , which passes the defined point P 101 (defined in a range with a length L 101 equivalent to 40% of the distance D 101 from the top end 100 a to the centroid C 1 in plan view of the magnetic circuit Mc), are defined as the front end portions 51 a and 51 b , parts between the base ends 22 a and 22 b of the clamp arms 11 a and 11 b and the boundary plane Sb 1 are defined as the base end portions 52 a and 52 b , and the clamp arms 11 a and 11 b are formed so that the area Sa 1 of the outer form of the section Sc 1 at the front end portions 51 a and 51 b is smaller than the area Sa 2 of the outer form of the section Sc 2 at the base end portions 52 a and 52 b . This means that with the clamp sensor 2 , the front ends 21 a and 21 b of the clamp arms 11 a and 11 b can be easily inserted deeply into the narrow gaps G 1 and G 2 between the adjacent conductors 400 without reducing the strength of the clamp arms 11 a and 11 b . Accordingly, it is possible to reliably clamp the conductor 400 a with the clamp sensor 2 .

The magnetic detection element disposed on the clamp arm 11 a then detects the magnetic field that has been generated in the cores of the clamp arms 11 a and 11 b by the current flowing through the conductor 400 a , and outputs a detection signal. Here, in the clamp sensor 2 , as described above, the clamp arms 11 a and 11 b are formed so that the length L 103 along the straight line H 1 between the outer facing surface 101 of the ring-shaped body 100 and the position P that is 15 mm from the center of the top end 100 a along a direction that is perpendicular to the straight line H 1 and parallel to the plane of the opening F in the ring-shaped body 100 is within the range of at least 9 mm but no greater than 11 mm. This means that the clamp sensor 2 is capable of maintaining favorable detection characteristics for magnetic fields. Accordingly, the clamp sensor 2 is capable of outputting a detection signal capable of accurately measuring the current flowing through the conductor 400 a . After this, the processor 33 of the main body 3 measures the current value of the current flowing through the conductor 400 a based on the detection signal. The processor 33 then displays the measured value on the display 31 .

Next, when measurement has been completed, the lever 30 a is pressed in to open the clamp arms 11 a and 11 b , and then the clamp sensor 2 is pulled away from the conductor 400 a . After this, the pressing of the lever 30 a is released, which places the clamp arms 11 a and 11 b in the closed state.

In this way, with the clamp sensor 2 and the clamp meter 1 , the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed so that out of the edges constructing the outer form (in this example, an octagonal or substantially octagonal shape) of the section Sc 1 , the length L 2 of the edges E 3 and E 4 (or the length L 2 of a segment that joins both ends of an edge E 3 or E 4 ) is longer than the length L 1 of the edges E 1 and E 2 . This means that in the clamp sensor 2 and the clamp meter 1 , the opposing distance D 3 between the edges E 3 and the opposing distance D 4 between the edges E 4 can be made shorter than the opposing distance D 1 between the edges E 1 and the opposing distance D 2 between the edges E 2 . As a result, according to the clamp sensor 2 and the clamp meter 1 , compared to the conventional configuration in which the outer form of the section Sc 1 at each of the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b is rectangular and the diagonal distance D 5 of the section Sc 1 is longer than the opposing distance D 1 between the edges E 1 and the opposing distance D 2 between the edges E 2 (that is, a configuration where the corners of a rectangular pillar are not chamfered), it is possible to easily insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the narrow gaps G 1 and G 2 in a state where the clamp meter 1 is tilted. Accordingly, with the clamp sensor 2 and the clamp meter 1 , the conductor 400 that is the clamped object can be reliably clamped, even when another conductor 400 or an obstacle is present in the vicinity of the conductor 400 that is the clamped object.

Also, according to the clamp sensor 2 and the clamp meter 1 , by forming the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b so that the length L 2 of all of the edges E 3 and E 4 (or the length L 2 of every line segment that joins both ends of an edge E 3 or E 4 ) is longer than the length L 1 of the edges E 1 and E 2 , it is possible to make both the opposing distance D 3 between the edges E 3 and the opposing distance D 4 between the edges E 4 shorter than the opposing distance D 1 between the edges E 1 and the opposing distance D 2 between the edges E 2 . This means that even when the clamp meter 1 is tilted so as to rotate in either of the clockwise or counterclockwise directions with the length direction of the clamp meter 1 as the axis, it is possible to easily insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the narrow gaps G 1 and G 2 .

Also, with the clamp sensor 2 and the clamp meter 1 , the clamp arms 11 a and 11 b are formed so that the thickness T of the front end parts of the sensor cases 10 a and 10 b that construct the outer shells of the clamp arms 11 a and 11 b is uniform (or substantially uniform) when viewed at the section Sc 1 . This means that according to the clamp sensor 2 and the clamp meter 1 , compared to a configuration where the thickness T of the front end parts of the sensor cases 10 a and 10 b is non-uniform, it is possible to avoid concentration of stress in parts of the sensor cases 10 a and 10 b where the thickness is low and to increase the strength of the sensor cases 10 a and 10 b . It is therefore possible to reliably avoid damage to the sensor cases 10 a and 10 b when a load is applied to the sensor cases 10 a and 10 b.

According to the clamp sensor 2 and the clamp meter 1 , by forming the clamp arms 11 a and 11 b so that the area of the section Sc 2 at the base end portions 52 a and 52 b is larger than the area of the section Sc 1 at the front end portions 51 a and 51 b , compared to a configuration where the clamp arms 11 a and 11 b are formed so that the area of the section Sc 1 at the front end portions 51 a and 51 b and the area of the section Sc 2 at the base end portions 52 a and 52 b are the same, it is possible to sufficiently increase the strength of the clamp arms 11 a and 11 b.

Also, with the clamp sensor 2 and the clamp meter 1 , the clamp arms 11 a and 11 b are formed so that the area Sa 1 of the outer form of the section Sc 1 at the front end portions 51 a and 51 b between the front ends 21 a and 21 b and the boundary plane Sb 1 , which is perpendicular to the straight line H 1 (which passes the top end 100 a of the ring-shaped body 100 and the centroid C 1 in plan view of the magnetic circuit Mc) and passes a point in a range on the straight line H 1 that is centered on the centroid C 1 and has a length L 101 equivalent to 40% of the distance D 101 from the top end 100 a to the centroid C 1 , is smaller than the area Sa 2 of the outer form of the section Sc 2 at the base end portions 52 a and 52 b between the boundary plane Sb 1 and the base ends 22 a and 22 b . Here, when a plane that passes through a point that is close to the top end 100 a and is beyond the range of the length L 101 is defined as the boundary plane Sb 1 , the length of the front end portions 51 a and 51 b whose area Sa 1 is small (that is, narrow) is reduced, and when clamping one out of a large number of conductors 400 disposed so as to be aligned side by side at narrow intervals, it is difficult to insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b deeply into the narrow gaps G 1 and G 2 between the adjacent conductors 400 . On the other hand, when a plane that passes through a point that is close to the base end 100 b and is beyond the range of the length L 101 is defined as the boundary plane Sb 1 , the length of the base end portions 52 a and 52 b whose area Sa 2 is large (that is, thick) is reduced, which lowers the strength of the clamp arms 11 a and 11 b . Conversely, in this clamp sensor 2 , since a plane that passes through the defined point P 101 defined within the range of the length L 101 is defined as the boundary plane Sb 1 , it is possible to easily insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b deeply into the narrow gaps G 1 and G 2 between the adjacent conductors 400 without reducing the strength of the clamp arms 11 a and 11 b . Accordingly, by using the clamp sensor 2 , the conductor 400 a can be reliably clamped.

