JP5115992B2 - Carbon monoxide gas measuring device and alarm - Google Patents

Description

  The present invention relates to a carbon monoxide gas measuring device and an alarm device for correcting the sensitivity of an electrochemical gas sensor that detects a target gas concentration by an electrochemical reaction of the target gas.

  As a device for measuring the CO concentration in the ambient atmosphere, such as a CO alarm device that detects and alarms CO gas due to incomplete combustion of combustion equipment, etc., a device that has conventionally incorporated an electrochemical CO sensor (= gas sensor) Are known.

  As shown in a cross-sectional view in FIG. 8, this electrochemical CO sensor 1 has a proton conductor film 3 installed in an upper opening 4 of a metal can 2 (= water container) in which water 5 is accommodated. The counter electrode 32 is exposed in the metal can 2, and the metal cap 8 including the gas adsorption filter 8 c is overlapped on the opposite detection electrode 31 and is caulked and fixed to the upper opening 4 of the metal can 2.

In the electrochemical CO sensor 1 having the above-described configuration, CO (= target gas) in the ambient atmosphere is introduced into the inside through the introduction hole 8a of the metal cap 8, and the gas adsorption filter 8c made of activated carbon, silica gel, zeolite, or the like. And through the diffusion control hole 7a of the metal diffusion control plate 7 interposed between the metal cap 8 and the proton conductor film 3, and reaches the detection electrode 31, where the counter electrode Oxidation reaction using the water 5 in the metal can 2 supplied to the proton conductor film 3 from the 32 side is caused to generate protons (2H ⁺ ) and electrons (2e ⁻ ) at the detection electrode 31.

The electrons (2e ⁻ ) generated in the detection electrode 31 cannot pass through the proton conductor film 3 and therefore stay in the detection electrode 31, while the proton (2H ⁺ ) passes through the proton conductor film 3. It moves to the counter electrode 32, where it causes a reduction reaction with oxygen in the metal can 2 to generate water (H ₂ O) at the counter electrode 32.

Accordingly, a metal cap 8 that is electrically connected to the detection electrode 31 via the diffusion control plate 7 and functions as its terminal, and a metal can that is electrically connected to the counter electrode 32 and the washer 9 and functions as its terminal. When a current / voltage conversion circuit (not shown) is connected between the current and voltage, a flow of electrons (2e ⁻ ) staying in the detection electrode 31 toward the counter electrode 32 is generated in the input resistance of the current / voltage conversion circuit. Since a current flows from the counter electrode 32 to the detection electrode 31 through the input resistance, the current / voltage conversion circuit converts this current into current / voltage so that a voltage value corresponding to the CO concentration in the ambient atmosphere can be obtained. A CO concentration signal is obtained (for example, Patent Documents 1 and 2).

  Further, as described above, as a gas sensor that utilizes the reaction between water vapor from a water container and a target gas, an ion conductive solid electrolytic membrane is provided between two electrodes, and a constant relative humidity is maintained in the ion conductive solid electrolytic membrane. There is a gas sensor including a water container filled with water (for example, Patent Document 3).

  The CO sensor 1 itself does not require an external power supply in order to generate a CO concentration signal having a voltage value corresponding to the CO concentration in the ambient atmosphere. Suitable for use with certain CO alarms.

  By the way, the above-mentioned CO alarm device has conventionally performed self-diagnosis for detecting failures such as “no water”, “disconnection”, and “short circuit” in which water in the metal can 2 is reduced (for example, Patent Document 3). . The self-diagnosis of the CO sensor 1 regards this CO sensor 1 as a kind of capacitor, and uses the fact that the current waveform at the time of discharge differs from the normal state due to failures such as “no water”, “disconnection”, and “short circuit”. Is going.

JP 2004-170101 A JP 2004-279293 A JP 2000-146908 A

  However, in the conventional CO alarm device etc., it has been judged until short circuit, disconnection, no water, water depletion, but it has not yet been judged whether the CO sensor 1 is operating normally as a capacitor. It was. In other words, if the CO sensor 1 is not operating normally as a capacitor, the current waveform at the time of discharge may not be accurate. Therefore, if various failures are determined based on the current waveform, the determination accuracy is There was a possibility of decline.

  Therefore, in view of the above-described problems, an object of the present invention is to provide a carbon monoxide gas measuring device and an alarm device that can determine whether an electrochemical gas sensor is normal as a capacitor.

