Plug-in module for a liquid or gas sensor

The present invention relates to a plug-in module for a liquid or gas sensor

Liquid- or gas-sensors are used for measuring pH-value or redox potential, temperature, conductivity, or turbidity in liquids.

In the following, the discussion will essentially concern potentiometric sensors, as an example for a liquid- or gas-sensor.

Potentiometric sensors are mostly used for determining potentials in the case of high resistances, such as is the case with pH-measurements and redox measurements. With the help of pH-electrodes, or redox electrodes, the potentials of the solutions are registered.

In many applications, these electrodes are exposed to heavy wear, such that they frequently must be replaced after a short operating time.

There are very simply constructed pH-sensors, which are made up of only one pH-electrode without any other electronic components. These pH-electrodes deliver a pH-dependent potential, which can be tapped at suitable electrical connections. Optionally, for temperature compensation, these pH-electrodes have an integrated temperature sensor, e.g. PT100, the potential of which can be tapped at suitable temperature outputs. For measuring, these pH-sensors are normally connected via a cable to a transmitter, which generates a measurement signal from the pH-dependent potential and, if necessary, from the temperature signal of the temperature sensor.

Besides the simple pH-electrodes, or sensors, described, there are also such with integrated preamplifiers for impedance conversion. The output signal of the preamplifier is the potential of the pH-sensor, with, however, instead of the internal resistance of the pH-sensor, which lies in the order of magnitude of 100 MΩ, the internal resistance of the preamplifier of a few Ω now being determinative. Therefore, the further transfer and processing of the output potential is greatly simplified for a transmitter. The preamplifier is supplied with voltage either via a battery or via a cable.

Furthermore, simple transmitters, which are mounted directly on the pH-sensors, are available under the name “Direct Line” of the firm, Honeywell. These make it possible to generate, right at the sensor, e.g. a 4-20 mA measurement signal, which can then be transferred directly to a control station.

In the case of all known pH-electrodes, or pH-sensors, it is necessary to calibrate the electrodes after connection to the transmitter, in order to be able to store the ascertained calibration parameters in the transmitter. Sensor-specific information, such as the designation of the measuring point, etc., is normally not available on-site, that is, in the direct the vicinity of the sensor.

The sensor system offered by the firm, Endress+Hauser, under the mark, MEMOSENS, includes a sensor module and a sensor module head, which can be plugged together. Data exchange between sensor module and sensor module head, and energy supply to the sensor module, are accomplished inductively via a connecting section, which serves for galvanic decoupling. Furthermore, a sensor module is provided in the digital memory, in which, among other things, calibration parameters are stored. This technology is disclosed, for example, in the German (published applications) DE 100 55 090 and DE 102 18 606.

As an accessory to a sensor as disclosed therein, German Offenlegungsschrift DE 103 44 262 discloses a plug-in module, which especially enables sensor-specific information to be represented on-site, directly at the sensor, and furthermore enables a checking of the measurement values sent to the control station. In a special embodiment, this module is not only suited to display data from the sensor, but also to transfer such to a superordinated unit, per cable or per radio.

In certain applications, data transfer per radio requires an energy expenditure too large to allow sustained operation of the sensor by means of a plug-in module. On the other hand, operation of the sensor by means of a cable, which runs from a measuring transmitter to the sensor, is not always practical, especially in the case of remotely-positioned sensors.

Therefore, it is an object of the present invention to provide a sensor module head, especially one that can be plugged in, which overcomes the disadvantages of the state of the art.

This object is achieved by the provision of a sensor module head, for a liquid or gas sensor, which includes a sensor module and a sensor module head, which can be releasably connected together, and which, when connected, enable data and energy transfer via a galvanically decoupled transfer section, with the sensor module head having an energy supply unit for operating the sensor module head and the sensor module as well as a data memory, in order to store sensor data received from the sensor module.

In a further development of the invention, the sensor module head can have a display unit, which serves for displaying sensor data stored in the sensor module head.

For further processing or evaluation of the sensor data, the sensor module head can be detached, for example, from the sensor module, and connected to a suitable readout device for reading out the sensor data. The sensor data can include measurement data, whose course was logged over an extended period of time, or the data can concern condition data of the sensor module.

The galvanically decoupled transfer section includes, for example, an inductive transfer section with a primary-side inductive interface in the sensor head module, and a secondary-side inductive interface in the sensor module, with energy supply of the sensor module being accomplished via an AC signal, and wherein data transfer from the sensor module to the sensor head module can be realized by load modulation of the AC signal.

The readout of the sensor module head can be accomplished, for example, via the inductive interface, or an additional interface, provided if necessary.

The invention will now be described in greater detail on the basis of an example of an embodiment illustrated in the drawing, whose figures show as follows:

FIG. 1 schematic representation of a sensor module;

FIG. 2 schematic representation of a sensor module head;

FIG. 1 shows a sensor module SM in greater detail. Sensor module SM is composed of a measured value transducer MT (e.g. a glass electrode), which is submerged in the liquid to be measured. The measured value transducer supplies an analog measurement signal, which is pre-processed in an analog signal processing unit SP.

The processed analog measurement signal is then converted in the analog-digital converter A/D into a digital value, which is processed further in a microcontroller μC 1 . Microcontroller μC 1 is connected with a coil L 1 via a modem M/D and a power supply PS. The power supply PS provides the entire sensor module with voltage. A sensor module head, shown in greater detail in FIG. 2 , is formed such that it fits with the sensor module SM. Thus, the sensor module head SMH and the sensor module SM can be connected together by plugging one into the other. In the sensor module head SMH, a coil L 2 is connected with a modem M 2 via an amplifier A.

A data and energy exchange takes place via the coils L 1 and L 2 . Further details concerning inductive data exchange via ASK or FSK between the secondary-side sensor module and the primary-side sensor module head, and the energy supply of the sensor module via inductive coupling can be gathered from the above-named German published applications.

Additionally, sensor module head SMH has a microcontroller μC for controlling the components of the sensor module head, with the microcontroller including a data memory MEM, in which sensor data received from the sensor module can be stored. In addition, an energy, or power, supply unit ESU is provided for feeding the components of the sensor module head. The energy supply unit ESU can be a battery or solar cells in combination with an energy storer, for example an accumulator.

Sensor-specific information, such as e.g. measuring point designation, can be represented on an optionally-provided display D. For this, the corresponding data are read out directly from the sensor module SM or from the data memory MEM in the sensor module head.

For reading out the sensor data stored in the data memory MEM, and for programming the microcontroller, a suitable interface I/O is provided.

The application of a supply voltage for charging the ESU can also occur via the interface, for example, or a separate connection can be provided.