Also, with the clamp sensor 2 and the clamp meter 1 , the clamp arms 11 a and 11 b are formed so that the facing surfaces 101 on the outer circumferential sides of the front ends 21 a and 21 b of the clamp arms 11 a and 11 b are formed so as to produce a single flat surface that is perpendicular to a direction that connects the top end 100 a and the base end 100 b of the ring-shaped body 100 in the state where the ring-shaped body 100 is formed and the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b is shorter than the opposing distance D 1 b between the facing surfaces 101 at other parts of the clamp arms 11 a and 11 b aside from the front ends 21 a and 21 b . This means that according to the clamp sensor 2 and the clamp meter 1 , the front ends 21 a and 21 b of the clamp arms 11 a and 11 b can be inserted even more easily into the narrow gaps G 1 and G 2 . Also, since the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b is short, even when an obstacle such as a wall is present behind the conductor 400 that is the clamped object and the gap between the conductor 400 and the obstacle is narrow, it is still possible to reliably clamp the conductor 400 that is the clamped object while avoiding contact between the obstacle and the clamp arms 11 a and 11 b.

Also, in the clamp sensor 2 and the clamp meter 1 , the clamp arms 11 a and 11 b are formed so that the length L 103 along the straight line H 1 between the outer facing surface 101 of the ring-shaped body 100 and the position P that is 15 mm from the center of the top end 100 a along a direction that is perpendicular to the straight line H 1 and parallel to the plane of the opening F in the ring-shaped body 100 is within the range of at least 9 mm but no greater than 11 mm. Here, when the clamp arms 11 a and 11 b are formed so that the length L 103 exceeds 11 mm, the shape of the front ends 21 a and 21 b sides of the clamp arms 11 a and 11 b is too slender, so that as one example, when a conductor 400 disposed in the vicinity of a wall surface is to be clamped by the clamp arms 11 a and 11 b , there is the risk of the front ends 21 a and 21 b of the clamp arms 11 a and 11 b contacting the wall surface, which makes clamping difficult. Also, when the clamp arms 11 a and 11 b are formed so that the length L 103 exceeds 11 mm, the top end 100 a side of the ring-shaped body 100 will become extremely slender and the detection characteristics for magnetic fields (the detected value) may deteriorate. On the other hand, when the clamp arms 11 a and 11 b are formed so that the length L 103 is less than 9 mm, the shape of the front ends 21 a and 21 b sides of the clamp arms 11 a and 11 b will be close to an arc shape, and when attempting, for example, to clamp one conductor 400 out of a plurality of conductors 400 disposed close to each other with the clamp arms 11 a and 11 b , it is difficult to insert the front ends 21 a and 21 b into gaps between other adjacent conductors 400 , which makes clamping difficult. Conversely, with the clamp sensor 2 , by forming the clamp arms 11 a and 11 b so that the length L 103 is within the range of at least 9 mm but no greater than 11 mm, it is possible to reliably clamp a conductor 400 while favorably maintaining the detection characteristics for magnetic fields.

With the clamp sensor 2 and the clamp meter 1 , the clamp arms 11 a and 11 b are formed so that the opposing distance D 1 that is the longest distance between any two points on the outer form of the section Sc 1 at the front end portions 51 a and 51 b is within a range of at least 1/6 but no greater than 1/5 of the separation distance D 102 between the front ends 21 a and 21 b of the clamp arms 11 a and 11 b in a state where the front ends 21 a and 21 b are separated by the maximum amount. Here, if the clamp arms 11 a and 11 b are formed so that the ratio R exceeds 1/5, when clamping one out of a large number of conductors 400 disposed side by side at narrow intervals, it is difficult to insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the narrow gaps G 1 and G 2 between the adjacent conductors 400 . On the other hand, when the clamp arms 11 a and 11 b are formed so that the ratio R is less than 1/6, the separation distance D 102 in a state where the lever 30 a is pressed in by the maximum amount and the front ends 21 a and 21 b are separated by the maximum amount is too long, so that when a large number of conductors 400 are disposed side by side at narrow intervals, there is the risk that a plurality of the conductors 400 will be clamped. This may make it necessary for the user to vary how hard the lever 30 a is pressed, which results in poor operability. Conversely, with this clamp sensor 2 , by forming the clamp arms 11 a and 11 b so that the opposing distance D 1 is within the range of at least 1/6 but no greater than 1/5 of the separation distance D 102 , it is possible to easily insert the front ends 21 a and 21 b into the narrow gaps G 1 and G 2 between adjacent conductors 400 in a state where the lever 30 a has been pressed in by the maximum amount. This means that while sufficiently improving operability, it is possible to clamp one out of a plurality of the conductors 400 even more reliably.

Note that the configurations of the clamp sensor and the measuring device are not limited to the configurations described above. As one example, although an example where only the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed so that the outer form of the section Sc 1 is octagonal, the length L 2 of the edges E 3 and E 4 out of the edges of the octagon are longer than the length L 1 of the edges E 1 and E 2 and the base end portions 52 a and 52 b of the clamp arms 11 a and 11 b are formed so as to be substantially rectangular in cross-section, it is also possible to use a configuration where both the front end portions 51 a and 51 b and the base end portions 52 a and 52 b of the clamp arms 11 a and 11 b are formed with the shape described earlier. By using this configuration, it becomes easy to insert both the front end portions 51 a and 51 b and the base end portions 52 a and 52 b of the clamp arms 11 a and 11 b into narrow gaps.

It is also possible to use a configuration where both the front end portions 51 a and 51 b and the base end portions 52 a and 52 b of the clamp arms 11 a and 11 b are formed so that the edges E 3 and E 4 are both curved (arc-shaped).

Also, although an example where the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed so that the edges E 1 and E 2 of the octagon, which is the outer form of the section Sc 1 , have the same length L 1 and the edges E 3 and E 4 have the same length L 2 has been described above, it is also possible to use a configuration where the front end portions 51 a and 51 b (or both the front end portions 51 a and 51 b and the base end portions 52 a and 52 b ) of the clamp arms 11 a and 11 b are formed so that the edges E 1 and E 2 are different lengths and/or the edges E 3 and E 4 are different lengths.

Also, although an example where the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed so that the length L 2 of all of the edges E 3 and E 4 is longer than the length L 1 of the edges E 1 and E 2 has been described, so long as a condition that the length of at least one out of the edges E 3 and E 4 is longer than the shortest length out of the edges E 1 and E 2 is satisfied, it is possible to arbitrarily set the lengths of the edges E 1 , E 2 , E 3 , and E 4 .

Also, although an example where the clamp arms 11 a and 11 b are formed so that one part of the outer circumference of the top end 100 a of the ring-shaped body 100 (the portion indicated by the broken line in FIG. 8 ) is cut away so that the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b is shorter than the opposing distance D 1 b between the facing surfaces 101 at other parts of the clamp arms 11 a and 11 b aside from the front ends 21 a and 21 b , it is also possible to use a configuration where one part of the outer circumference of the top end 100 a (the portion indicated by the broken line in FIG. 8 ) is not cut away.

Also, although an example where the clamp sensor 2 detects a magnetic field as the detected value and the processor 33 measures the current as the measured value is described above, the detected value and/or the measured value are not limited to a magnetic field and current and instead include various physical quantities such as voltage, power, and resistance.

It is also possible to use a clamp meter 1 A including a clamp sensor 2 A and the main body 3 depicted in FIG. 13 . Note that in the following description, component elements that are the same as the clamp sensor 2 and the clamp meter 1 described above have been assigned the same reference numerals and duplicated description is omitted.

In this clamp sensor 2 A, the front end portions 51 a and 51 b and the base end portions 52 a and 52 b are defined as follows. First, as depicted in FIG. 13 , a straight line H 2 that passes the top end 100 a of the ring-shaped body 100 and a centroid C 2 in plan view (the obliquely shaded shape in FIG. 13 ) of the inner circumference of the ring-shaped body 100 is defined. Next, a length L 101 A equivalent to 40% of a distance D 101 A (the straight line distance) from the top end 100 a (in more detail, the outer facing surface 101 at the top end 100 a depicted in FIG. 8 ) to the centroid C 2 is specified, and any point (hereinafter, also referred to the “defined point P 101 A”) is defined on the straight line H 2 in a range that is centered on the centroid C 2 and has the length L 101 A. Here, in this example, a point separated from the centroid C 2 toward the top end 100 a by a length corresponding to 14% of the distance D 101 is defined as the “defined point P 101 A”. After this, a plane that passes through the defined point P 101 A and is perpendicular to the straight line H 2 is defined as a “boundary plane Sb 2 ”, the parts between the boundary plane Sb 2 and the front ends 21 a and 21 b of the clamp arms 11 a and 11 b are defined as the “front end portions 51 a and 51 b ” and the parts between the boundary plane Sb 1 and the base ends 22 a and 22 b are defined as the “base end portions 52 a and 52 b”.

