JP5822566B2 - Method of using electrochemical sensor and alarm device using electrochemical sensor - Google Patents

Description

  The present invention is such that the detection electrode to which the detection target gas reacts and the counter electrode to which oxygen reacts are connected to both sides of the electrolyte layer, and the detection target gas contained in the outside air contacts the detection electrode at a diffusion-controlled rate. Using an electrochemical sensor provided with a diffusion control means having a diffusion control hole for controlling the inflow amount of the outside air, a current flowing from the counter electrode to the detection electrode via an external short circuit flows in a reverse direction. The present invention relates to a method for using an electrochemical sensor in an alarm device provided with a determination unit that determines that the sensor is abnormal when the current flows as a negative current. Moreover, it is related with the alarm apparatus using the electrochemical sensor which enforces such a usage method.

As one of sensors mounted on an alarm device or the like, for example, there is a CO sensor that detects carbon monoxide gas. As a detection method of the CO sensor, an electrochemical method as shown in Patent Document 1 is known. The electrochemical sensor is generally configured by sandwiching an electrolyte solution or a solid electrolyte between a detection electrode and a counter electrode.
Note that the electrochemical sensor described in this specification particularly includes an electrolyte solution, an electrode, and a gas permeable membrane. The detection principle of this electrochemical sensor will be described using a CO sensor that detects carbon monoxide gas as an example.

When carbon monoxide, which is a gas to be detected, comes into contact with the detection electrode of the CO sensor, as shown in the following (1), carbon monoxide and water react with each other to generate carbon dioxide and proton (H ⁺ ) And electrons (e ⁻ ) are generated.
CO + H ₂ O → CO ₂ + 2H ⁺ + 2e ⁻ (1)
The reaction (1) is a diffusion-controlled reaction that depends on the rate at which carbon monoxide diffuses in the measurement atmosphere under conditions where there are diffusion control holes and the like as in this case (oxygen and carbon monoxide coexist). In the vicinity of the mixed potential of the sensing electrode, the oxidation reaction of carbon monoxide is diffusion-limited.)

Protons (H ⁺ ) generated at the detection electrode pass through the electrolyte and move to the counter electrode side. Furthermore, the electrons (e ⁻ ) generated at the detection electrode pass through the external circuit and move to the counter electrode, and react with oxygen introduced into the counter electrode and water in the electrolyte as shown in (2) below. (OH ⁻ ) is generated. Since oxygen is also present at the detection electrode, generally about half of the carbon monoxide is oxidized with oxygen at the detection electrode, and the other half is oxidized with oxygen at the counter electrode.
1 / 2.O ₂ + H ₂ O + 2e ⁻ → 2OH ⁻ (2)

  In this way, the electrical characteristics of electrons (corresponding to the above-described positive current flow state) flowing through the external circuit from the detection electrode side to the counter electrode side in accordance with the above reaction are detected as, for example, a short-circuit current value. The concentration of carbon monoxide in the atmosphere can be measured, or the concentration of carbon monoxide in the measurement atmosphere can be measured by detecting the open circuit voltage with the detection electrode and the counter electrode being in an open circuit state.

  By the way, since the alarm device is a safety device, it is necessary to avoid as much as possible that the alarm cannot be normally performed due to problems such as failure to turn on the power, deterioration of gas sensor sensitivity, and circuit failure. is there. For this reason, in recent years, a self-diagnosis function has been installed in an alarm device that detects a sign of a failure of a sensor or a circuit when the alarm device itself is energized and notifies that there is a risk of failure.

  In the case of the above-described electrochemical sensor, due to the characteristics of the sensor and the configuration of the detection circuit, when the gas is detected normally, a signal is output only in either positive or negative direction (hereinafter, the normal signal is assumed to be positive). To do). For this reason, in an alarm device using an electrochemical sensor, the sensor may fail if the sensor self-diagnosis function has an output in which positive and negative are reversed (negative) compared to a normal function. It is common to be configured to notify that there is.

JP 2004-279293 A

  By the way, an alarm device using an electrochemical sensor may be sprayed with a different type of inspection gas from the gas to be detected by the sensor when the alarm device is inspected, for example. At this time, the inventors experimentally found that, depending on the electrochemical sensor, a positive output is temporarily output after a positive output. Here, in the case of an electrochemical CO sensor, the inspection gas is hydrogen gas, and its concentration is usually high.