  In order to solve the above-mentioned problem, the invention according to claim 1 generates a current corresponding to the concentration of the target gas by a reaction between the solid or liquid electrolyte and the target gas as shown in the basic configuration diagram of FIG. An electrochemical gas sensor 1, a current / voltage conversion circuit 40 that converts the current flowing through the electrochemical gas sensor 1 into a voltage, and a power source that supplies the charging current to the electrochemical gas sensor 1 to charge the electrochemical gas sensor 1 33, charging control means 10a1 for controlling the supply of charging current from the power source 33 to the electrochemical gas sensor 1 over a predetermined time, and when charging is terminated by the control of the charging control means 10a1, the electrochemical gas sensor 1 A change in the amount of electricity of the capacitor included in the equivalent circuit is detected based on the voltage value of the current / voltage conversion circuit 40. And a self-diagnosis unit 10a3 for diagnosing whether or not the capacitor is normal based on a change in the amount of electricity detected by the amount-of-electricity change detection unit 10a2. To do.

  According to the first aspect of the present invention, when the supply of the charging current from the power source 33 to the electrochemical gas sensor 1 is completed for a predetermined time by the control of the charging control means 10a1, the electric quantity of the capacitor C included in the equivalent circuit of the electrochemical gas sensor 1 Is detected by the electric quantity change detecting means 10a2. Based on the change in the amount of electricity, the self-diagnosis means 10a3 can diagnose whether or not the capacitor C is normal.

  In order to solve the above-mentioned problems, the invention according to claim 2 includes a carbon monoxide gas measuring device 20 according to claim 1 and the carbon monoxide gas measuring device as shown in the basic configuration diagram of FIG. And alarm means 50 for alarming abnormality of the measured target gas concentration.

  According to the second aspect of the present invention, when an abnormality in the target gas concentration measured by the carbon monoxide gas measuring device is detected, an alarm can be issued by the alarm means.

  As described above, according to the first aspect of the present invention, when the supply of the charging current from the power source to the electrochemical gas sensor is completed for a predetermined time, a change in the amount of electricity of the capacitor included in the equivalent circuit of the electrochemical gas sensor is detected. Since it is determined whether or not the capacitor is normal based on the change in the amount of electricity, it can be detected that the electrochemical gas sensor is not operating normally as a capacitor. This can contribute to prevention of accuracy degradation. In addition, since the diagnosis is only based on the output of the current / voltage conversion circuit when the supply of the charging current to the electrochemical gas sensor is completed, it is possible to perform a self-diagnosis periodically and quickly detect an abnormality in the electrochemical gas sensor. Therefore, maintainability can be improved. Therefore, since it can be ensured that the electrochemical gas sensor is operating normally as a capacitor, it is possible to contribute to improving the accuracy of the electrochemical gas sensor.

  As described above, according to the second aspect of the present invention, the target gas concentration measured in a state where the carbon monoxide gas measuring device is operating normally as a capacitor is determined, and the abnormality is alarmed. Therefore, it is possible to prevent the electrochemical gas sensor from being continuously used in a state where a failure has occurred. Accordingly, it is possible to prevent the measurement accuracy of the carbon monoxide gas measuring device from being lowered, thereby contributing to the improvement of safety.

It is a block diagram which shows the basic composition of the carbon monoxide gas measuring device and alarm device of this invention. It is a circuit diagram showing one embodiment of a gas alarm as an alarm according to an embodiment of the present invention. FIG. 3 is an equivalent circuit diagram of an electrochemical gas sensor in the gas alarm device shown in FIG. 2. FIG. 4 is an equivalent circuit diagram at the moment when the electrochemical gas sensor shown in FIG. 3 is charged. It is a graph which shows the relationship between a voltage value and time in an electrochemical gas sensor. It is a figure for demonstrating the calculation example of the capacitor | condenser capacity | capacitance in an electrochemical gas sensor. It is a flowchart which shows an example of the self-diagnosis process which CPU of FIG. 2 performs. It is sectional drawing which shows an example of the electrochemical CO sensor which concerns on this invention.

  Hereinafter, an example of an alarm device having a carbon monoxide gas measuring device according to the present invention will be described with reference to the drawings of FIGS. In addition, the same code | symbol is attached | subjected to the part which is the same as that of what was demonstrated in the prior art, or the detailed description is abbreviate | omitted.