In this clamp sensor 2 A, as depicted in FIG. 7 , the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed in the same shape as the equivalent portions of the clamp sensor 2 . Also in this clamp sensor 2 A, as depicted in FIG. 6 , the clamp arms 11 a and 11 b are formed so that the area Sa 1 of the outer form of the section Sc 1 at the front end portions 51 a and 51 b is smaller than the area Sa 2 of the outer form of the section Sc 2 at the base end portions 52 a and 52 b . This means that with the clamp sensor 2 A, in the same way as the clamp sensor 2 , it is possible to easily insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b deeply into the narrow gaps G 1 and G 2 between adjacent conductors 400 without reducing the strength of the clamp arms 11 a and 11 b . Accordingly, the conductor 400 can be reliably clamped using the clamp sensor 2 .

With this clamp sensor 2 A also, as depicted in FIG. 8 , the clamp arms 11 a and 11 b are formed so that the length L 103 along the straight line H 1 between the outer facing surface 101 of the ring-shaped body 100 and the position P that is 15 mm from the center of the top end 100 a along a direction that is perpendicular to the straight line H 1 and parallel to the plane of the opening F in the ring-shaped body 100 is within the range of at least 9 mm but no greater than 11 mm. This means that in the same way as the clamp sensor 2 , the clamp sensor 2 A is capable of reliably clamping the conductor 400 while favorably maintaining favorable detection characteristics for magnetic fields.

In this clamp sensor 2 A also, as depicted in FIG. 9 , the clamp arms 11 a and 11 b are formed so that when the longest distance out of straight line distances between any two points on the outer form of the section Sc 1 at the front end portions 51 a and 51 b is set as the opposing distance D 1 (see FIG. 7 ) and a distance between the front ends 21 a and 21 b of the clamp arms 11 a and 11 b in a state where the front ends 21 a and 21 b are separated by the maximum amount is set as the separation distance D 102 , the ratio R of the opposing distance D 1 to the separation distance D 102 is within the range of at least 1/6 but no greater than 1/5. This means that with the clamp sensor 2 A, in the same way as the clamp sensor 2 , the front ends 21 a and 21 b can be easily inserted into the narrow gaps G 1 and G 2 between the adjacent conductors 400 in a state where the lever 30 a has been pressed in by the maximum amount. It is therefore possible to more reliably clamp only one out of the plurality of conductors 400 while sufficiently improving the operability.

It is also possible to use a clamp sensor 202 depicted in FIG. 7 . In this clamp sensor 202 , in the same way as the clamp sensor 2 described above, the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b include a pair of facing surfaces 101 , a pair of facing surfaces 102 , a pair of facing surfaces 103 , and a pair of facing surfaces 104 , so that as depicted in FIG. 7 , the outer form of the section Sc 1 that is perpendicular to the length direction of the clamp arms 11 a and 11 b is formed in an octagonal shape (one example of a substantially octagonal shape) as one example (that is, the front end portions 51 a and 51 b are octagonal pillars where the corners of a rectangular pillar depicted by the broken lines in FIG. 7 have been chamfered).

Also, in this clamp sensor 202 , as depicted in FIG. 5 , in the same way as the clamp sensor 2 described above, parts between the front ends 21 a and 21 b and the boundary plane Sb 1 , which is perpendicular to the straight line H 1 and passes the defined point P 101 (defined on the straight line H 1 in the range that is centered on the centroid C 1 and has the length L 101 ), are defined as the front end portions 51 a and 51 b , and parts between the boundary plane Sb 1 and the base ends 22 a and 22 b are defined as the base end portions 52 a and 52 b . Note that as depicted in FIG. 13 , in the same way as the clamp sensor 2 A described above, it is also possible to use a configuration where parts between the front ends 21 a and 21 b and the boundary plane Sb 2 that is perpendicular to the straight line H 2 and passes the defined point P 101 A (defined on the straight line H 2 in the range that is centered on the centroid C 2 and has the length L 101 A) are defined as the front end portions 51 a and 51 b and parts between the boundary plane Sb 2 and the base ends 22 a and 22 b are defined as the base end portions 52 a and 52 b.

Also, in the clamp sensor 202 , as depicted in FIG. 7 , parts of the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b aside from the front ends 21 a and 21 b are formed so that out of the edges of the octagon that is the outer form of the section Sc 1 , edges E 1 that correspond to the facing surfaces 101 and edges E 2 that correspond to the facing surfaces 102 have the same length L 1 and edges E 3 that correspond to the facing surfaces 103 and edges E 4 that correspond to the facing surfaces 104 have the same length L 2 . Also, in the clamp sensor 202 , the front end portions 51 a and 51 b are formed so that the opposing distance D 1 between the edges E 1 and the opposing distance D 2 between the edges E 2 are the same distance and the opposing distance D 3 between the edges E 3 (the opposing distance between a segment that joins both ends of one edge E 3 and a segment that joins both ends of the other edge E 3 ) and the opposing distance D 4 between the edges E 4 (the opposing distance between a segment that joins both ends of one edge E 4 and a segment that joins both ends of the other edge E 4 ) are the same distance. In addition, in the clamp sensor 202 , the front end portions 51 a and 51 b are formed so that the opposing distances D 3 and D 4 are within the range of over ( 100 /√2)% but no greater than 110% (as one example, 99%) of the opposing distances D 1 and D 2 (that is, the shorter distance out of the opposing distances D 1 and D 2 ).

Here, in a configuration in which the opposing distances D 3 and D 4 are ( 100 /√2)% or less of the opposing distances D 1 and D 2 , the shape of the section Sc 1 becomes thin (a shape that is vertically or horizontally elongated), and since the cores 41 also become thin due to this, there is the risk of deterioration in the magnetic characteristics and a fall in detection accuracy for the detected value. On the other hand, in a configuration where the opposing distances D 3 and D 4 are longer than 110% of the opposing distances D 1 and D 2 , it is difficult to sufficiently achieve the effects, described later, produced by shortening the opposing distances D 3 and D 4 . Accordingly, to sufficiently achieve the effects of shortening the opposing distances D 3 , D 4 while keeping the detection accuracy for the detected value high, this clamp sensor 202 uses a configuration where the opposing distances D 3 and D 4 are set within the range of over ( 100 /√2)% but no greater than 110% of the opposing distances D 1 and D 2 .

Note that in the example depicted in FIG. 7 , since the edges E 3 are both straight, the opposing distance between a segment that joins both ends of one of the edges E 3 and a segment that joins both ends of the other edge E 3 and the opposing distance between the edges E 3 themselves are the same. However, it is also possible to use a configuration where the edges E 3 are curved (arc-shaped) (a configuration where the outer form of the section Sc 1 is substantially octagonal), and with this configuration, the front end portions 51 a and 51 b are formed so that an opposing distance between a segment that joins both ends of one of the edges E 3 and a segment that joins both ends of the other edge E 3 is set as the opposing distance D 3 and this opposing distance D 3 is within the range of over ( 100 /√2)% but no greater than 110% of the opposing distances D 1 and D 2 . In the same way, in the example depicted in FIG. 7 , since the edges E 4 are both straight, the opposing distance between a segment that joins both ends of one of the edges E 4 and a segment that joins both ends of the other edge E 4 and the opposing distance between the edges E 4 themselves are the same. However, it is also possible to use a configuration where the edges E 4 are curved (arc-shaped) (a configuration where the outer form of the section Sc 1 is substantially octagonal), and with this configuration, the front end portions 51 a and 51 b are formed so that an opposing distance between a segment that joins both ends of one of the edges E 4 and a segment that joins both ends of the other edge E 4 is set as the opposing distance D 4 and this opposing distance D 4 is in the range of over ( 100 /√2)% but no greater than 110% of the opposing distances D 1 and D 2 .

