JP2010266356A - Carbon monoxide gas measuring instrument and alarm - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct the variations in the series internal resistance component of an electrochemical gas sensor. <P>SOLUTION: When the supply of a charge current into the electrochemical gas sensor 1 from a power supply 33 is started, the resistance value of the series internal resistance component Rs in the equivalent circuit of the electrochemical gas sensor 1 is calculated, on the basis of the output voltage outputted from a current/voltage conversion circuit 40 and the resistance value of a resistor by a series internal resistance component calculating means 10a1. Then, the sensitivity data showing the sensitivity of the resistance value of the series internal resistance component Rs in the equivalent circuit with the output of the electrochemical gas sensor 1 is stored in a sensitivity data memory means 10b. Next, the sensitivity of the electrochemical gas sensor 1 is calculated, on the basis of the resistance value calculated by the series internal resistance component calculating means 10a1 and the sensitivity data stored in the sensitivity data memory means 10b by a sensitivity calculating means 10a2, and the concentration of the target gas produced in the electrochemical gas sensor 1 is corrected, on the basis of the sensitivity by a correction means 10a3. <P>COPYRIGHT: (C)2011,JPO&INPIT

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 sectional view in FIG. 11, 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 thus 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

  In the conventional alarm device using the electrochemical gas sensor, the sensitivity of the electrochemical gas sensor is adjusted when the alarm device is built. However, it has been found that the sensitivity of the gas sensor may decrease thereafter. As described above, the gas sensor was considered to be a large capacitor. However, when a misalignment occurs between the conductive hydrophobic film and the electrolyte due to vibration or impact of the alarm, a series resistance is generated by the misalignment. I understood that. And depending on the magnitude | size of DC resistance of a gas sensor, since it will lead to the sensitivity fall of a gas sensor, the quick response was calculated | required. Further, since the conventional sensitivity adjustment is an adjustment including variations in the series resistance of each gas sensor, there is a possibility that the sensitivity of the gas sensor may be lowered depending on the magnitude of the series resistance.

  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 correct variations in the series internal resistance component of an electrochemical gas sensor.

  In order to solve the above problems, the invention according to claim 1 generates a current corresponding to the concentration of the target gas by the reaction between the solid or liquid electrolyte and the target gas, as shown in the basic configuration diagram of FIG. The 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 33 that supplies the charging current to the electrochemical gas sensor 1 to charge the electrochemical gas sensor 1. And a series internal resistance provided in an equivalent circuit at the start of charging of the electrochemical gas sensor 1 provided between the supply path from the power source 33 to the electrochemical gas sensor 1 and the input terminal of the current / voltage conversion circuit 40 A resistor R1 set to a resistance value at which a current flowing from the power source 33 changes in accordance with a change in the resistance value of the component Rs, and the electrochemical gas sensor Serial internal resistance component calculation means 10a1 for calculating the resistance value of the series internal resistance component Rs based on the output voltage from the current / voltage conversion circuit 40 and the resistance value of the resistor R1 at the start of charging. In the carbon oxide gas measuring device, sensitivity information storage means 10b for storing sensitivity information indicating sensitivity between the series internal resistance component Rs and the output of the electrochemical gas sensor 1, and resistance calculated by the series internal resistance component calculation means 10a1 Sensitivity calculation means 10a2 for calculating the sensitivity of the electrochemical gas sensor 1 based on the value and the sensitivity information stored in the sensitivity information storage means 10b, and the electric power based on the sensitivity calculated by the sensitivity calculation means 10a2. And correction means 10a3 for correcting the concentration of the target gas generated by the chemical gas sensor 1.