  In such a case, although the sensor itself has not failed, the alarm device determines that there is a possibility of failure of the sensor by the above self-diagnosis function, so the user needs to replace the alarm device. There is a risk of misunderstanding.

  The present invention has been made in view of the above problems, and its purpose is not to make an erroneous determination even when an inspection gas is blown in an alarm device using an electrochemical sensor, and is normally used. It is an object of the present invention to establish a method for using an electrochemical sensor that can normally determine that there is a possibility of failure.

The characteristic configuration of the method of using the electrochemical sensor according to the present invention is that the detection electrode to which the detection target gas reacts and the counter electrode to which oxygen reacts are connected to both sides of the electrolyte layer, and the detection target gas contained in the outside air includes Using an electrochemical sensor comprising a diffusion control means formed with a diffusion control hole for controlling the inflow amount of the outside air so as to come into contact with the detection electrode at a diffusion rate, the counter electrode to the detection electrode via an external short circuit A current flowing in the positive direction, a current flowing in the opposite direction as a negative current, and a method of using an electrochemical sensor in an alarm device provided with a determination means for determining that the sensor is abnormal when the negative current flows , after pre-Symbol plus current is detected, without determines that the negative current is abnormal when it is detected, determine the constant stopped for a predetermined time period, the determination by the determining means It is to stop.

  As a result of the intensive studies by the inventors, the following has been found regarding the relationship between the electrochemical sensor and the inspection gas. In an alarm device using an electrochemical sensor equipped with a diffusion control means, even when the inflow amount of gas entering the sensor means is controlled by the diffusion control means, an inspection gas having a faster diffusion speed than the detection target gas has entered. In such a case, the inspection gas circulates to the counter electrode side in addition to the detection electrode side. As a result, an oxidation reaction occurs at both the detection electrode and the counter electrode, thereby extremely reducing the sensitivity of the sensor means to the gas. In particular, since the inspection gas generally has a high concentration, this phenomenon is likely to occur. Therefore, when the sensor means is exposed to the inspection gas, the gas stays on the counter electrode side immediately after the start of exhaust. Also, during exhaust, the gas escapes from the detection electrode side. For this reason, it has been found that for a while, the counter electrode side reacts more with the gas than the detection electrode side, and a current flows from the counter electrode side to the detection electrode side (a negative current flows).

  In this regard, in the feature configuration of the present application, when a negative current is detected after a positive current is detected, the determination by the determination unit is stopped for a predetermined period of time after the detection of the negative current. For this reason, even when the inspection gas is sprayed, there is no false detection that the sensor may be damaged by a negative current temporarily generated after the positive current. Further, with such a configuration, when a failure occurs in the sensor during normal use, a negative current flows from a state where there is no output, so that it is possible to normally detect the possibility of failure.

  In the method for using the electrochemical sensor according to the present invention, it is preferable that when the electrochemical sensor is turned on, the determination by the determination unit is stopped for a predetermined period after the power is turned on.

According to the method of using the electrochemical sensor of this configuration, when the power is turned on, the determination by the determining means is stopped for a predetermined period after the power is turned on, regardless of the output of the electrochemical sensor.
Therefore, in this configuration, for example, even if a negative current flows due to external factors such as electromagnetic waves within a predetermined period after turning on the power when installing an alarm device in a house, it is erroneously assumed that the sensor may be damaged. There is no detection. Also, in such a configuration, if a predetermined period has passed since the power was turned on, the determination means determines that the sensor is abnormal when a negative current flows. It is possible to determine.

  In the method of using the electrochemical sensor according to the present invention, it is preferable that the determination unit determines that the electrochemical sensor is abnormal when the negative current continues to flow for a predetermined determination period.

According to the method of using the electrochemical sensor of this configuration, when a negative current flows, it is not immediately determined that the alarm device has failed, and after confirming that the negative current continues to flow for a predetermined determination period, It is determined that there is an abnormality.
Therefore, in this configuration, it is determined that there is an abnormality in the sensor only when a negative current continues to flow due to a failure, and it is not determined that there is an abnormality if the negative current only flows for a shorter period than the predetermined determination period. For example, it is possible to reduce the possibility of erroneous determination when a negative current temporarily flows due to noise from the outside of the alarm device, and to determine that there is an abnormality in the sensor with higher accuracy.