In the clamp sensor 202 also, as depicted in FIG. 7 , the sensor cases 10 a and 10 b that construct the outer shells of the clamp arms 11 a and 11 b are formed so that the thickness T of parts corresponding to the front end portions 51 a and 51 b (hereinafter, referred to as the “front end parts of the sensor cases 10 a and 10 b ”) is uniform (or substantially uniform) when viewed at the section Sc 1 .

In the clamp sensor 202 also, as depicted in FIG. 6 , the clamp arms 11 a and 11 b are formed so that the base end portions 52 a and 52 b of the clamp arms 11 a and 11 b are substantially rectangular in cross-section and the area Sa 2 of the outer form of the section Sc 2 at the base end portions 52 a and 52 b are larger than the area Sa 1 of the outer form of the section Sc 1 at the front end portions 51 a and 51 b (that is, so that the area Sa 1 is smaller than the area Sa 2 ).

In this clamp sensor 202 also, as depicted in FIG. 8 , the facing surfaces 101 that construct the outer circumference surface of the ring-shaped body 100 at the front ends 21 a and 21 b of the clamp arms 11 a and 11 b are formed so as to produce a single flat surface that is perpendicular to a direction that connects the top end 100 a and the base end 100 b of the ring-shaped body 100 in a state where the ring-shaped body 100 is formed. By forming the facing surfaces 101 in this way, in the clamp sensor 202 , the clamp arms 11 a and 11 b are formed so that the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b is shorter than the opposing distance D 1 b between the facing surfaces 101 at other parts of the clamp arms 11 a and 11 b aside from the front ends 21 a and 21 b . This means that according to the clamp sensor 202 , the length of the ring-shaped body 100 along the direction that joins the top end 100 a and the base end 100 b is reduced by the reduction in the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b.

Here, as depicted by the broken lines in FIG. 7 , with the conventional configuration where the outer form of the section Sc 1 at each of the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b is rectangular (that is, a configuration where the corners of a rectangular pillar are not chamfered), the distance (the diagonal distance D 5 depicted in FIG. 7 ) between opposing corners of the rectangle that is the outer form of the section Sc 1 is around 141% of the opposing distance D 1 between the edges E 1 and the opposing distance D 2 between the edges E 2 (when the section Sc 1 is square). This means that with the conventional configuration, when the gap G 1 between the conductors 400 a and 400 b and the gap G 2 between the conductors 400 a and 400 c are narrow as depicted in FIG. 11 , it is difficult to insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the respective gaps G 1 and G 2 when the clamp meter 1 is tilted.

On the other hand, with the clamp sensor 202 and the clamp meter 1 equipped with the clamp sensor 202 , as described above, the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed so that out of the edges that construct the outer form of the section Sc 1 (in this example, an octagonal or substantially octagonal shape), the opposing distance D 3 between the edges E 3 (or the opposing distance D 3 between a segment that joins both ends of one edge E 3 and a segment that joins both ends of the other edge E 3 ) and the opposing distance D 4 between the edges E 4 (or the opposing distance D 4 between a segment that joins both ends of one edge E 4 and a segment that joins both ends of the other edge E 4 ) are within the range of over ( 100 /√2)% but no greater than 110% of the opposing distance D 1 between the edges E 1 and the opposing distance D 2 between the edges E 2 . This means that with the clamp sensor 202 and the clamp meter 1 , the opposing distances D 3 and D 4 can be made sufficiently shorter than the diagonal distance D 5 of the section Sc 1 in the conventional configuration, so that compared to the conventional configuration, the front ends 21 a and 21 b of the clamp arms 11 a and 11 b can be easily inserted into the narrow gaps G 1 and G 2 (see FIGS. 10 to 12 ) in a state where the clamp meter 1 is tilted. Accordingly, with the clamp sensor 202 and the clamp meter 1 , the conductor 400 that is the clamped object can be reliably clamped, even when another conductor 400 or an obstacle is present in the vicinity of the conductor 400 that is the clamped object.

Also, according to the clamp sensor 202 and the clamp meter 1 , by forming the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b so that both the opposing distances D 3 and D 4 (or both the opposing distance D 3 between a segment that joins both ends of one of the edges E 3 and a segment that joins both ends of the other edge E 3 and the opposing distance D 4 between a segment that joins both ends of one of the edges E 4 and a segment that joins both ends of the other edge E 4 ) are within the range of over ( 100 /√2)% but no greater than 110% of the opposing distances D 2 and D 3 , it is possible to make both the opposing distances D 3 and D 4 sufficiently shorter than the diagonal distance D 5 of the section Sc 1 in the conventional configuration. This means that according to the clamp sensor 202 and the clamp meter 1 , the front ends 21 a and 21 b of the clamp arms 11 a and 11 b can be easily inserted into the narrow gaps G 1 , G 2 , even in a state where for example the clamp meter 1 is tilted so as to rotate in either the clockwise or counterclockwise direction with the length direction of the clamp meter 1 as the rotational axis.

Also, in the clamp sensor 202 and the clamp meter 1 , since the clamp arms 11 a and 11 b are formed so that the thickness T of the front end parts of the sensor cases 10 a and 10 b that construct the outer shells of the clamp arms 11 a and 11 b is uniform (or substantially uniform) when viewed at the section Sc 1 , compared to a configuration where the thickness T of the front end parts of the sensor cases 10 a and 10 b is non-uniform, it is possible to avoid concentration of stress in parts of the sensor cases 10 a and 10 b where the thickness is low and to increase the strength of the sensor cases 10 a and 10 b . It is therefore possible to reliably avoid damage to the sensor cases 10 a and 10 b when a load is applied to the sensor cases 10 a and 10 b.

In the clamp sensor 202 and the clamp meter 1 also, by forming the clamp arms 11 a and 11 b so that the area of the section Sc 2 at the base end portions 52 a and 52 b is larger than the area of the section Sc 1 at the front end portions 51 a and 51 b , compared to a configuration where the clamp arms 11 a and 11 b are formed so that the area of the section Sc 1 at the front end portions 51 a and 51 b and the area of the section Sc 2 at the base end portions 52 a and 52 b are the same, it is possible to sufficiently increase the strength of the clamp arms 11 a and 11 b.

In this clamp sensor 202 also, as described above, the clamp arms 11 a and 11 b are formed so that the area Sa 1 of the outer form of the section Sc 1 at the front end portions 51 a and 51 b is smaller than the area Sa 2 of the outer form of the section Sc 2 at the base end portions 52 a and 52 b (see FIG. 6 ). This means that according to the clamp sensor 202 , in the same way as the clamp sensor 2 , it is possible to easily insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b deeply into the narrow gaps G 1 and G 2 between the adjacent conductors 400 without reducing the strength of the clamp arms 11 a and 11 b . Accordingly, it is possible to reliably clamp the conductor 400 using the clamp sensor 202 .

With the clamp sensor 202 also, as depicted in FIG. 8 , the clamp arms 11 a and 11 b are formed so that the length L 103 along the straight line H 1 between the outer facing surface 101 of the ring-shaped body 100 and the position P that is 15 mm from the center of the top end 100 a along a direction that is perpendicular to the straight line H 1 and parallel to the plane of the opening F in the ring-shaped body 100 is within the range of at least 9 mm but no greater than 11 mm. This means that according to the clamp sensor 202 , in the same way as the clamp sensor 2 , it is possible to reliably clamp the conductor 400 while maintaining favorable detection characteristics for magnetic fields.

In the clamp sensor 202 also, as depicted in FIG. 9 , the clamp arms 11 a and 11 b are formed so that when the longest distance out of straight line distances between any two points on the outer form of the section Sc 1 at the front end portions 51 a and 51 b is set as the opposing distance D 1 (see FIG. 7 ) and a distance between the front ends 21 a and 21 b of the clamp arms 11 a and 11 b in a state where the front ends 21 a and 21 b are separated by the maximum amount is set as the separation distance D 102 , the ratio R of the opposing distance D 1 to the separation distance D 102 is within the range of at least 1/6 but no greater than 1/5. This means that according to the clamp sensor 202 , in the same way as the clamp sensor 2 , it is possible to easily insert the front ends 21 a and 21 b into the narrow gaps G 1 and G 2 between the adjacent conductors 400 in a state where the lever 30 a is pressed in by the maximum amount. This means that it is possible to clamp one out of a plurality of conductors 400 even more reliably while sufficiently improving operability.

