JP4800908B2 - Gas alarm with built-in electrochemical gas sensor - Google Patents

Description

  The present invention relates to a gas alarm device incorporating an electrochemical gas sensor using a proton conductor film.

  2. Description of the Related Art Conventionally, as a CO alarm device for detecting and alarming CO gas due to incomplete combustion or the like of a combustion device, a device incorporating an electrochemical CO sensor is known.

  As shown in a cross-sectional view in FIG. 7, this electrochemical CO sensor 1A has a proton conductor film 3 installed in an upper opening 4 of a resin container 2A in which water 5 is housed, and a counter electrode 32 is provided. While being exposed in the container 2A, a resin cap 8A incorporating a gas adsorption filter 8c is overlapped on the opposite detection electrode 31 and caulked and fixed to the upper opening 4 of the container 2A.

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

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

Therefore, when a load (not shown) is connected between the detection electrode 31 and the counter electrode 32, a flow of electrons (2e ⁻ ) staying in the detection electrode 31 toward the counter electrode 32 is generated in the load, thereby causing the load from the counter electrode 32 to load. Since a short-circuit current flows toward the detection electrode 31 via the current, a current-voltage conversion is performed on the short-circuit current flowing through the load to obtain a CO concentration signal having a voltage value corresponding to the CO concentration in the surrounding atmosphere (for example, Patent Documents 1 and 2).

The electrochemical CO sensor 1A having such a detection principle configuration itself generates a short-circuit current having a magnitude corresponding to the CO concentration in the ambient atmosphere, which is a source of the CO concentration signal. Since it does not require power supply, it is suitable for use in a CO alarm device that needs to be driven by a battery for a long period of time.
JP 2004-170101 A JP 2004-279293 A

By the way, in the above-described electrochemical CO sensor 1A, the number of electrons (2e ⁻ ) generated at the detection electrode 31 is small, and the CO concentration signal corresponding to the CO concentration in the surrounding atmosphere is very weak. When radio waves exist in the vicinity, high-frequency induced currents flow superimposed on the line where the short-circuit current flows, and the waveform of the CO concentration signal generated by current-voltage conversion from the short-circuit current after superposition is disturbed. As a result, the CO concentration detection accuracy is lowered.

  Therefore, in a battery-type CO alarm device that monitors and alerts the CO concentration using the electrochemical CO sensor 1A, eliminating the influence of surrounding radio waves on the electrochemical CO sensor 1A reduces the CO concentration in the ambient atmosphere. It is important for accurately grasping and, therefore, accurately outputting an alarm regarding CO concentration.

  The above-described problems cannot be generated only in the CO alarm device, but are large depending on the concentration of the target gas in the ambient atmosphere generated between the detection electrode and the counter electrode of the electrochemical gas sensor. This current can occur widely when the concentration of the target gas in the ambient atmosphere is measured by the signal processing circuit using the gas concentration signal of the voltage value.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to accurately grasp the concentration of the target gas in the surrounding atmosphere using the built-in electrochemical gas sensor even when radio waves exist in the vicinity. Thus, an object of the present invention is to provide a gas alarm device that can accurately output an alarm regarding the concentration of the target gas.

In order to achieve the above object, the gas alarm with a built-in electrochemical gas sensor according to claim 1 of the present invention is generated at a detection electrode of a proton conductor film fixed to an upper opening of a container in which water is contained. Due to the oxidation reaction of the target gas existing in the ambient atmosphere of the container and the reduction reaction of the proton generated by the oxidation reaction generated at the counter electrode of the proton conductor film, the target gas in the ambient atmosphere of the container An electrochemical gas sensor that generates a current having a magnitude corresponding to the concentration between the detection electrode and the counter electrode, and the current connected to the detection electrode and the counter electrode is used to supply the current to the target gas in the ambient atmosphere of the container. A signal processing circuit that converts the gas concentration signal to a voltage value corresponding to the concentration is built in the case, and the concentration of the target gas in the ambient atmosphere of the container indicated by the gas concentration signal is an alarm. A gas detector for outputting an alarm when it reaches the level, the container is constituted by a metal can serving also as a metal shield member for covering the container, wherein the counter electrode to the metal can is electrically connected The terminal on the counter electrode side is constituted by the metal can, and the metal can is connected to a ground potential portion of the signal processing circuit via a capacitor .