The characteristic configuration of the alarm device according to the present invention is that sensor means in which a detection electrode to which a detection target gas reacts and a counter electrode to which oxygen reacts are connected to both sides of the electrolyte layer, and the detection target gas contained in the outside air is in the detection pole. And an electrochemical sensor having a diffusion control means formed with a diffusion control hole for controlling the inflow amount of the outside air so as to come into contact at a diffusion-controlled rate, from the counter electrode to the detection electrode via an external short circuit the current through the current through positive current, in the opposite direction as the negative current, a warning device which includes a determination means and sensor is abnormal when the negative current flows, before Symbol plus current is detected after without determines that the negative current is abnormal when it is detected, determine the constant stopped for a predetermined period of time it is to a judging stopping means for stopping the determination by the determination means.

  In the above characteristic configuration, when a negative current is detected after the positive current is detected by the stop means, the determination by the determination means can be stopped for a predetermined period of stoppage after detection of the negative current. For this reason, even when the inspection gas is sprayed, there is no false detection that the sensor may be damaged by a negative current temporarily generated after the positive current. Further, with such a configuration, when a failure occurs in the sensor during normal use, a negative current flows from a state where there is no output, so that it is possible to normally detect the possibility of failure.

  The alarm device according to the present invention preferably includes a power-on stop unit that stops the determination by the determination unit for a predetermined period after the power is turned on when the electrochemical sensor is turned on.

According to the alarm device of this configuration, when the power is turned on, the power-on stop means stops the determination by the determination means for a predetermined period after the power is turned on regardless of the output of the electrochemical sensor.
Therefore, in this configuration, for example, when a warning device is installed in a house, even if a negative current flows due to external factors such as electromagnetic waves within a predetermined period after the power is turned on, it is erroneously detected that the sensor may be broken. There is nothing to do. Also, in such a configuration, if a predetermined period has passed since the power was turned on, the determination means determines that the sensor is abnormal when a negative current flows. It is possible to determine.

  Further, it is preferable that the determination unit determines that the electrochemical sensor is abnormal when the negative current continues to flow for a predetermined determination period.

According to the alarm device of this configuration, the determination unit does not immediately determine that the electrochemical sensor has failed when a negative current flows, and after confirming that the negative current continues to flow for a predetermined period of time, It is determined that the chemical sensor is abnormal, that is, it has failed.
Therefore, in this configuration, it is determined that there is an abnormality in the sensor only when a negative current continues to flow due to a failure, and it is not determined that there is an abnormality if the negative current only flows for a shorter period than the predetermined determination period. For example, it is possible to reduce the possibility of erroneous determination when a negative current temporarily flows due to noise from the outside of the alarm device, and to determine that there is an abnormality in the sensor with higher accuracy.

Schematic showing the appearance of the alarm device in the present embodiment A longitudinal sectional view showing the overall configuration of the electrochemical sensor in the present embodiment Longitudinal sectional view of the sensor body, which is the main part of the electrochemical sensor Basic measurement circuit diagram using a bipolar electrochemical sensor Graph showing the results of preliminary tests Diagram showing the difference in potential between the anode (detection) and cathode (counter) in an electrochemical sensor Graph showing characteristics of electrochemical sensor

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the configurations described in the embodiments and drawings described below, and various modifications are possible.

1. Mechanical structure of the device (appearance structure of alarm device)
An appearance of the alarm device 60 in the present embodiment is shown in FIG. The alarm device 60 includes a substantially rectangular parallelepiped casing 61. In the casing 61, various sensors such as the electrochemical sensor 100 and the methane sensor 101 and various processes to be described later are performed based on output signals from the sensors. The microcomputer 205 is included. On one surface of the housing 61, an inspection port 62 for blowing inspection gas to various sensors is provided.

  The internal configuration of the alarm device 60 is shown in FIG. The electrochemical sensor 100 and the methane sensor 101 are disposed at a position adjacent to the inspection port 62 as viewed in the axial direction of the inspection port 62 (as viewed from the front and back direction in FIG. 1). For this reason, the inspection gas that has entered from the inspection port 62 is sprayed onto both the electrochemical sensor 100 and the methane sensor 101. More specifically, regarding the positional relationship of the sensors, the methane sensor 101 is disposed at a position overlapping the inspection port 62 when viewed in the axial direction of the inspection port 62. An electrochemical sensor 100 is disposed adjacent to the methane sensor 101.