With the clamp sensor 202 and the clamp meter 1 also, by forming the clamp arms 11 a and 11 b so that the facing surfaces 101 on the outer circumferential sides of the front ends 21 a and 21 b of the clamp arms 11 a and 11 b are formed so as to produce a single flat surface that is perpendicular to a direction that connects the top end 100 a and the base end 100 b of the ring-shaped body 100 in the state where the ring-shaped body 100 is formed and the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b is shorter than the opposing distance D 1 b between the facing surfaces 101 at other parts of the clamp arms 11 a and 11 b aside from the front ends 21 a and 21 b , it is possible to insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the narrow gaps G 1 and G 2 even more easily. Since the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b is short, even when for example an obstacle such as a wall is present behind the conductor 400 that is the clamped object and the gap between the conductor 400 and the obstacle is narrow, it is still possible to reliably clamp the conductor 400 that is the clamped object while avoiding contact between the obstacle and the clamp arms 11 a and 11 b.

Note that with this clamp sensor 202 also, it is possible to use a configuration where the base end portions 52 a and 52 b of the clamp arms 11 a and 11 b are formed in the same shape as the front end portions 51 a and 51 b . It is also possible for the clamp sensor 202 to use a configuration where the edges E 1 and E 2 of the octagon, which is the outer form of the section Sc 1 , have different lengths and/or the edges E 3 and E 4 have different lengths. With the clamp sensor 202 , it is possible to use a configuration in which the opposing distances D 1 and D 2 are different lengths and the opposing distances D 3 and D 4 are different lengths. It is also possible for the clamp sensor 202 to use a configuration where the front end portions 51 a and 51 b are formed so that only one of the opposing distances D 3 and D 4 is within the range of over ( 100 /√2)% but no greater than 110% of the opposing distances D 1 and D 2 (that is, the shorter distance out of the opposing distance D 1 and D 2 ). In the clamp sensor 202 also, it is possible to use a configuration where both the front end portions 51 a and 51 b and the base end portions 52 a and 52 b of the clamp arms 11 a and 11 b are formed so that the edges E 3 and E 4 are curved (arc-shaped). With the clamp sensor 202 also, it is also possible to use a configuration where one part on the outer circumference of the top end 100 a of the ring-shaped body 100 (the portion indicated by the broken line in FIG. 8 ) is not cut away.

It is also possible to use a clamp sensor 302 depicted in FIG. 7 . In the same way as the clamp sensor 2 described above, in the clamp sensor 302 , the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b include a pair of facing surfaces 101 , a pair of facing surfaces 102 , a pair of facing surfaces 103 , and a pair of facing surfaces 104 , and as depicted in FIG. 7 , the outer form of the section Sc 1 that is perpendicular to the length direction of the clamp arms 11 a and 11 b is octagonal or substantially octagonal, for example (an octagonal pillar where the corners of a rectangular pillar depicted by the broken line in FIG. 7 have been chamfered).

In the clamp sensor 302 , as depicted in FIG. 5 , in the same way as the clamp sensor 2 described above, parts between the front ends 21 a and 21 b and the boundary plane Sb 1 , which is perpendicular to the straight line H 1 and passes the defined point P 101 (defined on the straight line H 1 in the range that is centered on the centroid C 1 and has the length L 101 ), are defined as the front end portions 51 a and 51 b , and parts between the base ends 22 a and 22 b and the boundary plane Sb 1 are defined as the base end portions 52 a and 52 b . Note that as depicted in FIG. 13 , in the same way as the clamp sensor 2 A described above, it is also possible to use a configuration where parts between the front ends 21 a and 21 b and the boundary plane Sb 2 that is perpendicular to the straight line H 2 and passes the defined point P 101 A (defined on the straight line H 2 in the range that is centered on the centroid C 2 and has the length L 101 A) are defined as the front end portions 51 a and 51 b and parts between the boundary plane Sb 2 and the base ends 22 a and 22 b are defined as the base end portions 52 a and 52 b.

With this clamp sensor 302 , as depicted in FIG. 7 , parts of the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b aside from the front ends 21 a and 21 b are formed so that out of the edges of the octagon that is the outer form of the section Sc 1 , the edges E 1 that correspond to the facing surfaces 101 and the edges E 2 that correspond to the facing surfaces 102 have the same length L 1 and the edges E 3 that correspond to the facing surfaces 103 and the edges E 4 that correspond to the facing surfaces 104 have the same length L 2 . Also, in the clamp sensor 302 , the front end portions 51 a and 51 b are formed so that the length L 2 of the edges E 3 and E 4 is within a range of at least 57% but less than 1000% (as one example, 106%) of the length L 1 of the edges E 1 and E 2 (that is, the shortest length out of the lengths of the edges E 1 and E 2 ).

Here, in a configuration where the length L 2 is 1000% or more of the length L 1 , the shape of the section Sc 1 becomes thin (a shape that is vertically or horizontally elongated), and since the cores 41 also become thin due to this, there is the risk of deterioration in the magnetic characteristics and a fall in the detection accuracy for the detected value. On the other hand, in a configuration where the length L 2 is below 57% of the length L 1 , it is difficult to sufficiently achieve the effects, described later, produced by chamfering the corners of a rectangular pillar and somewhat increasing the length L 2 . Accordingly, in the clamp sensor 2 , to sufficiently achieve the effects of somewhat increasing the length L 2 while keeping the detection accuracy for the detected value high, a configuration where the length L 2 is within the range of at least 57% but less than 1000% of the length L 1 is used.

Note that in the example depicted in FIG. 7 , since the edges E 3 and E 4 are both straight, the lengths of the segments that join both ends of the edges E 3 and E 4 are the same as the edges E 3 and E 4 . However, it is also possible to use a configuration where the edges E 3 and E 4 are curved (arc-shaped) (a configuration where the outer form of the section Sc 1 is substantially octagonal), and for this configuration, the length of a segment that joins both ends of the edges E 3 and E 4 is treated as the length L 2 and the front end portions 51 a and 51 b are formed so that the length L 2 is within the range of at least 57% but less than 1000% of the length L 1 (the shortest length out of the lengths of the edges E 1 and E 2 ).

In the clamp sensor 302 also, as depicted in FIG. 7 , the sensor cases 10 a and 10 b that construct the outer shells of the clamp arms 11 a and 11 b are formed so that the thickness T of parts corresponding to the front end portions 51 a and 51 b (hereinafter, referred to as the “front end parts of the sensor cases 10 a and 10 b ”) is uniform (or substantially uniform) when viewed at the section Sc 1 .

In the clamp sensor 302 also, the clamp arms 11 a and 11 b are formed so that the base end portions 52 a and 52 b of the clamp arms 11 a and 11 b are formed so as to be substantially rectangular in cross-section and the area of the section Sc 2 at the base end portions 52 a and 52 b is larger than the area of the section Sc 1 at the front end portions 51 a and 51 b (that is, so that the area Sa 1 is smaller than the area Sa 2 ).

In this clamp sensor 302 also, as depicted in FIG. 8 , the facing surfaces 101 that construct the outer circumferential surface of the ring-shaped body 100 at the front ends 21 a and 21 b of the clamp arms 11 a and 11 b are formed so as to produce a single flat surface that is perpendicular to a direction that connects the top end 100 a and the base end 100 b of the ring-shaped body 100 in a state where the ring-shaped body 100 is formed. By forming the facing surfaces 101 in this way, in the clamp sensor 302 , the clamp arms 11 a and 11 b are formed so that the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b is shorter than the opposing distance D 1 b between the facing surfaces 101 at other parts of the clamp arms 11 a and 11 b aside from the front ends 21 a and 21 b . This means that according to the clamp sensor 302 , the length of the ring-shaped body 100 along the direction that connects the top end 100 a and the base end 100 b is shorter by the reduction in the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b.