  In FIG. 2, the gas alarm device 100 includes an electrochemical gas sensor (hereinafter referred to as a CO sensor) 1, a microcomputer (hereinafter referred to as a microcomputer) 10, a self-diagnosis circuit 30, a current / voltage conversion circuit 40, and a resistor R1. And a sound alarm output unit 50 and a battery 60 that supplies power to each unit of the gas alarm device.

  The CO sensor 1 is, for example, the electrochemical CO sensor 1 shown in FIG. The CO sensor 1 generates a current I corresponding to the target gas concentration by a reaction between water vapor from a water container containing water or water vapor in the atmosphere and the target gas, and outputs the current I to the current / voltage conversion circuit 40. To do. A resistor R1 is provided between the detection electrode 31 of the CO sensor 1 and the negative input terminal of the operational amplifier 41.

  The current / voltage conversion circuit 40 includes an operational amplifier 41 having a detection electrode 31 and a first switch SW1 of the CO sensor 1 connected to a negative input terminal and a counter electrode 32 and a current source 33 connected to a positive input terminal via a resistor R1. And a feedback resistor R2 provided between the negative input terminal and the output terminal of the operational amplifier 41, and outputs a voltage signal corresponding to the current I to the microcomputer 10.

  The microcomputer 10 includes a CPU 10a that performs various processes according to a processing program, a ROM 10b that stores a program for processing performed by the CPU 10a, a work area that is used in various processes in the CPU 10a, a data storage area that stores various data, and the like. The RAM 10c has a timer 10d for measuring the time set in a predetermined register or the date, time, etc., and these elements are connected by a bus line. The microcomputer 10 samples the voltage signal output from the current / voltage conversion circuit 40 at a predetermined sampling period and measures the CO gas concentration. When the gas concentration reaches or exceeds the alarm set point, a sound alarm is issued. An alarm is issued from the output unit 50, and the alarm is stopped when the alarm is below the alarm release set point.

  Note that CO is known to be generated even when the combustion utensil is used in a normal state. In particular, when boiling hot water using a cooking utensil such as a pan or a kettle, the cold cooking utensil is warmed up. Since CO occurs during this period, even if the CO concentration (gas concentration) exceeds the alarm set point, an alarm is not generated immediately, and the alarm set point is exceeded even after a predetermined delay time has elapsed. If it continues, an alarm may be generated.

  The self-diagnosis circuit 30 is a circuit that executes a self-diagnosis of the CO sensor 1 in accordance with an instruction from the microcomputer 10. The self-diagnosis circuit 30 is provided between the current source 33 and the CO sensor 1 as a power source for charging the CO sensor 1 by supplying a charging current to the CO sensor 1 and the CO sensor 1. 1 and a first switch SW1 for switching between charging and discharging.

  When charged from the current source 33, the CO sensor 1 becomes an equivalent circuit shown in FIG. The equivalent circuit of the CO sensor 1 includes a series resistor (series internal resistance component) Rs electrically connected to the current source 33 and the resistor R1, a resistor Rp connected in series to the series resistor Rs, and a resistor Rp connected in parallel. And a capacitor C. The relationship between the series resistance Rs and the resistance Rp is resistance Rp >> series resistance Rs. The resistance value of the resistor R1 is 1 kΩ, and the resistance value of the feedback resistor R2 is 100 kΩ.

  FIG. 5 shows the relationship between the voltage value of the CO sensor 1 and time corresponding to charging and discharging. In FIG. 5, the vertical axis indicates the voltage value, and the horizontal axis indicates time. In the self-diagnosis operation, the CO sensor 1 is charged to store charges and discharge them. When the battery is charged with a constant current for a certain period of time, the amount of stored charge varies depending on the capacity of the capacitor C. That is, at the end of charging of the CO sensor 1, the voltage value changes depending on the magnitude of the capacitance component. Therefore, the present invention diagnoses the capacitance of the capacitor C by paying attention to the voltage value.

  In the present embodiment, a program for causing the CPU 10a to function as various means such as the charge control means 10a1, the electric quantity change detection means 10a2, and the self-diagnosis means 10a3 in the claim shown in FIG. 1 is stored in the ROM 10b. The electric quantity change detecting means 10a2 calculates the capacitance of the capacitor C.

  First, at the start of charging ST, the capacitive component of the CO sensor 1 can be ignored transiently, and the impedance can be regarded as 0Ω. Then, the CO sensor 1 can be considered as an equivalent circuit shown in FIG.

