JP2942010B2 - Electrochemical gas sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical gas sensor and, more particularly, to a gas sensor for detecting gas in the atmosphere using an electrochemical reaction.

[0002]

2. Description of the Related Art As a basic structure of a gas sensor utilizing an electrochemical reaction, a plurality of electrodes are connected with an ion conductor, that is, an electrolyte to cause an electrochemical reaction. Conventionally, a liquid electrolyte or a gel electrolyte has been used as a material for the ion conductor. However, there has been a problem that the durability and reliability of the sensor are inferior due to liquid leakage and evaporation of the solvent. In order to solve such a problem, development of a gas sensor using an inorganic or organic solid electrolyte has been promoted.

[0003] Examples of inorganic solid electrolytes include β-alumina, NASICON, lithicon, and stabilized zirconia.
However, solid electrolytes made of these inorganic substances have high impedance at room temperature, so that ions are hardly conducted at room temperature. Therefore, in general, such an inorganic solid electrolyte as described above is heated and used in a state of low impedance, which means that the power consumption of the gas sensor increases, which is not preferable in practical use.

[0004] Examples of the organic solid electrolyte include polymers belonging to a cation exchange resin such as polystyrene sulfonate, polyvinyl sulfonate, perfluorosulfonate polymer, and pofluorocarboxylate polymer. Among these resins, perfluorosulfonate polymers are widely used as the most practically suitable ones. For example, Nafion (trade name: manufactured by DuPont)
There is something called.

[0005] The above-mentioned perfluorosulfonate polymer is preferred because the degree of dissociation of the cation is large, that is, the impedance is small, or it is relatively thermally and electrochemically stable. Further, since the perfluorosulfonate polymer is soluble in a solvent, a solid electrolyte layer made of the perfluorosulfonate polymer can be easily formed on an insulating substrate or an electrode by casting the solution. This means that the manufacture of the gas sensor is easy.

[0006]

In an electrochemical gas sensor using a perfluorosulfonate polymer as an electrolyte as described above, the physical property value of the perfluorosulfonate polymer changes with time, so that the sensitivity of the sensor increases with time. , And at a certain point in time, the function as a sensor can no longer be exhibited, resulting in a so-called service life. It is also important to extend the life of such an electrochemical gas sensor as much as possible, but there is a limit to extending the life. The conventional electrochemical gas sensor has a problem in that it is not easy to know that the gas sensor in use has reached the end of its life.

More specifically, physical properties such as impedance and gas permeability of a perfluorosulfonate polymer which is an electrolyte connecting the electrodes greatly affect the sensitivity of a gas sensor. Directly appears as a temporal change in sensor sensitivity. Then, when the sensor sensitivity decreases with time and becomes lower than the minimum value required for exhibiting the function as a sensor, the life of the sensor has expired at this point. It is extremely dangerous to continue using a gas sensor that has reached the end of its life, and it is required to know that the life has expired.

In a conventional gas sensor, a gas to be detected having a constant concentration is periodically injected, and the sensitivity of the sensor is measured to judge whether the sensor has sufficient sensitivity to function properly. However, the inspection work of the sensor by such a method requires much time and labor, and when the life of the sensor has expired during the inspection performed after a certain period of time, it cannot be known. However, this method is insufficient for quickly and reliably knowing the life of the sensor.

Therefore, an object of the present invention is to provide an electrochemical gas sensor as described above, which can extend the life thereof and at the same time, the sensor itself can be constantly operated without the troublesome work of the above-mentioned inspection work. It is an object of the present invention to provide an electrochemical gas sensor having a function of self-diagnosing the end of life by detecting sensitivity characteristics.

[0010]

According to the present invention, there is provided an electrochemical gas sensor according to the present invention, wherein a plurality of electrodes on an insulating substrate are connected by a solid electrolyte to perform a detecting action. A target gas detection unit for detecting a target gas to be detected and a reference gas detection unit for detecting a reference gas present at a certain concentration in the use environment. A life notifying means for outputting a signal when the output becomes equal to or less than a predetermined value is connected, and the target gas detection unit includes a working electrode, a counter electrode, a set of electrodes including a reference electrode, and a solid electrolyte covering over and between the electrodes. , And a protective film for protecting the solid electrolyte, wherein the reference gas detecting unit is a set of electrodes including a working electrode, a counter electrode, and a reference electrode. Thick solid electrolyte than the thickness of other portions thickness, and, a protective film for protecting the solid electrolyte.