The gas alarm with a built-in electrochemical gas sensor according to claim 2 is the gas alarm with a built-in electrochemical gas sensor according to claim 1 , wherein the concentration of the target gas in the ambient atmosphere of the metal can is measured. A switch that can be switched from an open state to a closed state between the metal can and the signal processing circuit, and the signal processing is performed between the switch and the metal can via the capacitor. It was assumed that it was connected to the ground potential location of the circuit.

In order to achieve the above object, the gas alarm with a built-in electrochemical gas sensor according to claim 3 of the present invention is generated at a detection electrode of a proton conductor film fixed to an upper opening of a container in which water is contained. Due to the oxidation reaction of the target gas existing in the ambient atmosphere of the container and the reduction reaction of the proton generated by the oxidation reaction generated at the counter electrode of the proton conductor film, the target gas in the ambient atmosphere of the container An electrochemical gas sensor that generates a current having a magnitude corresponding to the concentration between the detection electrode and the counter electrode, and the current connected to the detection electrode and the counter electrode is used to supply the current to the target gas in the ambient atmosphere of the container. A signal processing circuit that converts the gas concentration signal to a voltage value corresponding to the concentration is built in the case, and the concentration of the target gas in the ambient atmosphere of the container indicated by the gas concentration signal is an alarm. A gas alarm device for outputting an alarm when reaching a bell, a metal shield member disposed between the case and the container to cover the container and to which the counter electrode is electrically connected; and the metal shield A metal member interposed between the shield member and the case so as to face the member and grounded, and an insulating member interposed so as to insulate between the metal shield member and the metal member. It is characterized by that.

  According to the gas alarm with a built-in electrochemical gas sensor according to the first aspect of the present invention, when radio waves are present around the gas alarm, an induced current flows on a line connecting the detection electrode or counter electrode and the signal processing circuit. Therefore, the waveform of the gas concentration signal obtained by current-voltage conversion is disturbed in the current of a magnitude corresponding to the gas concentration in the ambient atmosphere of the container generated between the detection electrode and the counter electrode. This causes an erroneous output of an alarm output when the concentration of the target gas in the atmosphere around the container indicated by the gas concentration signal reaches an alarm level.

  However, the radio wave is blocked by a metal shield member that is disposed between the case and the container and covers the container, and the high frequency induced current caused by the radio wave passes through the capacitor from the metal shield member to the signal processing circuit that is the connection destination. On the other hand, the current generated between the detection electrode and the counter electrode according to the gas concentration in the ambient atmosphere of the container is direct current and does not pass through the capacitor, so the induction current due to radio waves is not superimposed By extracting a gas concentration signal having a correct waveform, it is possible to accurately grasp the concentration of the target gas in the surrounding atmosphere, and thus to accurately output an alarm regarding the concentration of the target gas.

In addition, a metal can which is electrically connected to the counter electrode of the proton conductor film and constitutes a terminal on the counter electrode side also serves as a metal shield member to form a container, and the signal processing circuit 20 is grounded via the capacitor C. Since it is connected to the potential location, the metal can functioning as a terminal on the counter electrode side can be used as it is as a metal shield member for blocking radio waves, thereby improving the efficiency of the configuration.

Further, according to the gas alarm with a built-in electrochemical gas sensor of the present invention described in claim 2 , in the gas alarm with a built-in electrochemical gas sensor of the present invention described in claim 1 , the target gas in the ambient atmosphere of the metal can When the concentration is not measured, the electrochemical gas sensor side is connected to the ground potential portion of the signal processing circuit via a capacitor rather than the switch for disconnecting the signal processing circuit side from which the power supply is cut off during the concentration measurement.