  The charging current I in FIG. 4 is divided into a current Ia flowing through the series resistor Rs of the CO sensor 1 and a current Ib flowing through the resistor R1. Therefore, the larger the resistance value of the series resistor Rs, the larger the current flowing to the 1 kΩ resistor R1 side. Since the current Ib is converted into a voltage output by the current / voltage conversion circuit 40, the resistance value of the DC resistance Rs of the CO sensor 1 can be calculated based on the voltage value.

  For example, in the configuration described above, the DC resistance Rs is 500Ω and the charging current I is 1 μA. At this time, the ratio of the current flowing through the DC resistor Rs and the resistor R1 is changed from 500Ω: 1 kΩ = 1: 2 to the current on the series resistor Rs side: current on the resistor R1 = 2: 1. When the output voltage is obtained by setting the value of the current flowing through the resistor R1 to X, 1: 2 = X: (1 μA−X), and X = 1/3 μA.

  Therefore, the output voltage of the current / voltage conversion circuit 40 is 1/3 μA * 100 kΩ = 100/3 mV≈33.3 mV. That is, the resistance value of the series resistor Rs can be obtained by performing the reverse calculation described above.

  For example, if the output voltage of the current / voltage conversion circuit 40 is 25 mV, 25 mV / 100 kΩ = 0.25 μA, and 0.25 μA: (1-0.25) μA = 1: 3. Therefore, from 1: 3 = series resistance Rs: 1 kΩ, it can be determined that series resistance Rs = 1000 / 3Ω = 333.3Ω.

  The resistor R1 is an input resistor of the current / voltage conversion circuit 40. The resistor R1 is once electrically connected to the supply path from the current source 33 (power supply) to the CO sensor 1, and the other end is electrically connected to the negative input terminal of the operational amplifier 41 described above. The resistance R1 is set to a resistance value at which the current Ib flowing from the current source 33 increases (changes) in accordance with the increase (change) in the resistance value of the series resistance Rs in the equivalent circuit of the CO sensor 1 described above.

  Next, an example of how to obtain the capacitance component of the capacitor C will be described below with reference to the drawing of FIG. Although the current / voltage conversion circuit 40 in FIG. 6 uses two amplifiers, the basic configuration is the same as that in FIG.

  In the self-diagnosis circuit 30 described above, the determination of the series resistance Rs in the transitional state at the start of charging has been described. When the charging current I is, for example, around 1 μA, the current to the resistor R1 side increases as the voltage across the capacitor C gradually increases at the start of charging. Therefore, the capacity of the CO sensor 1 can be determined by the time constant during charging. However, it is assumed that the resistance Rp in the equivalent circuit is 20 k to 40 kΩ.

  Assuming that the series resistance Rs is 500Ω, the resistance Rp is 40 kΩ, and the voltage of the power supply 33 is 2.4 V, the combined resistance of the series resistance Rs, resistance Rp, and resistance R1 is calculated as (500 + 40k) * 1000 / (500 + 40k) + 1000 = 975.904Ω. When the voltage of the current / voltage conversion circuit 40 is obtained when the capacitor C is fully charged in the equivalent circuit, (2.4V−2.2V) / (975.904 + 200k) * 975.904 = 971. 165 μV.

Assuming that the output voltage is 1.5V, 2.2−1.5 = 0.7V and (0.7 / 16) /68=643.3824 μV. Accordingly, 643.3824 μV = 971.165 μV (1-e ^{(−5 / C * 1000)} ), and C = −0.005 / ln (1−643.3824 μV / 9711.165 μV) = 4.6 mF Can do.

  As described above, since the capacitance of the capacitor C can be obtained, the capacitance component of the CO sensor 1 is almost zero when a short circuit, disconnection, no water, or depletion that may be considered as a sensor failure. It is possible to prevent the CO sensor 1 in a non-existing range from being determined as a failure.

  The audio alarm output unit 50 corresponds to alarm means in the claims shown in FIG. 1 and is electrically connected to the microcomputer 10. The voice alarm output unit 50 is configured to be capable of various outputs such as voice, display, etc. in response to a request from the CPU 10a. In this embodiment, the case where the voice alarm output unit 50 performs voice notification and warning by the voice output circuit will be described. However, the present invention is not limited to this, and various implementations such as notification only by display are provided. It can be in the form.