First, the basic structure of the gas detector will be described. The electrodes are a set of a working electrode, a counter electrode, and a reference electrode, and are made of gold, platinum, or another electrode material, and are formed on an insulating substrate so as to have a shape and an arrangement corresponding to each function. . Then, a solid electrolyte layer is formed over and between these electrodes, and the electrodes are connected to each other by the solid electrolyte. In order to further reduce the aging of the solid electrolyte, a protective film made of a fluororesin or the like and covering the surface of the fixed electrolyte is formed. The specific material and manufacturing method of the protective film may be the same as those used in a conventional electrochemical gas sensor or the like.

According to the present invention, two gas detectors as described above are provided in one element. First, a target gas detection unit for detecting a target gas to be detected is provided. Gases to be detected are carbon monoxide, alcohol,
There are various gases such as hydrogen sulfide, and the voltage applied between the working electrode and the reference electrode is set according to the type of gas to be detected. Next, a reference gas detection unit for detecting a reference gas present at a certain concentration in the use environment is provided. As the reference gas, for example, when it is used in the atmosphere, oxygen is preferable. However, if the use environment is different, a reference gas corresponding to the environment may be selected. The reference gas detector sets the voltage applied between the working electrode and the reference electrode so that the above-described reference gas can be detected.

The target gas detecting section and the reference gas detecting section have substantially the same shape and structure. It is thicker than the part. In order to make the thickness of the solid electrolyte different from that on the working electrode, the working electrode and other electrodes are formed on a flat insulating substrate, and the solid electrolyte is thickened only on the working electrode. It may be formed with a step, or a step is formed on the insulating substrate so that only the working electrode formation point is lower than other parts, and the solid electrolyte is formed so that the top surface is flat. You may keep it. Further, steps may be formed on both the surface of the insulating substrate and the upper surface of the solid electrolyte.
The thickness of the solid electrolyte covering the working electrode of the reference gas detection unit must be large enough to prevent the reference gas from reaching the working electrode so that the reaction product accompanying the electrochemical reaction of the reference gas does not accumulate on the working electrode. It is necessary to set a certain amount of reference gas, which is necessary and required to obtain a certain detection output, so that it can reach the working electrode through the solid electrolyte. The specific thickness of the solid electrolyte varies depending on the structure and required performance of the entire sensor.

The target gas detector and the reference gas detector are connected to a power supply for applying a voltage to the target gas detector and the reference gas detector, and an output signal detected by the target gas detector, similarly to a normal gas sensor. A signal processing circuit for processing, an external circuit for displaying the detected concentration of the target gas, and issuing a signal or a warning when a target gas having a predetermined concentration or more is detected are connected.

Further, the reference gas detecting section is connected to a life notifying means. The life notifying means monitors the detection signal of the reference gas, and when the detection signal falls below a certain value, issues a warning signal or performs a warning display assuming that the gas sensor has reached the end of its life. Can announce the life of the device. As the service life notifying means, not only is it possible to notify the user of the service life by using a warning sound or warning lamp, etc., but also by sending a control signal to an external device or device incorporating a gas sensor to control the operation of the external device. Alternatively, operations such as replacement of the gas sensor can be automatically performed.

The life of the gas sensor is considered to be the life when the sensor sensitivity falls below a certain ratio, for example, when the sensor sensitivity becomes half of the initial value, or the sensor sensitivity decreases below a predetermined threshold value. The life of the gas sensor may be determined when the gas sensor is used. The value of the sensor sensitivity for determining that the life is reached can be freely set according to the use and purpose of the gas sensor.

[0017]

The electrochemical gas sensor detects the gas component by causing an electrochemical reaction at the interface between the working electrode and the electrolyte. Therefore, the reason why the sensor sensitivity decreases over time is that the time required for the gas component to reach the interface between the working electrode and the electrolyte decreases over time, and the reaction rate of the electrochemical reaction decreases over time. And the speed at which the product formed by the reaction moves to the counter electrode decreases over time. All of these phenomena follow a course determined by the configuration of the sensor. Therefore, by appropriately setting the configuration of the electrodes, the electrolyte, and the like of the reference gas detection unit, it is possible to form a reference gas detection unit having the same aging characteristics as the target gas detection unit.