  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 started, based on the output voltage output from the current / voltage conversion circuit 40 and the resistance value of the resistor, the electrochemical formula The resistance value of the series internal resistance component Rs in the equivalent circuit of the gas sensor 1 is calculated by the series internal resistance component calculation means 10a1. Sensitivity information indicating the sensitivity between the series internal resistance component Rs and the output of the electrochemical gas sensor 1 in the equivalent circuit is stored in the sensitivity information storage unit 10b. Based on the resistance value of the series internal resistance component Rs calculated by the series internal resistance component calculation means 10a1 and the sensitivity information stored in the sensitivity information storage means 10b, the sensitivity of the electrochemical gas sensor 1 is determined by the sensitivity calculation means 10a2. The target gas concentration generated in the electrochemical gas sensor 1 is corrected by the correction means 10a3 based on the sensitivity.

  In order to solve the above-mentioned problem, the invention according to claim 2 is an alarm means 50 for alarming abnormality of the target gas concentration measured by the carbon monoxide gas measuring device, as shown in the basic configuration diagram of FIG. It is characterized by having.

  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 20 is detected, an alarm can be issued by the alarm means.

  As described above, according to the first aspect of the present invention, the electrochemical gas sensor is configured based on the output voltage output from the current / voltage conversion circuit in response to the start of supply of the charging current from the power source to the electrochemical gas sensor. Since the resistance value of the series internal resistance component in the equivalent circuit is calculated, the sensitivity is calculated based on the resistance value and sensitivity information, and the target gas concentration is corrected. Even if an electrochemical gas sensor is misaligned, changed over time, etc., it can be corrected according to its sensitivity, which can contribute to prevention of accuracy degradation. In addition, since the correction can be performed from the output voltage output from the current / voltage conversion circuit according to the start of charging periodically, the maintainability can be improved. Therefore, since the electrochemical gas sensor can accurately measure the target gas concentration, it can 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 in which the carbon monoxide gas measuring device is operating normally by correction 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 graph which shows the measurement result of CO sensitivity. It is a graph which shows the characteristic of sensor sensitivity and additional resistance. It is a graph which shows the relationship between a sensor sensitivity ratio and series resistance Rs. It is a flowchart which shows an example of the self-diagnosis process which CPU of FIG. 2 performs. It is a flowchart which shows an example of the CO detection 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, and in particular, when boiling hot water using a cooking utensil such as a pan or a kettle, until the cold cooking utensil warms 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 (corresponding to a 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. And a capacitor C connected in parallel. 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. Then, at the start of charging ST of the CO sensor 1, the capacitance 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.

  In this way, the series resistance Rs is calculated based on the output voltage of the current / voltage conversion circuit 40. Depending on the magnitude of the series resistance Rs, the ROM 10b or the like has a range, threshold value, etc. that are not problematic in use as a stacking deviation determination condition. By storing in advance, the stacking deviation of the CO sensor 1 can be detected. Therefore, in the present invention, when the CO sensor 1 is charged, it is not regarded as a kind of capacitor, but by focusing on the series resistance Rs of the equivalent circuit, the stacking deviation in the CO sensor 1 can be detected. .

  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, sensitivity correction of the CO sensor 1 will be described below with reference to the drawings of FIGS.

  First, the graph of FIG. 6 shows the result of measuring the sensitivity to CO concentration by sequentially adding any one of 0.2 kΩ, 0.4 kΩ, 0.6 kΩ, and 0.8 kΩ to a certain CO sensor 1. Show. In FIG. 6, the vertical axis represents the output current Iout [μA], and the horizontal axis represents the CO concentration [conc. / Ppm] respectively.

  As shown in FIG. 6, it has been found that the difference in sensitivity does not appear at any low concentration with respect to any of the above four additional resistors, but the gradient of sensitivity falls as the concentration increases. More specifically, the greater the resistance value is such that the additional resistance is 0.8 kΩ, the lower the sensitivity gradient. 7 is a graph showing the relationship between the sensitivity of the CO sensor 1 and the additional resistance. In FIG. 7, the vertical axis represents sensor sensitivity [nA / ppm], and the horizontal axis represents additional resistance [kΩ]. As shown in the graph of FIG. 7, it can be seen that the sensitivity of the CO sensor 1 is lowered.