[Basic structure of electrochemical sensor]
FIG. 2 is a longitudinal sectional view showing the entire configuration of the electrochemical sensor 100 used in the method of using the electrochemical sensor of the present invention. FIG. 3 is a longitudinal sectional view of the sensor main body 10 which is a main part of the electrochemical sensor 100.

  Specifically, the electrochemical sensor 100 of the present embodiment is a CO sensor using carbon monoxide as a detection target gas, and includes a sensor body 10, a water tank 20, a filter unit 30, a washer 40, and a basic structure thereof. A gasket 50 and the like are provided.

なお、電解質層１には、図示しない参照電極を介在させても構わない。この場合、電解質層１を上下二層に分割し、両層の間に参照電極を挟み込む。 As shown in FIG. 3, the sensor body 10 includes sensor means 11 having a laminated structure in which an anode electrode 2 as a detection electrode and a cathode electrode 3 as a counter electrode are connected to both sides (upper and lower surfaces) of the electrolyte layer 1, respectively. Conductive hydrophobic films 4 and 5 described later and a diffusion control plate 6 are provided.
In the electrolyte layer 1, as will be described later, cations such as protons (H ⁺ ) generated by the oxidation reaction of carbon monoxide at the anode electrode 2 move to the cathode electrode 3 (or from the cathode electrode 3 to OH ⁻ or the like). For example, a base such as a filter paper is impregnated with an electrolyte containing an aromatic sulfonate (polymer) represented by the following chemical formula. Can do.

Note that a reference electrode (not shown) may be interposed in the electrolyte layer 1. In this case, the electrolyte layer 1 is divided into two upper and lower layers, and a reference electrode is sandwiched between both layers.

  The anode 2 is an electrode catalyst that oxidizes carbon monoxide to carbon dioxide, and a platinum catalyst or the like is generally used. The cathode electrode 3 has substantially the same configuration as the anode electrode 2. In the present embodiment, the film thicknesses of the anode electrode 2 and the cathode electrode 3 are set to about 0.05 to 0.2 mm, respectively.

  Conductive hydrophobic films 4 and 5 are provided above the anode 2 and below the cathode 3, respectively. The conductive hydrophobic films 4 and 5 are configured as gas permeable films capable of transmitting gases (carbon monoxide, carbon dioxide, water vapor, and oxygen) involved in the reaction at the anode 2 or the cathode 3.

A diffusion control plate 6 is provided above the conductive hydrophobic film 4 above the anode electrode 2. The diffusion control plate 6 controls the inflow amount of the outside air so that the carbon monoxide gas contained in the outside air contacts the anode electrode 2 at the diffusion rate. Specifically, a diffusion control hole 6a is formed in the diffusion control plate 6, and the supply amount of outside air and carbon monoxide molecules supplied to the anode electrode 2 through the diffusion control hole 6a is controlled. Therefore, if the concentration of carbon monoxide contained in the outside air is high and carbon monoxide is introduced into the anode electrode 2 as it is, the oxidation reaction at the anode electrode 2 cannot catch up due to excess carbon monoxide. Even in this case, the oxidation reaction of all the carbon monoxide can be completed at the anode 2 by the action of the diffusion control hole 6 a provided in the diffusion control plate 6.
In this embodiment, the diffusion control plate 6 is formed of a thin plate made of a metal such as stainless steel, and the diffusion control hole 6a is formed by an arbitrary method such as punching.

  A water tank 20 is connected below the sensor body 10 on the cathode electrode 3 side. The water tank 20 has a constricted portion 22 formed in a part of the outer wall 21, and a washer 40 having a hole portion 41 formed in the central portion is moored at the constricted portion 22. In the space X surrounded by the outer wall 21 and the washer 40, water or a water absorbent resin 23 that has absorbed water is accommodated. Water existing in the space X passes through the hole 41 of the washer 40 in the state of water vapor, and is supplied to the electrolyte layer 1 through the cathode electrode 3 of the sensor body 10.