As described above, by using the target gas detector and the reference gas detector having the same sensitivity over time,
The decrease in sensitivity over time in the target gas detector and the reference gas detector proceeds in the same manner. Therefore, if the detection output (sensitivity) of the reference gas detection unit with respect to the reference gas existing at a certain concentration in the use environment is continuously monitored,
It is possible to know the time-dependent decrease in the sensitivity of the reference gas detector. As described above, the decrease in sensitivity in the reference gas detection unit also indicates a decrease in sensitivity in the target gas detection unit. That is, when the sensor sensitivity of the reference gas detection unit falls below a certain ratio with respect to the initial value and becomes below a certain threshold value, the life notifying means connected to the reference gas detection unit is operated. For example, it is possible to notify that the life of the target gas detection unit, that is, the gas sensor has come to an end.

On the other hand, in order to extend the life of the sensor, it is effective to protect the solid electrolyte of the target gas detection section with a protective film made of a fluororesin or the like. This protective film is
It has functions such as preventing harmful substances from entering the solid electrolyte from the external environment, and conversely, stabilizing the characteristics of the solid electrolyte by preventing the moisture contained in the solid electrolyte from evaporating, As a result, the life of the sensor can be extended. However, if the solid electrolyte of the target gas detector is covered with a protective film, the solid electrolyte of the reference gas detector must also be covered with a protective film, and the reference gas detector will have the same aging characteristics as the target gas detector. I can't have it.

However, if the solid electrolytes of the target gas detector and the reference gas detector are covered with a protective film, even if the shapes of the protective films are completely the same, the temporal characteristics of the target gas detector and the reference gas detector are changed. However, there is a problem that the data is greatly different. The cause is considered as follows. The reference gas detector is in constant contact with the reference gas, which is always present at a constant concentration in the environment of use, so that the electrochemical reaction is constantly occurring on the working electrode, and the reaction products accompanying the electrochemical reaction are also generated. It will be constantly generated. For example, if the reference gas is oxygen, a reaction of O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O occurs on the working electrode of the reference gas detection unit, and water is continuously generated. When such a reaction product accumulates in the solid electrolyte, the sensitivity of the reference gas detection unit is affected. On the other hand, in the target gas detection unit, unless a target gas such as carbon monoxide is generated in the environment, no electrochemical reaction occurs on the working electrode, and, of course, no reaction product is generated.

That is, the sensitivity characteristics of the reference gas detector where the reaction product is always generated and the target gas detector where the reaction product is not always generated differ over time. However, if the surface of the solid electrolyte is exposed without being covered with the protective film, the reaction products generated by the reference gas detection unit are easily released into the environment from the surface of the solid electrolyte. Reaction products are less likely to accumulate in the section, and the difference in temporal characteristics between the target gas detection section and the reference gas detection section is relatively small.

However, if the surface of the solid electrolyte is covered with a protective film, the reaction products generated by the reference gas detection unit are difficult to be released into the environment from the solid electrolyte and accumulate in the solid electrolyte. is there. Therefore, when a protective film is used, it is very difficult to match the temporal characteristics of the reference gas detector with the temporal characteristics of the target gas detector. Therefore, in the present invention, the thickness of the solid electrolyte covering the working electrode of the reference gas detection unit is made larger than the thickness of the other parts, so that the reaction product is accumulated at the working electrode of the reference gas detection unit. prevent. That is, if the solid electrolyte covering the working electrode of the reference gas detection unit is thick, the amount of the reference gas that reaches the working electrode through the solid electrolyte from the environment decreases,
The formation of the electrochemical reaction and reaction products on the working electrode is also reduced. As a result, the sensitivity of the reference gas detection unit does not change, and the same aging characteristics as the target gas detection unit can be maintained. Moreover, even if the thickness of the solid electrolyte is large, a small amount of the reference gas reaches the working electrode, so the reference gas detection unit should always output the detection signal of the reference gas and monitor its change over time. Is possible. Also, the difference in the thickness of the solid electrolyte covering the working electrode of the reference gas detection unit and the working electrode of the target gas detection unit means that there is a structural difference between the reference gas detection unit and the target gas detection unit. However, this has little effect on the aging characteristics of sensitivity. In addition, since the difference in the sensitivity characteristics based on the difference in the thickness of the solid electrolyte can be known in advance at the time of manufacturing the sensor, if appropriate sensitivity correction is performed, the time-dependent characteristics of the reference gas detection unit can be changed to the target gas. It is easy to match with the aging characteristics of the detection unit.