Here, as depicted by the broken lines in FIG. 7 , with the conventional configuration where the outer form of the section Sc 1 at each of the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b is rectangular (that is, a configuration where the corners of a rectangular pillar are not chamfered), the distance (the diagonal distance D 5 depicted in FIG. 7 ) between opposing corners of the rectangle that is the outer form of the section Sc 1 is longer than the opposing distance D 1 between the edges E 1 and the opposing distance D 2 between the edges E 2 . This means that with the conventional configuration, when the gap G 1 between the conductors 400 a and 400 b and the gap G 2 between the conductors 400 a and 400 c are narrow as depicted in FIG. 11 , it is difficult to insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the respective gaps G 1 and G 2 when the clamp meter 1 is tilted.

On the other hand, with the clamp sensor 302 and a clamp meter 1 equipped with the clamp sensor 302 , as described above, the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed so that the length L 2 of the edges E 3 and E 4 (or the length L 2 of segments that join both ends of the edges E 3 and E 4 ) out of the edges that construct the outer form (in this example, octagonal or substantially octagonal) of the section Sc 1 where the corners of a rectangular pillar have been chamfered is within the range of at least 57% but less than 1000% of the length L 1 of the edges E 1 and E 2 . This means that according to the clamp sensor 302 and the clamp meter 1 , by somewhat increasing the length L 2 , the opposing distances D 3 and D 4 are sufficiently shorter than the diagonal distance D 5 of the section Sc 1 in the conventional configuration, so that compared to the conventional configuration, it is possible to easily insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the narrow gaps G 1 and G 2 (see FIGS. 10 to 12 ) in a state where the clamp meter 1 is tilted. Accordingly, with the clamp sensor 302 and the clamp meter 1 , even if another conductor 400 or an obstacle is present in the vicinity of the conductor 400 that is the clamped object, it is still possible to reliably clamp the conductor 400 that is the clamped object.

Also, with the clamp sensor 302 and the clamp meter 1 , by forming the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b so that the length L 2 of every edge E 3 and E 4 (or the length L 2 of every segment that joins both ends of the edges E 3 and E 4 ) is within the range of at least 57% but less than 1000% of the length L 1 of the edges E 1 and E 2 , it is possible to make both of the opposing distances D 3 and D 4 sufficiently shorter than the diagonal distance D 5 of the section Sc 1 in the conventional configuration. This means that according to the clamp sensor 302 and the clamp meter 1 , the front ends 21 a and 21 b of the clamp arms 11 a and 11 b can be easily inserted into the narrow gaps G 1 and G 2 , even when for example the clamp meter 1 is tilted so as to rotate in either the clockwise or counterclockwise direction with the length direction of the clamp meter 1 as the rotational axis.

Also, with the clamp sensor 302 and the clamp meter 1 , since the clamp arms 11 a and 11 b are formed so that the thickness T of the front end parts of the sensor cases 10 a and 10 b that construct the outer shells of the clamp arms 11 a and 11 b is uniform (or substantially uniform) when viewed at the section Sc 1 , compared to a configuration where the thickness T of the front end parts of the sensor cases 10 a and 10 b is non-uniform, it is possible to avoid concentration of stress in parts of the sensor cases 10 a and 10 b where the thickness T is low and to increase the strength of the sensor cases 10 a and 10 b . It is therefore possible to reliably avoid damage to the sensor cases 10 a and 10 b when a load is applied to the sensor cases 10 a and 10 b.

Also, with the clamp sensor 302 and the clamp meter 1 , by forming the clamp arms 11 a and 11 b so that the area of the section Sc 2 at the base end portions 52 a and 52 b is larger than the area of the section Sc 1 at the front end portions 51 a and 51 b , compared to a configuration where the clamp arms 11 a and 11 b are formed so that the area of the section Sc 1 at the front end portions 51 a and 51 b and the area of the section Sc 2 at the base end portions 52 a and 52 b are the same, it is possible to sufficiently increase the strength of the clamp arms 11 a and 11 b.

With this clamp sensor 302 also, as described above, the clamp arms 11 a and 11 b are formed so that the area Sa 1 of the outer form of the section Sc 1 at the front end portions 51 a and 51 b is smaller than the area Sa 2 of the outer form of the section Sc 2 at the base end portions 52 a and 52 b (see FIG. 6 ). This means that according to the clamp sensor 302 , in the same way as the clamp sensor 2 , it is possible to easily insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b deeply into the narrow gaps G 1 and G 2 between adjacent conductors 400 without reducing the strength of the clamp arms 11 a and 11 b . Accordingly, it is possible to reliably clamp the conductor 400 using the clamp sensor 302 .

In the clamp sensor 302 also, as depicted in FIG. 8 , the clamp arms 11 a and 11 b are formed so that the length L 103 along the straight line H 1 between the outer facing surface 101 of the ring-shaped body 100 and the position P that is 15 mm from the center of the top end 100 a along a direction that is perpendicular to the straight line H 1 and parallel to the plane of the opening F in the ring-shaped body 100 is within the range of at least 9 mm but no greater than 11 mm. This means that according to the clamp sensor 302 , in the same way as the clamp sensor 2 , it is possible to reliably clamp the conductor 400 while maintaining favorable detection characteristics for magnetic fields.

Also, with the clamp sensor 302 , as depicted in FIG. 9 , the clamp arms 11 a and 11 b are formed so that when the longest distance out of straight line distances between any two points on the outer form of the section Sc 1 at the front end portions 51 a and 51 b is set as the opposing distance D 1 (see FIG. 7 ) and a distance between the front ends 21 a and 21 b of the clamp arms 11 a and 11 b in a state where the front ends 21 a and 21 b are separated by the maximum amount is set as the separation distance D 102 , the ratio R of the opposing distance D 1 to the separation distance D 102 is within the range of at least 1/6 but no greater than 1/5. This means that according to the clamp sensor 302 , in the same way as the clamp sensor 2 , it is possible to easily insert the front ends 21 a and 21 b into the narrow gaps G 1 and G 2 between the adjacent conductors 400 in a state where the lever 30 a is pressed in by the maximum amount. This means that it is possible to clamp one out of a plurality of conductors 400 even more reliably while sufficiently improving operability.

With the clamp sensor 302 and the clamp meter 1 also, by forming the clamp arms 11 a and 11 b so that the facing surfaces 101 on the outer circumferential sides of the front ends 21 a and 21 b of the clamp arms 11 a and 11 b are formed so as to produce a single flat surface that is perpendicular to a direction that connects the top end 100 a and the base end 100 b of the ring-shaped body 100 in the state where the ring-shaped body 100 is formed and the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b is shorter than the opposing distance D 1 b between the facing surfaces 101 at other parts of the clamp arms 11 a and 11 b aside from the front ends 21 a and 21 b , it is possible to insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b even more easily into the narrow gaps G 1 and G 2 . Since the opposing distance D 1 a between the facing surfaces 101 at the front ends 21 a and 21 b is short, even when for example an obstacle such as a wall is present behind the conductor 400 that is the clamped object and the gap between the conductor 400 and the obstacle is narrow, it is still possible to reliably clamp the conductor 400 that is the clamped object while avoiding contact between the obstacle and the clamp arms 11 a and 11 b.

Note that with this clamp sensor 302 also, it is possible to use a configuration where the base end portions 52 a and 52 b of the clamp arms 11 a and 11 b are formed in the same shape as the front end portions 51 a and 51 b . It is also possible for the clamp sensor 302 to use a configuration where the edges E 1 and E 2 of the octagon, which is the outer form of the section Sc 1 , have different lengths, and/or where the edges E 3 and E 4 have different lengths. Also, with the clamp sensor 302 , so long as a condition that at least one length of the edges E 3 and E 4 is in the range of at least 57% but less than 1000% of the shortest length out of the lengths of the edges E 1 and E 2 , it is possible to set the edges E 1 , E 2 , E 3 , and E 4 at arbitrary lengths. With the clamp sensor 302 also, it is possible to use a configuration where both the front end portions 51 a and 51 b and the base end portions 52 a and 52 b of the clamp arms 11 a and 11 b are formed so that the edges E 3 and E 4 are curved (arc-shaped). It is also possible for the clamp sensor 302 to use a configuration where one part of the outer circumference of the top end 100 a of the ring-shaped body (the portion indicated by the broken line in FIG. 8 ) is not cut away.

