JPH01172743A - Sensor connection judging circuit for constant potential electrolysis type gas measuring apparatus - Google Patents

Abstract

PURPOSE: To enable monitoring of a connection state constantly without affecting a sensor itself by grounding either the operation electrode or the counter electrode of a constant potential electrolytic type sensor via a reactance coil. CONSTITUTION: When a target gas enters a sensor 1 in a state where a constant potential is being applied by a measurement circuit 3, an electrolytic current that is proportional to gas concentration flows between a counter electrode 2 and an operation electrode 4 so that the resistance of the sensor 1 changes in proportion with the gas concentration, thus measuring gas concentration. Pulses outputted from a pulse generator 6 are applied to the operation electrode 4 of the sensor 1 and a reactance coil 5. However, since the counter electrode 2 and the operation electrode 4 are arranged oppositely via an electrolyte in the sensor 1 and a capacitor is formed in terms of AC, pulses pass through the sensor 1 at a low impedance and flow to the ground via the circuit 3. As a result, the operation electrode 4 is placed in the state of being grounded for the pulses and voltages at a level that can be detected are generated between the terminals of the coil 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a circuit that determines whether or not a constant potential electrolytic gas sensor is connected to a measurement circuit.

(Prior art) A potentiostatic electrolytic gas sensor applies a constant potential between a working electrode and a counter electrode and detects the electrolytic current generated by the inflow of target gas, or detects the electrolytic current generated in the absence of target gas. has an extremely high impedance, so even if the sensor is detached from the measurement circuit, the indicator does not change, and there is a problem in that the detachment of the sensor is not noticed and measurement errors occur.

In order to solve these problems, the present applicant applied a pulsed transient voltage between the working electrode and the counter electrode of a potentiostatic electrolytic gas sensor, thereby reducing the electrochemical change between the counter electrode and the working electrode. We proposed a method for determining the quality of the connection based on S (Figure 6) based on the sensor output (Utokokai 56-14
Publication No. 2359).

According to this design, it is possible to reliably determine whether or not the sensor is connected to the measurement design, and the reliability of the gas measurement device can be improved. We were forced to wait for six guns, which usually takes about 30 seconds, to return to a steady state.
Therefore, there is an inconvenience that monitoring during the measurement period is impossible.

(Purpose) The present invention was made in view of the above problems, and its purpose is to provide a constant potential electrolytic gas measurement system that can constantly monitor the connection state without affecting the sensor itself. An object of the present invention is to provide a sensor connection determination circuit in a device.

(Summary of the Invention) That is, the present invention is characterized in that one of the working electrode or the counter electrode of a constant potential electrolytic gas sensor is grounded via an inductive reactance element, and a pulse signal is applied to the grounding side pole. is applied to determine the terminal voltage of the reactance element.

(Example) The details of the present invention will be described below based on illustrated examples.

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 is a two-electrode constant potential electrolytic gas sensor, and in this embodiment, the counter electrode 2 is connected to the sensor output measuring circuit 3, and As the working electrode 4 is grounded via the actuation coil 5 (described later), a constant voltage V is always applied from the measuring circuit 3. is applied to the gates of the counter electrode 2 and the working electrode 4 to detect changes in electrolytic current caused by the target gas. Reference numeral 5 denotes the above-mentioned reactance coil, and the connection point with the sensor 1, that is, the working electrode 4, is connected to the output terminal of a pulse generator 6 that generates a pulse with a time width of about 4 μsec, for example, without changing the electrolytic current. A potential detection circuit 7 is connected to detect the potential between the ground and the ground.

FIG. 4 shows an embodiment of the above-mentioned potential detection circuit, in which reference symbol Tl is a potential detection transistor;
An actance coil 5 is connected to the base electrode, the base electrode is connected to ground, and the collector electrode is connected to one end of a capacitor C for setting a time constant and the base electrode of an amplifying transistor T2.

Next, the operation of the apparatus configured as described above will be explained based on FIG. 2.3.

When the target gas enters the sensor while a constant potential VO is applied by the measurement circuit 3, the counter electrode 2 and the working electrode 4
Since an electrolytic current proportional to the gas concentration flows during this period, the resistance value of the sensor 1 changes in proportion to the gas concentration, and the gas concentration is measured. Needless to say, since the reactance coil 5 exhibits an extremely small resistance to direct current, the counter electrode 4 is maintained at approximately ground potential, and the electrode 2
．． Coupled with the fact that the width of the pulse P applied to the sensor is extremely small at 40 μs (Fig. 3), the sensor is unlikely to be affected by the gas measurement operation, even to the point where it exhibits electrochemical behavior. do not have.

On the other hand, the pulse P output from the pulse generator 6 is applied to the working electrode 4 and the reactance coil 5 of the sensor, or the sensor has a counter electrode 2 and a working electrode 4 facing each other with an electrolyte in between. Since this forms a capacitor in terms of alternating current, the pulse P passes through the sensor 1 with a low impedance and flows via the measuring circuit 3 to ground. Therefore, the working electrode 4 is substantially grounded with respect to this pulse P, and no detectable level voltage is generated between the terminals of the reactance coil 5 (11).On the other hand, If the sensor 1 falls off from the measurement circuit 3 for some reason and the lead wire breaks, the pulse generator 6
The pulse from the pulse generator 6 is no longer able to flow to the measurement circuit 3, and instead flows from the reactance coil 5 to the ground. As a result, the pulse P is generated by the reactance coil 5, the resistance,
A transient phenomenon is caused by the capacitance component and an alternating voltage is induced in the reactance coil 5 (■゛).