  On the other hand, a filter unit 30 is provided above the sensor body 10 on the anode electrode 2 side. The filter unit 30 forms a hollow portion Y by caulking the lower half portion 32 formed with the second vent holes 32a to the upper half portion 31 formed with the first vent holes 31a, and the activated carbon filter 33 is formed in the hollow portion Y. It has a configuration filled with. In this configuration, carbon monoxide contained in the outside air enters from the first ventilation hole 31a, and after impurities and the like are removed by the activated carbon filter 33, the carbon monoxide is supplied from the second ventilation hole 32a to the anode 2 of the sensor body 10. The

  A gasket 50 is provided between the filter unit 30 and the outer wall 21 of the water tank 20 so that water vapor evaporated from the water tank 20 does not leak outside.

  In the electrochemical sensor 100 of the present invention, the bottom surface 24 of the water tank 20 and the top surface 31b of the upper half 31 function as electrode terminals. Accordingly, the upper half 31 and the lower half 32 of the filter unit 30, the diffusion control plate 6 of the sensor body 10, the washer 40, and the outer wall 21 of the water tank 20 are made of a conductive material such as metal. On the other hand, the gasket 50 is made of an insulating material.

[Measurement circuit]
The electrochemical sensor 100 configured in this manner is incorporated into a basic measurement circuit 200 as shown in FIG. 4, for example. The basic measurement circuit 200 is used in a measurement method when the electrochemical sensor 100 is a bipolar type.

  A minute current (short-circuit current) generated from the sensor body 10 of the electrochemical sensor 100 is amplified and converted by the operational amplifier 201, the resistor 202, and the capacitor 203, and the voltage Vout (output of the electrochemical sensor) is output from the output terminal 204. ) Is output. From the output result, the electrochemical sensor 100 detects the concentration of carbon monoxide contained in the outside air. The short-circuit current flows from the anode 2 to the cathode 3 in the electrolyte, and from the cathode 3 to the anode 2 in the external circuit. Normally, the voltage Vout increases as the carbon monoxide concentration increases. In the normal state referred to in the present application in which the diffusion control hole 6a is opened, a slight positive current (in the same direction as when carbon monoxide is detected) due to the influence of a reducing gas such as carbon monoxide existing in the atmosphere. Becomes a plus).

2. Abnormal state of the electrochemical sensor In the electrochemical sensor 100 including the diffusion control plate 6, it is important to maintain the diffusion control hole 6a in a healthy state in order to accurately detect the concentration of the detection target gas. It is. However, for example, in an environment where the temperature change is large, there is a possibility that the diffusion control hole 6a is blocked by the dew condensation water and the diffusion control hole 6a is partially or completely blocked, thereby reducing the diffusibility.

  First, with respect to the diffusion control plate 6 of the electrochemical sensor 100, a preliminary test was performed to confirm what kind of difference occurs in the output voltage depending on the presence or absence of the diffusion control hole 6a. The test results are shown in FIG. In FIG. 5, (a) shows a case where the diffusion control hole 6a is provided in the diffusion control plate 6 and corresponds to a normal state (completely open state) in which the diffusion control hole 6a is not partially or completely closed. Further, (b) is a case where the diffusion control hole 6a is not provided in the diffusion control plate 6, and an abnormal state (incomplete opening state) in which the diffusion control hole 6a is partially or completely closed and the diffusibility is lowered. , Fully closed state).

  Here, in the preliminary test, the electrochemical sensor in which the diffusion control hole 6a is provided in the diffusion control plate 6 is performed using 20 electrochemical sensors. In FIG. 5A, among the 20 electrochemical sensors, the output voltage indicates the maximum voltage value, the output voltage indicates the minimum voltage value, and the output voltage is the maximum and minimum. A part of the voltage values are shown, and the rest are omitted. Further, in the preliminary test, 20 electrochemical sensors are also used for the electrochemical sensor in which the diffusion control plate 6 is not provided with the diffusion control hole 6a. In FIG. 5B, among the 20 electrochemical sensors, the output voltage indicates the maximum voltage value, the output voltage indicates the minimum voltage value, and the output voltage is the maximum and minimum. A part of the voltage values are shown, and the rest are omitted.