As described above, in the electrochemical gas sensor according to the present invention, by extending the life or improving the performance by forming the protective film,
By setting the thickness of the solid electrolyte on the working electrode of the reference gas detector as described above, it is possible to prevent the sensitivity characteristics of the target gas detector and the reference gas detector from changing with time.

[0024]

Next, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 3 show a schematic structure of an electrochemical gas sensor according to the present invention. First, the surface of an insulating substrate 10 made of a silicon substrate or the like having an insulating film formed on the surface is substantially flat as a whole, and as is apparent from FIG. There is a step between the parts. On the surface of such an insulating substrate 10, two sets of electrodes made of platinum, gold or other electrode materials are formed. That is, the working electrode 2 for detecting the detection target gas
0, a counter electrode 30, and a target gas detection electrode set including three rectangular electrodes of a reference electrode 40, and a working electrode 50 for detecting a reference gas, which is disposed symmetrically facing the electrode set, This is a reference gas detection electrode set including three rectangular electrodes of a counter electrode 60 and a reference electrode 70. The working electrode 50 for detecting the reference gas is formed in the lower portion 12 of the insulating substrate 10. For the formation of each electrode, ordinary electrode forming means such as sputtering or vapor deposition is used.

The two sets of electrodes 20 to 40 and 50 to 70 are covered with solid electrolyte layers 80 and 82 made of perfluorosulfonate polymer or the like on and between the electrodes.
Are formed separately for the reference gas detection and the target gas detection. Solid electrolyte layers 80, 82
Is formed flat. Therefore, as shown in FIG. 2, the thickness T ₁ of the solid electrolyte layer 82 on the working electrode 50 for detecting the reference gas is larger than the thickness T ₀ of the solid electrolyte layer 82 in the other portions. It is thicker by the step. The materials and forming means of the solid electrolyte layers 80 and 82 may be the same as those of a normal gas sensor.

Then, the solid electrolyte layer 80 as described above,
Protective films 90 and 92 made of a fluorine-based resin are formed so as to cover the entire surface of 82. In FIG. 1, the protective film 90,
92 are indicated by hatching. Protective film 9
0 and 92 are evaporation method, plasma polymerization method , casting
It is formed by a method or the like. One end of each of the electrodes 20 to 70 is extended to the outside of the solid electrolyte layers 80 and 82 and the protective films 90 and 92 and is exposed to the outside, and the connection terminal portions 22, 32, 42, 52, 62 and 72.
In this way, the target gas detection unit A and the reference gas detection unit B are provided side by side on one insulating substrate 10.

Each of the electrodes 20 to 40 of the target gas detector A is
It is connected to the signal processing circuit 100 via a lead wire 102 connected to the terminal portions 22 to 42, so that the detection signal of the target gas detected by the target gas detection unit A can be taken out and used. Has become. Reference gas detector B
Each of the electrodes 50 to 70 is connected to the life notifying means 110 via a lead wire 104 connected to the terminal portions 52 to 72.

The life notifying means 110 includes a reference gas detector B
The sensor outputs a signal when the detection output falls below a certain value, emits a warning sound or turns on a warning lamp, so that the sensor can be notified that the sensor has reached its end of life. Has become. The life notifying unit 110 having such a function is configured by a normal electronic circuit or the like similar to that used in various devices.

The operation of the gas sensor having the above-described structure in the target gas detector A will be described. The gas component of the detection target gas passes through the protective film 90 and the solid electrolyte layer 80 from the surface of the protective film 90 and reaches the working electrode 20, where an electrochemical reaction occurs. Counter electrode 3
At 0, a reaction occurs that pairs with the working electrode 20. As a result, a detection current flows between the working electrode 20 and the counter electrode 30,
Detection and quantification of gas components can be performed. The reference electrode 40 functions as a reference for maintaining the potential of the working electrode 20 constant. That is, by maintaining the potential of the working electrode 20 at a constant potential corresponding to the gas component to be detected, the gas component to be detected causes an electrochemical reaction at the working electrode 20. Such a sensor operation is the same as that of a normal electrochemical gas sensor.