  Next, an example of the self-diagnosis process according to the present invention executed by the CPU 10a of the gas alarm device 100 will be described below with reference to the flowchart shown in FIG. Note that it is assumed that this process is terminated in response to a termination request from a higher module.

  When the self-diagnosis processing program stored in the ROM 10b is executed by the CPU 10a, it is determined in step S11 whether or not it is a diagnosis timing predetermined by the timer 10d (for example, every 24 hours, every week, etc.). Determined. When it is determined that it is not the diagnosis timing (N in S11), this determination process is repeated to wait for the diagnosis timing. On the other hand, when it is determined that it is the diagnosis timing (Y in S11), the process proceeds to step S12.

  In step S12, the first switch SW1 is turned on. Based on the timer 10d in step S13, a predetermined time (for example, time required for charging the CO sensor 1) has elapsed since the first switch SW1 was turned on. It is determined whether or not. If it is determined that the predetermined time has not elapsed (N in S13), this determination process is repeated to wait for the elapse of the predetermined time. On the other hand, if it is determined that the predetermined time has elapsed (Y in S13), the process proceeds to step S14.

  In step S14, a voltage signal is taken from the operational amplifier 41, and the voltage value is stored in the RAM 10c. In step S15, the resistance value of the series resistance Rs of the CO sensor 1 is calculated based on the voltage value as described above. The data is stored in the RAM 10c, and then the process proceeds to step S16.

  In step S16, based on the voltage value of the voltage signal from the operational amplifier 41, the capacitance of the capacitor C is calculated based on each voltage value as described above, and a change in the amount of electricity in the capacitor C is detected. In step S17, The CO sensor 1 is discharged by turning off the first switch SW1, and then the process proceeds to step S18.

  In step S18, it is determined whether or not the capacitor C is normal based on a comparison result between the detected change in the amount of electricity and a predetermined determination condition. When it is determined that the capacitor C is normal (Y in S18), the process returns to step S11, and a series of processes is repeated.

  On the other hand, when it is determined that the capacitor C is not normal, that is, abnormal (N in S18), in step S19, notification information for notifying the abnormality of the capacitor C is created in the RAM 10c, and the discharge of the capacitor C is performed. After the completion, the notification information is output to the audio alarm output unit 50, whereby the audio alarm output unit 50 notifies the abnormality of the capacitor C by audio, and then returns to step S11 to repeat a series of processes.

  As is clear from the above description, when the CPU 10a executes the self-diagnosis processing program, it functions as the charge control means 10a1, the electric quantity change detection means 10a2, and the self-diagnosis means 10a3 in the claims shown in FIG. In FIG. 7, steps S12 and S17 correspond to the charge control means 10a1, step S16 corresponds to the electric quantity change detection means 10a2, and step S18 corresponds to the self-diagnosis means 10a3.

  Next, an example of the operation (action) of the gas alarm device 100 described above during self-diagnosis according to the present invention will be described below.

  The gas alarm device 100 charges the CO sensor 1 by turning on the first switch SW1 and supplying a charging current from the current source 33 to the CO sensor 1 at the diagnosis timing. The current shunted from the current source 33 is input to the current / voltage conversion circuit 40 via the resistor R1, converted into a voltage by the current / voltage conversion circuit 40, and output. Then, the gas alarm device 100 calculates the resistance value of the series resistance Rs at the moment when charging of the CO sensor 1 is started based on the voltage value from the current / voltage conversion circuit 40 and the resistance R1, and the operational amplifier 41 Based on the voltage value of the voltage signal, the capacitance of the capacitor C is calculated as described above, and the change in the amount of electricity in the capacitor C is detected.

  Thereafter, the gas alarm device 100 turns off the first switch SW1 to discharge the CO sensor 1, and whether the capacitor C is normal based on the comparison result between the change in the amount of electricity of the capacitor C and the determination condition. If it is abnormal, the audio alarm output unit 50 notifies the abnormality of the capacitor C. Accordingly, since the operator can recognize the abnormality of the capacitor C in the CO sensor 1 by the notification, an appropriate response can be performed by sensitivity adjustment or the like.