Although examples where the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed so that the outer form of the section Sc 1 at the front end portions 51 a and 51 b is substantially octagonal have been described above, it is also possible to form the front end portions 51 a and 51 b so that the outer form of the section Sc 1 is a polygonal shape aside from a substantially octagonal shape (as examples, a substantially 12-sided or 16-sided shape). As one example, it is possible to use the clamp sensor 402 depicted in FIG. 14 .

In this clamp sensor 402 , the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b have a pair of facing surfaces 101 that correspond to first facing surfaces, a pair of facing surfaces 102 that correspond to second facing surfaces, and a pair of facing surfaces 103 a , a pair of facing surfaces 103 b , a pair of facing surfaces 104 a , and a pair of facing surfaces 104 b (which all correspond to “third facing surfaces”, and are a total of four pairs of third facing surfaces as one example of a plurality of pairs) that are inclined with respect to the facing surfaces 101 and 102 , so that the outer form of the section Sc 1 that is perpendicular to the length direction of the clamp arms 11 a and 11 b is formed in a substantially 12-sided shape. Note that since the front end portions 51 a and 51 b have the same cross-sectional form, only the cross-sectional form of the front end portion 51 a is depicted in FIG. 14 and the cross-sectional form of the front end portion 51 b is omitted.

As depicted in FIG. 14 , in the clamp sensor 402 , parts of the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b aside from the front ends 21 a and 21 b are formed so that out of the edges of the 12-sided shape that is the outer form of the section Sc 1 , the edges E 1 that correspond to the facing surfaces 101 and the edges E 2 that correspond to the facing surfaces 102 are the same length L 1 , and the lengths of the edges E 3 a and E 3 b that correspond to the facing surfaces 103 a and 103 b (or lengths of segments that join both ends of the edges E 3 a and E 3 b ) and the edges E 4 a and E 4 b that correspond to the facing surfaces 104 a and 104 b (or lengths of segments that join both ends of the edges E 4 a and E 4 b ) are the same length L 2 . In addition, in the clamp sensor 402 , the front end portions 51 a and 51 b are formed so that the length L 2 is longer than the length L 1 (a shortest length out of the lengths of the edges E 1 and E 2 ).

With this clamp sensor 402 also, as depicted in FIG. 14 , the sensor cases 10 a and 10 b that construct the outer shells of the clamp arms 11 a and 11 b are formed so that the thickness T of the parts corresponding to the front end portions 51 a and 51 b (hereinafter, referred to as the “front end parts of the sensor cases 10 a and 10 b ”) is uniform (or substantially uniform) when viewed at the section Sc 1 . This means that according to the clamp sensor 402 , compared to a configuration where the thickness T of the front end parts of the sensor cases 10 a and 10 b is non-uniform, it is possible to avoid concentration of stress in parts of the sensor cases 10 a and 10 b where the thickness is low and to increase the strength of the sensor cases 10 a and 10 b . It is therefore possible to reliably avoid damage to the sensor cases 10 a and 10 b when a load is applied to the sensor cases 10 a and 10 b.

Note that in the clamp sensor 402 , as depicted in FIG. 14 , it is possible to form the front end portions 51 a and 51 b so that the opposing distance D 1 between the edges E 1 and the opposing distance D 2 between the edges E 2 in the 12-sided shape that is the outer form of the section Sc 1 are the same distance, the opposing distances D 3 a and D 3 b between the edges E 3 a and E 3 b (the opposing distance between a segment that joins both ends of one of the edges E 3 a and E 3 b and a segment that joins both ends of the other of the edges E 3 a and E 3 b ) and the opposing distances D 4 a and D 4 b between the edges E 4 a and E 4 b (the opposing distance between a segment that joins both ends of one of the edges E 4 a and E 4 b and a segment that joins both ends of the other of the edges E 4 a and E 4 b ) are the same distance, and the opposing distances D 3 a , D 3 b , D 4 a , and D 4 b are within a range of over ( 100 /√2)% but no greater than 110% (as one example, 99%) of the opposing distances D 1 and D 2 (the shorter of the opposing distances D 1 and D 2 ). In this case also, the effects described above can be achieved.

Also in the clamp sensor 402 , as depicted in FIG. 14 , it is possible to form the front end portions 51 a and 51 b so that the length L 2 of the edges E 3 a , E 3 b , E 4 a , and E 4 b in the 12-sided shape that is the outer form of the section Sc 1 is within a range of at least 57% but less than 1000% (as one example, 106%) of the length L 1 of the edges E 1 and E 2 (the shortest length out of the lengths of the edges E 1 and E 2 ). In this case also, the effects described above can be achieved.

Also, when there are three pairs or five or more pairs of third facing surfaces that are inclined with respect to the first facing surfaces and the second facing surfaces and the number of pairs of third facing surfaces is expressed as “n”, it is possible to use a configuration where the outer form of the section Sc 1 is a variety of polygonal shapes that are substantially (4+2n) sided shapes (where n is a natural number of 2 or higher). In this case also, the effects described above can be achieved.

It is also possible to use a configuration where the front end portions 51 a and 51 b are formed so that part of the outer form of the section Sc 1 is curved. As an example, the clamp sensor 502 depicted in FIG. 15 can be used. Note that since the front end portions 51 a and 51 b have the same cross-sectional form, only the cross-sectional form of the front end portion 51 a is depicted in FIG. 15 and the cross-sectional form of the front end portion 51 b is omitted.

As depicted in FIG. 15 , in the clamp sensor 502 , the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b have the pair of facing surfaces 101 (which correspond to first facing surfaces) that construct the outer circumferential surface and the inner circumferential surface of the ring-shaped body 100 and the pair of facing surfaces 102 (which correspond to second facing surfaces) that construct two side surfaces of the ring-shaped body 100 . The outer shape of the section Sc 1 that is perpendicular to the length direction of the clamp arms 11 a and 11 b is formed in a shape produced by cutting away both ends in the major axis of an oval along a direction perpendicular to the plane of the opening F in the ring-shaped body 100 (the left-right direction in FIG. 15 ). In this clamp sensor 502 , out of the edges that construct the outer form of the section Sc 1 , the edges E 1 that correspond to the facing surfaces 101 are formed so as to be straight and the edges E 2 that correspond to the facing surfaces 102 are formed so as to be arcs that are outwardly curved (a shape where the corners of a rectangular pillar depicted by the broken lines in FIG. 15 have been chamfered). In this clamp sensor 502 , the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed so that the longest opposing distance D 6 between the edges E 2 along the direction perpendicular to the plane of the opening F of the ring-shaped body 100 is no greater than the opposing distance D 1 between the edges E 1 . In this clamp sensor 502 , since the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed in this way, as depicted in FIG. 15 , the longest opposing distances D 7 and D 8 between the edges E 2 are no greater than the opposing distance D 1 between the edges E 1 . Note that in FIG. 15 , an example where the opposing distance D 1 and the opposing distances D 7 and D 8 are equal is depicted.

In the clamp sensor 502 , as depicted in FIG. 15 also, the sensor cases 10 a and 10 b that construct the outer shells of the clamp arms 11 a and 11 b are formed so that the thickness T of the parts corresponding to the front end portions 51 a and 51 b (hereinafter, referred to as the “front end parts of the sensor cases 10 a and 10 b ”) is uniform (or substantially uniform) when viewed at the section Sc 1 .

According to the clamp sensor 502 and a clamp meter 1 equipped with the clamp sensor 502 , by forming the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b so that out of the edges that construct the outer form of the section Sc 1 , the edges E 1 are straight and the edges E 2 are formed so as to be arcs that are outwardly curved, it is possible to make the longest opposing distances D 7 and D 8 between the edges E 2 no greater than the opposing distance D 1 between the edges E 1 . This means that compared to the conventional configuration (a configuration where the corners of a rectangular pillar are not chamfered) where the outer form of the section Sc 1 at the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b is rectangular and the diagonal distance D 5 of the section Sc 1 is longer than the opposing distance D 1 between the edges E 1 and the longest opposing distances D 7 and D 8 between the edges E 2 , it is possible to easily insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into narrow gaps G 1 and G 2 in a state where the clamp meter 1 is tilted. This means that according to the clamp sensor 502 and the clamp meter 1 , even when another conductor 400 or an obstacle is present in the vicinity of the conductor 400 that is the clamped object, it is possible to reliably clamp the conductor 400 that is the clamped object.