In FIG. 5A corresponding to the normal state, all the output voltages of the 20 electrochemical sensors were always higher than the baseline of 1 V (that is, a positive short-circuit current was generated). On the other hand, in FIG. 5B corresponding to the state in which the diffusivity is lowered, all the output voltages of the 20 electrochemical sensors were always lower than the baseline of 1 V (that is, a negative short-circuit current). Occurs). From these results, it is considered that it is possible to determine whether or not the diffusibility is lowered by monitoring the output current of the electrochemical sensor 100.
In this preliminary test, the output voltage is monitored as an electrical characteristic between the electrodes of the electrochemical sensor 100, but the same result can be obtained even with the output current.

In the electrochemical sensor 100, when a potential difference is generated between the anode electrode 2 and the cathode electrode 3, a current (short circuit current) flows between both electrodes. Here, the reaction occurring at the anode electrode 2 and the cathode electrode 3 in a general air atmosphere is an equilibrium reaction represented by the following (3).
O ₂ + 2H ₂ O + 4e ⁻ ← → 4OH ⁻ (3)
Incidentally, this reaction corresponds to the equation (2) described in the section of the prior art. Here, FIG. 6A shows the level of the equilibrium potential of the anode electrode 2 and the equilibrium potential of the cathode electrode 3 in a normal state where the diffusibility is not lowered, and FIG. In the state where the property is lowered, the level of the equilibrium potential of the anode electrode 2 and the equilibrium potential of the cathode electrode 3 is shown. Incidentally, the equilibrium potential E _eq due to the reaction of (3) above is assumed that the partial pressure of oxygen is P _O2 , the activity of OH ⁻ is a _OH− , a _OH = 1 and P _O2 = 1 and the potential is E _0. From the Nernst equation, it is expressed as (4) below (at a temperature of 25 ° C.).

As shown in FIG. 6A, in a normal state where the diffusibility is not lowered, the equilibrium potential of the anode electrode 2 is lower than the equilibrium potential of the cathode electrode 3. This is due to the influence of the oxidation reaction of a reducing gas such as a small amount of carbon monoxide in the atmosphere. However, in the above (4), when the oxygen partial pressure P _O2 decreases (that is, when the reacting oxygen is deficient), the equilibrium potential decreases, but the influence on the cathode electrode 3 is greater than that on the anode electrode 2. This is because the humidity in the sensor body increases due to a decrease in diffusibility, and the cathode electrode 3 (lower side) is closer to the water tank 20 than the anode electrode 2 (upper side). This is presumably because dew condensation preferentially occurs in the hydrophobic membrane and the oxygen partial pressure (P _O2 ) becomes lower. As a result, the decrease in the equilibrium potential at the cathode electrode 3 is large, and the equilibrium potential at the anode electrode 2 is higher than the equilibrium potential at the cathode electrode 3 as shown in FIG. Therefore, in the normal state shown in FIG. 6A and the diffusibility state shown in FIG. 6B, the equilibrium potential of the anode electrode 2 and the equilibrium potential of the cathode electrode 3 are used. The short-circuit current flowing between the anode 2 and the cathode 3 becomes a positive current when it is normal, but becomes a negative current after the diffusibility is reduced (electrolyte). The direction in which the inside flows from the anode 2 to the cathode 3 is positive).

  Therefore, during normal use, it is possible to detect a short-circuit current flowing between the anode 2 and the cathode 3 and determine that the sensor is abnormal when a negative current flows.

The alarm device according to the present invention has a gas detection measurement function for detecting a detection target gas and measuring the concentration thereof, and an abnormality detection function for detecting an abnormality of the electrochemical sensor 100 when the above-described negative current flows. I have. In principle, these gas detection function and abnormality detection function are configured to work as long as the power is turned on in the operation of the alarm device.
It is an object of the present invention to prevent the abnormality detection function from functioning during the inspection work or for a certain period immediately after the power is turned on.

  Hereinafter, the cause of the necessity of stopping the abnormality detection function and the phenomenon occurring in the situation will be described together with the structure of the alarm device.

  As shown in FIG. 4, the electrochemical sensor 100 is incorporated in the basic measurement circuit 200, and a microcomputer 205 is connected between the output terminals 204 and provided in the alarm device 60. In FIG. 4, a microcomputer is drawn separately for easy understanding. The microcomputer 205 performs measurement on the software to perform measurement steps for measuring plus and minus of the short-circuit current and the magnitude thereof (which performs the detection and measurement function) 211a. Determination means (executing the abnormality detection function) 211b for executing a step, determination stop means 212 for executing a determination stop step, and power-on stop means 213 for executing a power-on stop step are configured. . (Each step will be described later).