The graph of FIG. 8 is a graph showing the result of calculating the ratio of sensitivity at each resistance value of the four additional resistors, with the sensitivity when the series resistance Rs is 0Ω being 1 (reference). The linear approximation formula shown in FIG. 8 is y = −0.0974x + 1.0075. Then, when the linear approximation expression is converted into an expression including the series resistance Rs, it is expressed by Expression 1.
y = −0.0974 * (Rs / 1000) +1.0075 Formula 1

  If the series resistance Rs = 500Ω and the detected concentration is 1500 ppm in the above circuit, y = −0.0974 * (500/1000) + 1.0075 = 0.9588. Therefore, (1−0.9588) * 100 = 4.12%, and the sensitivity of 4.12% is reduced.

  Accordingly, since the detected concentration of the CO sensor 1 is actually a concentration increased by 4.12% from 1500 ppm, 1500 ppm * 1.0412 = 1561.8 ppm is an accurate detected concentration. Therefore, in order to correct in such a manner, the above-described linear approximation formula (formula 1) or the like is stored in the ROM 10b, a memory (not shown) or the like as sensitivity information indicating the sensitivity between the series resistance Rs and the output of the CO sensor 1. Thus, the sensitivity can be specified from the resistance value of the series resistor Rs. In addition, as sensitivity information, if sensitivity can be specified from the resistance value of series resistance Rs, it can be set as various different embodiments, such as a conversion table and a conversion program.

  The voice alarm output unit 50 corresponds to a notification unit in the claims, 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.

  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 predetermined diagnosis timing (for example, every 24 hours, every week, etc.). . 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. In step S13, a voltage signal is taken from the operational amplifier 41, and the voltage value is stored in the RAM 10c. In step S14, the CO sensor is based on the voltage value as described above. The resistance value of the first series resistor Rs is calculated and stored in the RAM 10c. In step S15, the first switch SW1 is turned off, and then the process proceeds to step S16.

  In step S16, the sensitivity is calculated based on the resistance value of the RAM 10c and the sensitivity information stored in the ROM 10b (corresponding to sensitivity information storage means) and stored in the RAM 10c, and the resistance value is normal based on the sensitivity. It is determined whether or not. When it is determined that the resistance value is normal (N in S16), the process returns to step S11, and a series of processes is repeated. On the other hand, when it is determined that the resistance value is not normal (Y in S16), the process proceeds to step S17.

  In step S17, sensor failure notification information for notifying the failure of the CO sensor 1 is generated, and the sensor failure notification information is output to the voice alarm output circuit 50, so that the failure of the CO sensor 1 is notified. The process ends.

  As is apparent from the above description, when the CPU 10a executes the self-diagnosis processing program, the CPU 10a functions as the series internal resistance component calculation means 10a1 and the sensitivity calculation means 10a2 in the claims shown in FIG.

  Next, an example of the CO detection 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.

  When the CO detection processing program stored in the ROM 10b is executed by the CPU 10a, it is determined in step S31 whether or not it is a predetermined CO detection timing (for example, a predetermined sampling period). When it is determined that it is not the CO detection timing (N in S31), this determination process is repeated to wait for the CO detection timing. On the other hand, if it is determined that it is the CO detection timing (Y in S31), the process proceeds to step S32.

  In step S32, a voltage signal is taken from the operational amplifier 41, and the voltage value is stored in the RAM 10c. In step S33, the CO operation program is executed, so that the gas concentration is calculated based on the voltage value of the RAM 10c. The gas concentration is corrected based on the correction value corresponding to the sensitivity of the RAM 10c and stored in the RAM 10c, and the process proceeds to step S34.

  In step S34, based on the determination result of the gas concentration in the RAM 10c and the alarm set point, it is determined whether or not it is the CO alarm determination concentration. When it is determined that the concentration is not the CO alarm determination concentration (N in S34), the process returns to step S31, and a series of processes is repeated. On the other hand, when it is determined that the concentration is the CO alarm determination concentration (Y in S34), an alarm is issued from the audio alarm output unit 50 by requesting an alarm from the audio alarm output unit 50, so that the alarm is below the alarm release set point. When this happens, the voice alarm output unit 50 is requested to stop the alarm, and the process is terminated.