With the clamp sensor 502 and the clamp meter 1 equipped with the clamp sensor 502 , the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed so that the longest opposing distance D 6 between the edges E 2 along the direction perpendicular to the plane of the opening F of the ring-shaped body 100 is no greater than the opposing distance D 1 between the edges E 1 . This means that according to the clamp sensor 502 and the clamp meter 1 , by tilting the clamp meter 1 so as to reduce the angle of inclination of the plane of the opening F in the ring-shaped body 100 relative to the direction in which the conductor 400 extends, it is possible to insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the narrow gaps G 1 and G 2 even more easily.

Also, according to the clamp sensor 502 and the clamp meter 1 equipped with the clamp sensor 502 , by forming the clamp arms 11 a and 11 b so that the thickness T of the front end parts of the sensor cases 10 a and 10 b that construct the outer shells of the clamp arms 11 a and 11 b are uniform (or substantially uniform) when looking from the section Sc 1 , compared to a configuration where the thickness T of the front end parts of the sensor cases 10 a and 10 b is non-uniform, it is possible to avoid concentration of stress in parts of the sensor cases 10 a and 10 b where the thickness is low and to increase the strength of the sensor cases 10 a and 10 b . It is therefore possible to reliably avoid damage to the sensor cases 10 a and 10 b when a load is applied to the sensor cases 10 a and 10 b.

Also, as another example of a configuration where the front end portions 51 a and 51 b are formed so that part of the outer form of the section Sc 1 is formed by curves, it is also possible to use a clamp sensor 602 depicted in FIG. 16 . Note that since the cross-sectional form of the front end portions 51 a and 51 b is the same, only the cross-sectional form of the front end portion 51 a is illustrated in FIG. 16 and the cross-sectional form of the front end portion 51 b is omitted.

In the clamp sensor 602 , as depicted in FIG. 16 , the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b have a pair of facing surfaces 101 that construct the outer circumferential surface and the inner circumferential surface of the ring-shaped body 100 (and correspond to “first facing surfaces”), a pair of facing surfaces 102 that construct two side surfaces of the ring-shaped body 100 (and correspond to “second facing surfaces”), and two pairs of facing surfaces 105 that are positioned between the facing surfaces 101 and the facing surfaces 102 (and correspond to “fourth facing surfaces”). The outer form of the section Sc 1 that is perpendicular to the length direction of the clamp arms 11 a and 11 b is rectangular with rounded (curved) corners. In the clamp sensor 602 , out of the edges that construct the outer form of the section Sc 1 , the edges E 1 that correspond to the facing surfaces 101 and the edges E 2 that correspond to the facing surfaces 102 are straight and the edges E 5 that correspond to the facing surfaces 105 are arc-shaped so as to be outwardly curved (in a form where the corners of a rectangular pillar indicated by the broken lines in FIG. 16 are chamfered into curved surfaces). Also, with the clamp sensor 602 , the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed so that the opposing distance D 9 between the edges E 2 is no greater than the opposing distance D 1 between the edges E 1 . In this clamp sensor 602 , by forming the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b in this way, as depicted in FIG. 16 , the longest opposing distances D 10 and D 11 between the facing edges E 5 are no greater than the opposing distance D 1 between the edges E 1 . Note that in FIG. 16 , an example where the opposing distance D 1 and the opposing distances D 10 and D 11 are equal is depicted.

With the clamp sensor 602 also, as depicted in FIG. 16 , the sensor cases 10 a and 10 b that construct the outer shells of the clamp arms 11 a and 11 b are formed so that the thickness T of parts corresponding to the front end portions 51 a and 51 b (hereinafter, referred to as “front end parts of the sensor cases 10 a and 10 b ”) is uniform (or substantially uniform) when viewed at the section Sc 1 .

According to the clamp sensor 602 and a clamp meter 1 equipped with this clamp sensor 602 , by forming the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b so that out of the edges that construct the outer form of the section Sc 1 , the edges E 1 and the edges E 2 are straight and the edges E 5 are arc-shaped so as to be outwardly curved, it is possible to make the longest opposing distances D 10 and D 11 between the facing edges E 5 no greater than the opposing distance D 1 between the edges E 1 . This means that compared to a conventional configuration (a configuration where the corners of a rectangular pillar are not chamfered) where the outer form of the section Sc 1 at the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b is rectangular and the diagonal distance D 5 of the section Sc 1 is formed so as to be longer than the opposing distance D 1 between the edges E 1 and the opposing distance D 9 of the edges E 2 , it is possible to easily insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the narrow gaps G 1 and G 2 in a state where the clamp meter 1 is tilted. This means that according to the clamp sensor 602 and the clamp meter 1 , even when another conductor 400 or an obstacle is present in the vicinity of the conductor 400 that is the clamped object, it is possible to reliably clamp the conductor 400 that is the clamped object.

According to the clamp sensor 602 and the clamp meter 1 equipped with the clamp sensor 602 , the front end portions 51 a and 51 b of the clamp arms 11 a and 11 b are formed so that the opposing distance D 9 between the edges E 2 is no greater than the opposing distance D 1 between the edges E 1 . This means that according to the clamp sensor 602 and the clamp meter 1 , by tilting the clamp meter 1 so as to reduce the angle of inclination of the plane of the opening F in the ring-shaped body 100 relative to the direction in which the conductor 400 extends, it is possible to insert the front ends 21 a and 21 b of the clamp arms 11 a and 11 b into the narrow gaps G 1 and G 2 even more easily.

According to the clamp sensor 602 and the clamp meter 1 including the clamp sensor 602 , by forming the clamp arms 11 a and 11 b so that the thickness T of the front end parts of the sensor cases 10 a and 10 b that construct the outer shells of the clamp arms 11 a and 11 b is uniform (or substantially uniform) when viewed at the section Sc 1 , compared to a configuration where the thickness T of the front end parts of the sensor cases 10 a and 10 b is non-uniform, it is possible to avoid concentration of stress in parts of the sensor cases 10 a and 10 b where the thickness is low and to increase the strength of the sensor cases 10 a and 10 b . It is therefore possible to reliably avoid damage to the sensor cases 10 a and 10 b when a load is applied to the sensor cases 10 a and 10 b.

Although example configurations where the clamp arm 11 b (one of the clamp arms 11 a and 11 b ) is rotatable have been described above, it is also possible to use a configuration where the clamp arm 11 a is rotatable and a configuration where both the clamp arms 11 a and 11 b are rotatable.

According to the present invention, since it is possible to easily insert front ends of the clamp arms into narrow gaps in a state where a measuring device is tilted, even when for example another conductor or an obstacle is present in the vicinity of the conductor that is the clamped object, it is still possible to reliably clamp the conductor that is the clamped object. This means that the present invention can be widely applied to clamp sensors that detect a detected value for a clamped object and to measuring devices that measure a measured value for a clamped object.

1 Clamp meter

2 , 2 A, 202 , 302 , 402 , 502 , 602 Clamp sensor

11 a , 11 b Clamp arm

21 a , 21 b Front end

22 a , 22 b Base end

23 Rotational axis

33 Processor

41 Core

51 a , 51 b Front end portion

52 a , 52 b Base end portion

100 Ring-shaped body

100 a Top end

400 , 400 a Conductor

101 to 105 , 103 a , 103 b , 104 a , 104 b Facing surface

C 1 , C 2 Centroid

D 1 to D 11 Opposing distance

D 102 Separation distance

E 1 to E 5 , E 3 a , E 3 b , E 4 a , E 4 b Edge

H 1 , H 2 Straight line

L 1 , L 2 Length

L 101 , L 101 A, L 102 , L 103 Length

Mc Magnetic circuit

P Position

P 101 , P 101 A Defined point

Sa 1 , Sa 2 Area

Sb 1 , Sb 2 Boundary plane

Sc 1 , Sc 2 Section

T Thickness