  For this reason, even when the concentration of the target gas is not measured when the switch is open, a high-frequency induced current generated by radio waves existing around the metal can is passed to the ground potential location of the signal processing circuit. So that it does not flow to the signal processing circuit side when the switch is closed.

According to the gas alarm with a built-in electrochemical gas sensor of the present invention described in claim 3 , the radio wave is blocked by the metal shield member disposed between the case and the container and covering the container, and the metal shield member and the metal member By providing an insulating member between the metal shield member and the metal member, capacitance is formed between the metal shield member and the metal member. On the other hand, the current generated between the detection electrode and the counter electrode according to the gas concentration in the atmosphere around the container is direct current and does not flow from the metal shield member to the metal member. Since noise countermeasures can be taken, the correct concentration of the gas concentration signal with no superimposed induction current due to radio waves is taken out to accurately grasp the concentration of the target gas in the surrounding atmosphere. Hence, it is possible to allow precisely the output of the alarm on the concentration of the target gas. Furthermore, since noise countermeasures can be taken without using a capacitor, it is effective when the electrochemical sensor is a thin box shape or when the wiring board is a flexible wiring board.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of an electrochemical CO sensor built-in CO alarm device employing an electrochemical gas sensor built-in gas alarm device according to an embodiment of the present invention. The electrochemical CO of this embodiment indicated by reference numeral 100 in FIG. The sensor built-in CO alarm device (corresponding to the gas sensor built-in gas alarm device in the claims, hereinafter abbreviated as “CO alarm device”) is attached in advance to a wall surface (not shown) of the installation destination. The resin case 110 is suspended from the hook 210 for use.

  Inside the case 110, there is an electrochemical CO sensor 1 shown in a sectional view in FIG. 2, a battery B, a constant voltage circuit 10, a signal processing circuit 20, and a base voltage generating circuit shown in a circuit diagram of an electrical configuration in FIG. 30, first and second switch circuits IC1 and IC2, a power switch SW, a microcomputer (hereinafter abbreviated as “μCOM”) 40, an audio IC 50, an indicator 60, a speaker 70, and a capacitor C are incorporated. .

  Among these, the electrochemical CO sensor 1 of the present embodiment shown in FIG. 2 includes a container 2A, a diffusion prevention plate 7A, and a cap 8A of the electrochemical CO sensor 1A of FIG. (Corresponding to the container in the claims) is different from the electrochemical CO sensor 1A in FIG. 7 in that the metal diffusion prevention plate 7 and the metal cap 8 are changed. The operation principle is the same as that of the electrochemical CO sensor 1A of FIG.

  For this reason, in the electrochemical CO sensor 1 of the present embodiment, the metal can 2 electrically connected to the counter electrode 32 of the proton conductor film 3 via the diffusion prevention plate 7 functions as a terminal on the counter electrode 32 side. The metal cap 8 that contacts the detection electrode 31 of the proton conductor film 3 functions as a terminal on the detection electrode 31 side.

  Therefore, when a load (not shown) is connected between the metal cap 8 which is the terminal on the detection electrode 31 side and the metal can 2 which is the terminal on the counter electrode 32 side, the electrons (2e−) accumulated in the detection electrode 31 are removed. Since a flow toward the counter electrode 32 is generated in the load, and a short-circuit current flows from the counter electrode 32 through the load to the detection electrode 31, current-voltage conversion is performed on the short-circuit current flowing through the load in the ambient atmosphere. A CO concentration signal having a voltage value corresponding to the CO concentration is obtained.

  The constant voltage circuit 10 shown in FIG. 3 is for making the voltage of the battery B constant, and the signal processing circuit 20 is connected between the metal cap 8 and the metal can 2 of the electrochemical CO sensor 1. Thus, the short-circuit current from the counter electrode 32 of the proton conductor film 3 to the metal cap 8 to the detection electrode 31 through the metal can 2 and the signal processing circuit 20 is converted into a voltage, amplified, and the CO concentration (the target gas in the claims) It is output as a CO concentration signal (corresponding to a gas concentration signal in claims) of a voltage corresponding to the concentration).