This alternating voltage is the potential detection transistor T of the measurement circuit.
When the base-emitter voltage V1 of 1 is exceeded, this is made conductive to charge the capacitor C. Since capacitor C constitutes an integrating circuit, it will hold the potential for some time T even after the output of pulse P has stopped, so it should be determined by an alarm circuit etc. within this time T. ,
Alert the operator.

Hereinafter, during the gas concentration measurement period, pulses P are output intermittently, for example, every second, to monitor the connection state of the sensor 1 without impairing its function.

In this embodiment, the induced voltage of the reactance coil 5 is detected by integrating it, but as shown in FIG. By connecting the reactance coil 5 to the set terminal of the mold flip knob and the output terminal of the pulse generator 6 to the clock terminal,
The presence or absence of voltage in the reactance coil is detected in relation to the output timing of the pulse P, or in the case of a microcombuque, it is detected in a certain time relationship T+, T2, T3, etc. with the leading edge or trailing edge of the pulse P.・, T°7, T°2,
It can be detected at T"3... (Fig. 3 II'
).

FIG. 6 shows a second embodiment of the present invention, in which reference numeral 1o denotes a reactance coil formed by transformer-coupling coils 1 and 12, and one coil 12 is connected to the working electrode 4. The electrode 4 is connected to the input terminal of the potential detection circuit 7, and the other coil 1 is connected to the ground.
1 is connected to ground at one end, and to the output terminal of the pulse generator 6 at the other end.

In this embodiment, the DC potential of the measuring circuit 3 is applied from the sensor to ground via the coil 12 to provide an operating voltage to the sensor 1, making it possible to detect the target gas.

On the other hand, the pulses from the pulse generator 6 are input to the coil 11 and then cause the other coil 12 to generate an induced electromotive force. Since this electromotive force flows from the measurement circuit 3 to the ground via the sensor 1, almost no potential is generated in the reactance coil 12.

On the other hand, when the sensor 1 is detached from the measurement circuit 3, the coil 12 is in an open state, so a potential is generated in the coil 12 and the potential detection circuit 7 is activated.

In the above embodiment, the sensor is operated with the working electrode grounded, but as shown in FIG. 7, depending on the type of gas, the opposite electrode 2
If the counter electrode 2 is grounded and used, the counter electrode 2 may be grounded via the reactance coil 5, and the output terminal of the puzzle generator 6 and the input terminal of the potential detection circuit 7 may be connected to the counter electrode 2. It has a similar effect.

In addition, in the above-mentioned embodiments, a two-pole type secessor consisting of a counter electrode and a working electrode was used as an example, but as shown in FIG. The reference potential V between. Even in the constant potential electrolytic gas sensor 21 that applies
In other words, the working electrode or the counter electrode, which is on the ground side, is grounded via the reactance coil 5, and the output terminal of the pulse generator 6 and the potential detection circuit 7 are connected to the grounding side pole.
A similar effect can be achieved by connecting the input terminals of .

Roughly speaking, in the above embodiment, the time width of the monitoring pulse is set to 40 u seconds, but the same effect can be achieved as long as it does not electrochemically affect the sensor, generally 10 milliseconds or less. .

Further, in the above-described embodiments, monitoring is performed at constant intervals of gate opening, but it is clear that detection may be performed at any arbitrary time, such as at the start of measurement, for example.

(Effects) As described above, according to the present invention, one of the working electrode or the counter electrode of a constant potential electrolytic gas sensor is grounded via the inductive reactance coil, and a pulse signal is sent to the grounding side pole. is applied to determine the terminal voltage of the reactance coil, so even if the pulse is as small as possible, it can be reliably detected by the electromotive force of the reactance coil that occurs when the sensor is detached. Moreover, since it does not cause any electrochemical changes to the sensor, it not only eliminates the need for waiting time for the checker, but also makes it possible to monitor sensor fallout even during the measurement period. It is possible to improve reliability by using

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an apparatus showing one embodiment of the present invention, and FIG.
．． Figure 3 is an explanatory diagram and waveform diagram showing the operation of the upper case, and Figure 4 is
．． 5 is a circuit diagram showing one embodiment of the voltage detection circuit shown in the same drawing, FIGS. 6, 7, and 8 are block diagrams showing other embodiments of the present invention, and FIG. 9 is a circuit diagram showing a conventional voltage detection circuit. FIG. 3 is an explanatory diagram showing the operation of the sensor connection determination circuit of FIG. 1... Constant potential electrolytic sensor 2... Counter electrode 3... Sensor output measurement circuit 4... Working electrode 5... Reactance coil 6... Pulse generator 7... ...Potential detection circuit applicant Gustic, Incorporated Riken Keiki Co., Ltd. agent Patent attorney Kei Nishikawa Haruto Kimura Katsuhiko Figure '1 Figure 2 Gas foundation gho Daiiri Safe PPP↓p pop p p 3rd Figure 6 Figure 7-1-Mom T-1 Conflict

Claims (1)

[Claims] One of the working electrode or the counter electrode of the constant potential electrolytic gas sensor is grounded via an inductive reactance element, and
A sensor connection determination circuit in a constant potential electrolytic gas measuring device, comprising means for applying a pulse signal to the ground side pole and means for detecting a terminal voltage of the reactance element.