3. Characteristics of Electrochemical Sensor FIG. 7A shows the output when carbon monoxide gas is blown onto the CO sensor as the electrochemical sensor 100 according to the present embodiment (applied between the anode electrode 2 and the cathode electrode 3). Voltage value). In taking the data of FIG. 7A, carbon monoxide gas having a concentration of 30, 100, 300, 650, and 3000 ppm was blown stepwise using 119 electrochemical sensors. In FIG. 7A, among 119 electrochemical sensors, the output voltage indicates the maximum voltage value, the output voltage indicates the minimum voltage value, and the output voltage is between the maximum and minimum values. A part of the voltage values is shown, and the rest are omitted.

As can be seen from FIG. 7A, when carbon monoxide gas is sprayed on the electrochemical sensor according to the present embodiment, a stable positive output above 1 V (reference potential) is obtained regardless of the concentration. .
The measuring means 211a executes CO detection and concentration specification from this output.

FIG. 7B shows an output when H ₂ gas, which is generally used as an inspection gas, is sprayed on the CO sensor as the electrochemical sensor according to the present embodiment. In obtaining the data of FIG. 7B, 119 electrochemical sensors were used, and H ₂ gas having a concentration of 30, 100, 300, 650, and 3000 ppm was blown stepwise. In FIG. 7B, among 119 electrochemical sensors, the output voltage indicates the maximum voltage value, the output voltage indicates the minimum voltage value, and the output voltage is between the maximum and minimum values. A part of the voltage values is shown, and the rest are omitted.

As can be seen from FIG. 7B, when H ₂ gas is sprayed on the electrochemical sensor according to the present embodiment, an electrochemical sensor showing an output of 1 V or less immediately after spraying a high concentration of H ₂ gas of 3000 ppm. Existed. In addition, although not shown in figure, the output below 1V was confirmed by the majority of 119 electrochemical sensors. In this experiment, a negative output of 1 V or less was applied for about 1500 s from immediately after 3000 ppm of H ₂ gas was sprayed (1680 s on the horizontal axis in FIG. 7B) to 3120 s on the horizontal axis in FIG. 7B. confirmed.

That is, as described in the item of the problem to be solved by the invention and the item of means for solving the problem, when the inspection gas is blown, the sensor is temporarily out of order. It turned out that a negative current may flow.
Therefore, a determination stop unit 212 that temporarily stops the determination of the determination unit 211b is provided.

4). Stopping the abnormality detection function In the alarm device according to the present application, the following steps <1> to <3> are repeatedly executed at predetermined intervals in association with the abnormality detection function.
<1> A measurement step in which the measuring unit 211a measures the state of a short current flowing between the anode 2 and the cathode 3.
<2> When the current state measured by the previous measurement step is a positive current, even if the current state measured by the measurement step is a negative current, A determination stop step for stopping the determination in the determination step <3> described below after a detection for a predetermined period of determination stop. In other words, this step skips the following determination step for a predetermined period of time when the negative current is detected immediately after the positive current is detected. Then, after the determination stop predetermined period has elapsed, the following determination step is executed.
<3> The determination unit 211b executes a determination step of determining that an abnormality has occurred in the electrochemical sensor 100 when a negative current continuously flows for a predetermined period of time.

  The determination stop predetermined period in the determination stop step <2> is preferably set based on the time during which a negative current is generated when the electrochemical sensor 100 detects the inspection gas. Here, as the determination stop predetermined period, for example, 60 minutes can be adopted.

  In this embodiment, in the determination step <3>, it is determined that the electrochemical sensor 100 is abnormal only when a negative current continues to flow for a predetermined determination period. That is, when a positive current is detected within a predetermined period after the negative current starts to flow, it is determined that there is no abnormality. Here, for example, 120 minutes can be adopted as the predetermined determination period.

In the above <1>, the “short current” corresponds to one of the electrical characteristics. This “short current” is a current when the anode 2 and the cathode 3 are short-circuited.
In the above <2>, the “state of current measured in the previous measurement step” can be stored in, for example, a memory (not shown).