  The base voltage generation circuit 30 generates a base voltage that determines a gain at the time of amplification of the CO concentration signal in the signal processing circuit 20, a metal cap 8 that is a terminal on the detection electrode 31 side of the proton conductor film 3, and a signal processing circuit. 20 to be supplied.

  The signal processing circuit 20 and the base voltage generation circuit 30 apply the constant voltage from the constant voltage circuit 10 while the power switch SW is turned on when measuring the CO concentration in the ambient atmosphere of the CO alarm device 1. A base that operates as a power source and determines the gain of an amplifier (not shown) in the signal processing circuit 20 that the base voltage generation circuit 30 outputs to the metal cap 8 of the electrochemical CO sensor 1 and the signal processing circuit 20. The voltage (reference voltage) is, for example, 2.7 V generated from the constant voltage power source supplied from the constant voltage circuit 10 when measuring the CO concentration when the power switch SW is ON, and the power switch SW is turned OFF. When the CO concentration is not measured, the constant voltage power supply is not supplied from the constant voltage circuit 10, and therefore it becomes 0V.

  The first switch circuit IC1 is short-circuited between the metal cap 8 that is the terminal on the detection electrode 31 side and the metal can 2 that is the terminal on the counter electrode 32 side when the power switch SW is OFF and the CO concentration is not measured. The second switch circuit IC2 (corresponding to the switch in the claims) disconnects the electrochemical CO sensor 1 from the signal processing circuit 20 when the CO concentration when the power switch SW is OFF is not measured. is there.

  The first switch circuit IC1 is always operated by receiving a constant voltage power supply from the constant voltage circuit 10 regardless of whether the power switch SW is turned on or off, and the second switch circuit IC2 is operated by the CO alarm device 1. The constant voltage from the constant voltage circuit 10 is operated as a power source while the power switch SW that is turned on when measuring the CO concentration in the ambient atmosphere is turned on.

  The μCOM 40 is always operated by receiving a constant voltage power supply from the constant voltage circuit 10 regardless of whether the power switch SW is turned on or off. The μCOM 40 is operated by the power switch SW and the first and second switch circuits IC1 and IC2. While controlling ON and OFF, based on the CO concentration signal input from the signal processing circuit 20, it is determined whether or not the CO concentration in the ambient atmosphere of the CO alarm device 1 has reached the alarm level. In addition, the indicator 60 is turned on, and a voice message such as “Pippippo is dangerous because the air is dirty. Open the window and ventilate” is read from the voice IC 50 and sounded by the speaker 70 (voice output). Let

  Incidentally, the negative side of the battery B, the constant voltage circuit 10, the signal processing circuit 20, the base voltage generation circuit 30, the first and second switch circuits IC1 and IC2, and the μCOM 40 are all grounded (0 V).

  The positive side of the capacitor C is connected to the metal can 2 which is a terminal on the counter electrode 32 side of the proton conductor film 3, and the negative side is grounded (0V).

  In the CO alarm device 100 having such a configuration, when a radio wave is present in the vicinity, a high-frequency induced current flows through the metal can 2 of the electrochemical CO sensor 1, and the CO concentration at which the power switch SW is turned on is measured. Sometimes a high-frequency induced current is superimposed on the short-circuit current flowing from the metal can 2 to the metal cap 8 via the signal processing circuit 20 and having a magnitude corresponding to the CO concentration in the ambient atmosphere.

  However, the high-frequency induced current component that can pass through the capacitor C flows to the capacitor C side rather than the signal processing circuit 20 side having a high impedance, and therefore flows to the signal processing circuit 20 side according to the CO concentration in the ambient atmosphere. Only the short-circuit current component of the magnitude is obtained.

  Therefore, the waveform of the CO concentration signal obtained by current-voltage conversion and amplification of the current flowing through the signal processing circuit 20 is not disturbed, and the CO concentration is detected accurately, and the CO concentration in the ambient atmosphere has reached the alarm level. The alarm display and ringing by the indicator 60 and the speaker 70 can be accurately performed.