  As is clear from the above description, the CPU 10a executes the CO detection processing program, thereby functioning as the correcting means 10a3 in the claims shown in FIG.

  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.

  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. Then, based on the resistance value of the series resistance Rs and the sensitivity information, a correction value for correcting the target gas concentration generated by the electrochemical gas sensor 1 is stored in the RAM 10c or the like.

  When the CPU 10a of the gas alarm device 100 samples the voltage signal output from the current / voltage conversion circuit 40 and measures the gas concentration of the CO sensor 1 at a predetermined sampling period, the gas concentration is determined based on the correction value of the RAM 10c or the like. Correct. The gas alarm device 100 issues an alarm from the audio alarm output unit 50 when the corrected gas concentration becomes equal to or higher than the alarm set point, and stops the alarm when the gas concentration becomes equal to or lower than the alarm release set point.

  According to the gas alarm device 100 described above, the CO based on the output voltage output from the current / voltage conversion circuit 40 in response to the start of supply of the charging current from the power source 33 to the CO sensor (electrochemical gas sensor) 1. Since the resistance value of the series internal resistance component Rs in the equivalent circuit of the sensor 1 is calculated, the sensitivity is calculated based on the resistance value and sensitivity information, and the target gas concentration is corrected. Even if the CO sensor stacking deviation, secular change, or the like occurs due to impact or the like, correction can be made according to the sensitivity, which can contribute to prevention of accuracy degradation. In addition, since the correction can be performed from the output voltage output from the current / voltage conversion circuit 40 in accordance with the start of charging periodically, the maintainability can be improved. Therefore, since the CO sensor 1 can accurately measure the target gas concentration, it can contribute to improving the accuracy of the CO sensor.

  Moreover, according to the gas alarm device 100, the target gas concentration measured in the state of operating normally by the correction described above is determined and the abnormality is alarmed, so that the CO sensor 1 has failed. It 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 concentration of the CO sensor 1 is simply corrected has been described. However, the present invention is not limited to this, and for example, as described above, the slope of the sensitivity of the CO sensor 1 is increased. Various embodiments such as correction in the case of a high concentration of falling asleep can be made.

  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 Series internal resistance component calculation means (CPU)
10a2 Sensitivity calculation means (CPU)
10a3 Correction means (CPU)
10b Sensitivity information storage means (ROM)
31 detection electrode 32 counter electrode 33 power supply (current source)
40 Current / voltage conversion circuit 50 Alarm means (voice alarm output unit)
R1 resistance Rs series resistance (series internal resistance component)
SW1 1st switch

Claims (2)

An electrochemical gas sensor that generates a current corresponding to a target gas concentration by a reaction between a solid or liquid electrolyte and a target gas, a current / voltage conversion circuit that converts the current flowing through the electrochemical gas sensor into a voltage, and the electrochemical formula A power source for supplying a charging current to the gas sensor to charge the electrochemical gas sensor; a supply path from the power source to the electrochemical gas sensor; and an input terminal of the current / voltage conversion circuit; and the electrochemical gas sensor A resistance set to a resistance value at which a current flowing from the power source changes according to a change in a resistance value of a series internal resistance component included in an equivalent circuit at the start of charging, and the current / current at the start of charging of the electrochemical gas sensor The resistance value of the series internal resistance component is calculated based on the output voltage from the voltage conversion circuit and the resistance value of the resistor. And the internal resistance component computing means, the carbon monoxide gas measuring device having,
Sensitivity information storage means for storing sensitivity information indicating sensitivity between the series internal resistance component and the output of the electrochemical gas sensor;
Sensitivity calculation means for calculating the sensitivity of the electrochemical gas sensor based on the resistance value calculated by the series internal resistance component calculation means and the sensitivity information stored in the sensitivity information storage means;
Correction means for correcting the target gas concentration generated in the electrochemical gas sensor based on the sensitivity calculated by the sensitivity calculation 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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