  According to the gas alarm device 100 described above, when the supply of charging current from the power source 33 to the CO sensor (electrochemical gas sensor) 1 is completed for a predetermined time, the change in the amount of electricity of the capacitor C included in the equivalent circuit of the CO sensor 1 is detected. Since it was detected and it was determined whether or not the capacitor C was normal based on the change in the amount of electricity, it was possible to detect that the CO sensor 1 was not operating normally as the capacitor C, and thus measurement was performed. This can contribute to the prevention of a decrease in accuracy of the target gas concentration. In addition, since the diagnosis is only performed based on the output of the current / voltage conversion circuit 40 when the supply of the charging current to the CO sensor 1 is completed, it is possible to perform a self-diagnosis periodically, and to detect abnormalities in the CO sensor 1. Since the detection can be performed quickly, the maintainability can be improved. Therefore, since it can be ensured that the CO sensor 1 is operating normally as the capacitor C, the accuracy of the CO sensor 1 can be improved.

  Further, according to the gas alarm device 100, since the target gas concentration measured in a state in which the CO sensor 1 is operating normally as the capacitor C is determined and the abnormality is alarmed, the CO sensor 1 is in trouble. Can be prevented from being used continuously. Therefore, since the measurement accuracy of the gas alarm device 100 can be prevented from being lowered, it is possible to contribute to the improvement of safety.

  In the above-described embodiment, the case where the gas alarm 100 calculates the resistance of the series resistance Rs of the CO sensor 1 before calculating the capacity of the capacitor C has been described. However, the present invention is not limited to this. For example, the resistance of the series resistor Rs can be stored in advance in the ROM 10b, a memory (not shown) or the like, and the calculation of the resistance value can be omitted by using this.

  In the above-described embodiment, the case where the gas alarm device 100 notifies when the abnormality of the capacitor C is detected has been described. However, the present invention is not limited to this, and the sensitivity of the CO sensor 1 is corrected. It can be set as various different embodiments.

  In the above-described embodiment, the case where the carbon monoxide gas measuring device of the present invention is applied to the alarm device 100 has been described. However, the present invention is not limited to this, and for example, the carbon monoxide gas measuring device is Various embodiments can be made such as incorporating a carbon monoxide gas measuring apparatus as a single measuring instrument incorporated in various devices such as a combustion instrument and a fire alarm.

  Further, in the self-diagnosis method described above, water vapor from a water container containing water or water vapor in the atmosphere is used as an electrolyte, and the CO sensor 1 generates a current corresponding to the target gas concentration by the reaction between the water vapor and the target gas. The case where it occurs is explained. Instead, it can be applied to an electrochemical sensor composed of two or three electrodes using sulfuric acid as an electrolyte. For example, the detection target gas includes a pair of electrodes in contact with a solid or liquid electrolyte, and the detection target gas based on a current flowing between the detection electrode to which the detection target gas reacts and the other electrode or a voltage corresponding to the current. The present invention can also be applied to an electrochemical gas sensor that detects the concentration of the gas.

  As described above, the above-described embodiments are merely representative forms of the present invention, and the present invention is not limited to the embodiments. That is, various modifications can be made without departing from the scope of the present invention.

1 Electrochemical gas sensor (CO sensor)
2 Metal can (water container)
10a1 Charge control means (CPU)
10a2 Electric quantity change detecting means (CPU)
10a3 Self-diagnosis means (CPU)
31 detection electrode 32 counter electrode 33 power supply (current source)
40 Current / voltage conversion circuit 50 Alarm means (voice alarm output unit)
C Capacitor R1 Resistance Rs Series resistance (series internal resistance component)
SW1 1st switch

Claims (2)

An electrochemical gas sensor that generates a current corresponding to the concentration of the target gas by a reaction between the solid or liquid electrolyte and the target gas;
A current / voltage conversion circuit for converting the current flowing through the electrochemical gas sensor into a voltage;
A power source for charging the electrochemical gas sensor by supplying a charging current to the electrochemical gas sensor;
Charging control means for controlling the supply of charging current from the power source to the electrochemical gas sensor over a predetermined time;
An electric quantity change detecting means for detecting a change in the electric quantity of a capacitor included in an equivalent circuit of the electrochemical gas sensor based on a voltage value of the current / voltage conversion circuit when charging is terminated by the control of the charging control means. When,
Self-diagnosis means for diagnosing whether or not the capacitor is normal based on a change in the amount of electricity detected by the electricity amount change detection means;
A carbon monoxide gas measuring device comprising: A carbon monoxide gas measuring device according to claim 1;
Alarm means for alarming abnormality of the target gas concentration measured by the carbon monoxide gas measuring device;
An alarm device comprising:

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