  Note that the connection side on the + side of the capacitor C is closed between the signal processing circuit 20 and the first switch circuit IC1 that is closed when the CO concentration is measured and connects the signal processing circuit 20 to the electrochemical CO sensor 1, for example. There may be.

  However, the second switch circuit IC2 is in an open state by connecting the + side of the capacitor C between the second switch circuit IC2 and the metal can 2 of the electrochemical CO sensor 1 as in the present embodiment. Even when the CO concentration is not measured, the metal can 2 that is the terminal on the counter electrode 32 side is connected to the + side of the capacitor C, and the induced current generated in the metal can 2 is connected to the ground potential (0 V). This is advantageous because it can be prevented from flowing to the signal processing circuit 20 when the second switch circuit IC2 is turned on.

  Further, the metal shield member for blocking the electrochemical CO sensor 1 from the radio waves generated in the vicinity is not a metal can 2 used as a container for containing water 5 as in the present embodiment, but a container for non-metallic water 5. (For example, the container 2A in FIG. 7) and a dedicated metal shield member that covers the water 5 container disposed between the case 110 of the CO alarm device 100 may be used, or the case 110 itself may be made of a metal material. It may be configured to function as a metal shield member.

  In this case, the container for water 5 is made of non-metal, and the metal shield member is insulated from the counter electrode 32 through the container. Therefore, a capacitor C for DC insulation is interposed when the metal shield member is grounded (0 V). There is no need.

  However, if the metal can 2 used as a container for containing the water 5 is used as a metal shield member as in the present embodiment, a DC conductor C need to be interposed, but the proton conductor film The metal can 2 used as the terminal of the counter electrode 3 can be used as it is as a metal shield member for blocking radio waves, and as a result, the efficiency can be improved by simplifying the configuration, which is advantageous.

  Furthermore, the water accommodated inside the container such as the metal can 2 may be in a gel form.

  Next, in Example 2, an embodiment in which noise countermeasures are performed without using the capacitor C described above will be described. Since the basic configuration is the same as that of the first embodiment, the same or corresponding parts as those described in the first embodiment are denoted by the same reference numerals and detailed description thereof is omitted, and only different parts are described below. explain.

  An electrochemical CO sensor built-in CO alarm device (corresponding to the gas sensor built-in gas alarm device in the claims, hereinafter abbreviated as “CO alarm device”) 100 according to the second embodiment shown in FIG. As described above, the electrochemical CO sensor 1 shown in FIG. 2, the battery B, the constant voltage circuit 10, the signal processing circuit 20, the base voltage generation circuit 30, the first and second switch circuits IC1, IC2 shown in FIG. , A wiring board 120 provided with a power switch SW, μCOM 40, audio IC 50, indicator 60, speaker 70, etc., and an insulating member 140 interposed between the electrochemical CO sensor 1 and the wiring board 120 are incorporated. . The difference from the first embodiment is that the noise reducing capacitor C is deleted from the circuit configuration shown in FIG.

  In the electrochemical CO sensor 1, as in Example 1, the metal can 2 electrically connected to the counter electrode 32 of the proton conductor film 3 via the diffusion prevention plate 7 functions as a terminal on the counter electrode 32 side. The metal cap 8 that contacts the detection electrode 31 of the proton conductor film 3 functions as a terminal on the detection electrode 31 side. That is, the metal can 2 functions as a metal shield member in the claims, and the metal can 2 also serves as a container in the claims.

  As shown in FIGS. 4 to 6, the wiring board 120 has terminals 121 and 122 implanted therein, and functions as a detection electrode 31 and a counter electrode 32, respectively. The electrochemical CO sensor 1 is positioned and fixed so as to face one surface of the wiring board 120 by the terminals 121 and 122.

  The wiring board 120 has a GND solid pattern 130 such as a copper foil formed on the surface facing the electrochemical CO sensor 1, and the GND solid pattern is interposed between the case 110 and the ground of the signal processing circuit 20. It is connected to a potential location. That is, in the second embodiment, since the GND solid pattern 130 functions as a metal member in the claims, the GND solid pattern 130 is formed to have substantially the same shape as the outer shape of the electrochemical CO sensor 1. It is preferable.