  In this embodiment, the <4> power-on stop means 213 unconditionally makes a determination in the determination step for a predetermined period after the power is turned on when the electrochemical sensor 100 is turned on. Execute the power-on stop step to stop In other words, immediately after the power is turned on, the determination step <3> is forcibly skipped when executing the above steps <1>, <2>, and <3> for a predetermined period after the power is turned on.

  As the predetermined period after power-on in the power-on stop step, for example, it is preferable to set a time longer than that required for inspection of the electrochemical sensor 100 performed when the electrochemical sensor 100 is installed in a house and the power is turned on. Here, for example, 25 minutes can be adopted as the predetermined period after the power is turned on.

As described above, the method of using the electrochemical sensor 100 of the present invention utilizes the characteristic characteristic of the electrochemical sensor 100 that when the inspection gas is blown, the positive current temporarily changes to the negative current. is there. In particular, it is possible to effectively suppress the occurrence of erroneous determination when high concentration H ₂ gas is sprayed as the inspection gas on the CO sensor as the electrochemical sensor 100 in the present embodiment.

  The present invention is such that the detection electrode to which the detection target gas reacts and the counter electrode to which oxygen reacts are connected to both sides of the electrolyte layer, and the detection target gas contained in the outside air contacts the detection electrode at a diffusion-controlled rate. An electrochemical sensor comprising a diffusion control means having a diffusion control hole for controlling the inflow amount of the outside air, and the current flowing from the counter electrode to the detection electrode via an external short circuit is positive current, The present invention can be applied to an alarm device including a determination unit that determines that the sensor has an abnormality when the negative current flows, with the current flowing in the direction being a negative current.

1 Electrolyte layer 2 Anode electrode (detection electrode)
3 Cathode electrode (counter electrode)
6 Diffusion control board (Diffusion control means)
6a Diffusion control hole 11 Sensor means 60 Alarm device 100 Electrochemical sensor 211b Determination means 212 Determination stop means 213 Power-on stop means

Claims (6)

Sensor means in which a detection electrode that reacts with the detection target gas and a counter electrode that reacts with oxygen are connected to both sides of the electrolyte layer, and the inflow of the outside air so that the detection target gas contained in the outside air contacts the detection electrode in a diffusion-controlled manner. An electrochemical sensor provided with a diffusion control means in which a diffusion control hole for controlling the amount is formed, a current flowing from the counter electrode to the detection electrode via an external short circuit is a positive current, and a current flowing in the opposite direction is a negative current As a method of using an electrochemical sensor in an alarm device provided with a determination means for determining that there is an abnormality in the sensor when the negative current flows,
After pre-Symbol plus current is detected, without determines that the negative current is abnormal when it is detected, determine the constant stopped for a predetermined time period, the use of an electrochemical sensor for stopping the determination by the determination means.   The method of using an electrochemical sensor according to claim 1, wherein when the electrochemical sensor is turned on, the determination by the determination means is stopped for a predetermined period after the power is turned on.   The method for using an electrochemical sensor according to claim 1 or 2, wherein the determination unit determines that the electrochemical sensor is abnormal when the negative current continues to flow for a predetermined determination period. Sensor means in which a detection electrode that reacts with the detection target gas and a counter electrode that reacts with oxygen are connected to both sides of the electrolyte layer, and the inflow of the outside air so that the detection target gas contained in the outside air contacts the detection electrode in a diffusion-controlled manner. And an electrochemical sensor provided with a diffusion control means having a diffusion control hole for controlling the amount,
An alarm provided with determination means for determining that the sensor has an abnormality when the negative current flows, with the current flowing from the counter electrode to the detection electrode via an external short circuit as a positive current and the current flowing in the opposite direction as a negative current. A device,
After pre-Symbol plus current is detected, without determines that the negative current is abnormal when it is detected, determine the constant stopped for a predetermined time period, the alarm device comprising a determination stop means for stopping the determination by the determination means.   5. The alarm device according to claim 4, further comprising a power-on stop unit that stops determination by the determination unit for a predetermined period after the power is turned on when the electrochemical sensor is turned on.   The alarm device according to claim 4 or 5, wherein the determination unit determines that the electrochemical sensor is abnormal when the negative current continues to flow for a predetermined determination period.

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