Next, the life detecting operation of the reference gas detecting section B will be described. In the reference gas detector B, oxygen as a reference gas is supplied from the surface of the protective film 92 to the protective film 92.
Then, the light passes through the solid electrolyte layer 82 and reaches the working electrode 50, where an electrochemical reaction occurs. However, since the thickness T ₁ of the solid electrolyte layer 82 above the working electrode 50 is large, the amount of oxygen reaching the working electrode 50 is small, and the reaction amount is extremely small. At the counter electrode 60, a reaction that forms a pair with the working electrode 50 occurs, and an oxygen detection current flows between the working electrode 50 and the counter electrode 60. In this reference gas detecting section B, the working electrode 5
Since the zero potential is maintained at a constant potential corresponding to oxygen with reference to the reference electrode 70, oxygen can be detected. That is, the reference gas detector B and the target gas detector A
However, only the potential setting of the working electrodes 20 and 50 is different, and the basic electrochemical reaction and the principle of the flow of the detection current are the same.

Since oxygen is always present in the atmosphere at a constant concentration, a constant detection current should always be obtained in the reference gas detector B unless the sensitivity changes over time. However, as described above, since the sensitivity of the reference gas detection unit B decreases with time, the detection current gradually decreases. The same phenomenon as the change in the detection current, that is, the sensitivity with time, in the reference gas detection unit B occurs simultaneously in the target gas detection unit A. Therefore, the reference gas detector B
, The detection current (sensitivity) is constantly monitored, and if the detection current becomes equal to or less than a predetermined value, it may be determined that the life of the sensor, that is, the target gas detection unit A is reached.

Next, the results of manufacturing an electrochemical gas sensor having the above-described structure and testing its gas detecting action over time will be described. Example 1 As a material of the insulating substrate 10, a 10 mm square silicon substrate having a thickness of 1 mm was used. Of the surface of the silicon substrate, only a part 12 has a step lower than the other part by 0.1 mm, and the whole surface is oxidized. Further, in order to increase the adhesion between the substrate and the electrode, a polysilicon layer having a thickness of about 2000 mm was formed on the surface of the silicon substrate by sputtering. On the insulating substrate 10, working electrodes 20 and 50 made of platinum by sputtering and a counter electrode 3
Reference electrodes 40 and 70 made of 0, 60 and gold were formed. However, the working electrode 50 was formed on a portion 12 of the surface of the insulating substrate 10 which was lower than other portions.
Thereafter, 5% by weight of perfluorosulfonate polymer was added.
The solution was cast on each of the electrodes 20 to 40, 50 to 70 and the insulating substrate 10 around the electrodes to form solid electrolyte layers 80 and 82 made of a perfluorosulfonate polymer having a thickness of 3 μm. Since the upper surfaces of the solid electrolyte layers 80 and 82 are flat, the solid electrolyte layer 82 having a thickness of about 0.1 mm covers the working electrode 50 formed on the lower portion 12 of the insulating substrate 10. Become. Further, the protective film 9 made of a polymer of tetrafluoroethylene covers the entire surface of the solid electrolyte layers 80 and 82.
0,92 were formed by plasma polymerization.

In order to confirm that the gas sensor combined with the target gas detection section A and the reference gas detection section B thus manufactured has a sensor function for the target gas and a function of notifying the life, Gas detector A
The time-dependent changes in the sensitivity to carbon monoxide and oxygen of the reference gas detector B and the reference gas detector B were measured. The test apparatus shown in FIG. 4 was used for the measurement. A gas sensor is accommodated in the measurement chamber 120, and the terminal portions 22 of the electrodes 20 are connected via lead wires 121 to respective potentiostats 122, 1 and 1 for the target gas detection unit A and the reference gas detection unit B.
23. Recorders 124 and 125 are connected to the potentiostats 122 and 123 for the target gas detection unit A and the reference gas detection unit B, respectively.

Using the test apparatus as described above, the working electrode 20 and the reference electrode 40 of the target gas detector A for detecting carbon monoxide are used.
The test was performed by setting the applied voltage between the electrodes to 0.45 V and setting the applied voltage between the working electrode 50 and the reference electrode 70 of the reference gas detector B for detecting oxygen to -0.6 V. The oxygen detection current flowing between the working electrode 50 and the counter electrode 60 of the reference gas detection unit B was constantly monitored by the recorder 125. Also,
The atmosphere in the chamber 120 is replaced with air containing 1000 ppm of carbon monoxide from the state of only air, and the carbon monoxide detection current flowing between the working electrode 20 and the counter electrode 30 of the target gas detection part A at this time is recorded by the recorder 124. It was measured. Air containing carbon monoxide was supplied into the chamber 120 at regular intervals to repeat the measurement.

FIG. 5 shows the measurement results. As is clear from this graph, the time-dependent changes in the sensitivity of the target gas detector A to carbon monoxide and the sensitivity of the reference gas detector B to oxygen show almost the same tendency. Therefore, assuming that the time until the target gas detecting unit A becomes a sensitivity at which the function of the target gas detecting unit A can no longer function as a sensor is life, the sensitivity of the reference gas detecting unit B is equal to or less than the sensitivity in the elapsed time corresponding to the life of the target gas detecting unit B. At this point, if the life of the sensor is determined to be appropriate and an appropriate warning signal is issued, the life of the sensor can be detected quickly and reliably.

Example 2 A gas sensor was manufactured through the same manufacturing process as in Example 1 except that Teflon was used as a material for the protective films 90 and 92 and a vapor deposition method was used as a method for forming the same. Manufactured. The same measurement as in Example 1 was performed on the gas sensor manufactured as described above. FIG. 6 shows the measurement results. In the case of the second embodiment, compared to the first embodiment,
Although the sensitivity deterioration rate is large, the behavior of the sensitivity of the target gas detection unit A and the reference gas detection unit B with respect to the change with time is the same. In the case of this gas sensor as well, the detection output of the It can be seen that the life can be detected.

[0037]

According to the above-described electrochemical gas sensor according to the present invention, in addition to a target gas detecting section similar to a normal gas sensor, a reference gas present at a constant concentration in a use environment is detected. With the provision of the reference gas detection unit, the life of the gas sensor can be quickly and reliably detected. That is, the gas sensor itself has a function of performing a self-diagnosis as to whether the life has expired. As a result, a large amount of labor and time required for inspection work for checking the function of the sensor can be saved, and the cost for maintenance can be significantly reduced. In addition, it is possible to provide a highly reliable gas sensor that can reliably avoid a dangerous situation that occurs when a gas sensor whose life has expired is used as it is.

In particular, by providing the protective layer for protecting the solid electrolyte, it is possible to prevent the sensitivity of the sensor from deteriorating due to a change in physical properties of the solid electrolyte layer with time, and to extend the life of the sensor. Furthermore, since the thickness of the solid electrolyte layer is thicker than the other portions on the working electrode of the reference gas detection unit, even if the above-described protective layer is formed, a reaction product accompanying the electrochemical reaction of the reference gas is formed. Is less likely to accumulate on the working electrode, and the temporal characteristics of the reference gas detector can be made to exactly match the temporal characteristics of the target gas detector, so that the life notification function of the reference gas detector can be satisfactorily exhibited.

As a result of the above, the electrochemical gas sensor according to the present invention can satisfy all of the conflicting demands, which have been impossible to realize conventionally, such as longer life and quick and reliable notification of the life. This can greatly contribute to improving the functions of various kinds of gas sensors or expanding the applications.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a gas sensor showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a reference gas detection unit.

FIG. 3 is an enlarged cross-sectional view of a target gas detection unit.

FIG. 4 is a schematic configuration diagram of a test apparatus for sensor sensitivity.

FIG. 5 is a diagram showing sensitivity measurement results.

FIG. 6 is a diagram showing sensitivity measurement results of another example.

[Explanation of symbols]

 Reference Signs List A Target gas detection unit B Reference gas detection unit 10 Insulating substrate 12 Low part 20, 50 Working electrode 30, 60 Counter electrode 40, 70 Reference electrode 80, 82 Solid electrolyte 90, 92 Protective film 110 Life notification means

Claims (1)

(57) [Claims] 1. An electrochemical gas sensor for detecting a target gas by connecting a plurality of electrodes on an insulating substrate with a solid electrolyte and using the target gas detection unit for detecting a target gas to be detected on the same substrate. A reference gas detection unit for detecting a reference gas present at a constant concentration in the environment is provided, and the reference gas detection unit is connected to a life notification unit that emits a signal when the detection output becomes a certain value or less, The target gas detection unit is a working electrode, a counter electrode, a set of electrodes consisting of a reference electrode, a solid electrolyte covering on and between each electrode, and
The reference gas detector comprises a set of electrodes consisting of a working electrode, a counter electrode, and a reference electrode. An electrochemical gas sensor comprising: a solid electrolyte having a thickness greater than a thickness of the solid electrolyte; and a protective film for protecting the solid electrolyte.