  In the second embodiment, the case where the metal member in the claims is the GND solid pattern 130 of the wiring board 120 will be described. However, the present invention is not limited to this. For example, the metal plate or the like can be a metal can. 2 may be assembled in the case 110 so as to face 2 and the metal plate or the like is grounded.

  The insulating member 140 is an insulating sheet or the like that insulates the metal can 2 and the GND solid pattern 130 from each other, that is, functions as a dielectric. In this embodiment, the insulating member 140 is attached to the wiring board 120 so that the insulating member 140 covers the GND solid pattern 130. As the insulating member 140, various members can be used as long as they can insulate the metal can 2 and the GND solid pattern 130, such as being formed as a resist film on the surface of the wiring board.

  The electrochemical CO sensor 1 is mounted on the wiring board 120 so as to face the GND solid pattern 130 of the wiring board 120 and have the insulating member 130 interposed therebetween. That is, in the case 110 of the electrochemical CO sensor 1, the insulating member 140 functions as a dielectric, so that a capacitance can be formed between the metal can 2 and the GND solid pattern 13.

  As is apparent from the above description, the CO alarm device 100 includes the metal can 2 corresponding to the metal shield member, the GND solid pattern 130 corresponding to the metal member, and the insulating member 140. In the above-described first embodiment, the case where the electrochemical CO sensor 1 has a cylindrical shape has been described. However, in the second embodiment, a thin box shape or the like is formed, and the GND solid pattern 130 of the wiring board 120 is formed. The outer shape of the electrochemical CO sensor 1 is preferably a thin box shape so that the opposing surface areas are increased.

  According to the CO alarm device 100 according to the second embodiment, radio waves are blocked by the metal can 2 that forms the container of the electrochemical CO sensor 1 that is a metal shield member, and the metal can 2 and the metal member. Since the electrostatic member is formed between the metal can 2 and the GND solid pattern 130 by providing the insulating member 140 between the GND solid pattern 130, the high-frequency induced current caused by the radio wave is generated by the metal can 2 and the GND solid pattern. The current generated between the detection electrode 31 and the counter electrode 32 according to the gas concentration in the ambient atmosphere of the metal can 2 flows from the metal can 2 to the ground potential location of the signal processing circuit 20 from the DC, and the GND solid Since it does not flow into the pattern 130, that is, noise countermeasures using the stray capacitance on the structure can be taken, the gas concentration of the correct waveform on which the induction current due to radio waves is not superimposed Remove the items, the concentration of the target gas in the surrounding atmosphere accurately grasped, and thus, the output of the alarm on the concentration of the target gas can be made to perform accurately. Furthermore, since noise countermeasures can be taken without using the capacitor C of Example 1, it is effective when the electrochemical CO sensor 1 has a thin box shape or when the wiring board 120 is a flexible wiring board. .

  Further, with the configuration as in the second embodiment, the resistance to noise can be improved more stably than when the inside of the wiring board 120 is routed by a thin circuit pattern and grounded via a chip capacitor.

  In the above-described embodiment, the CO alarm device that measures the CO concentration and performs the alarm operation using the electrochemical CO sensor 1 has been described as an example. However, the present invention is not limited to CO, and may be oxygen, carbon dioxide, or the like. Needless to say, the present invention is widely applicable when measuring the gas concentration of the target gas with an electrochemical gas sensor.

It is a perspective view showing one embodiment of a CO alarm with a built-in electrochemical CO sensor to which the present invention is applied. It is sectional drawing which shows the structure of the electrochemical CO sensor incorporated in the CO alarm device with an electrochemical CO sensor of FIG. FIG. 2 is a circuit diagram of an electrical configuration built in the electrochemical CO sensor built-in CO alarm device of FIG. 1. It is a figure for demonstrating the relationship between the electrochemical CO sensor of Example 2, and a wiring board. It is a partial cross section schematic diagram for demonstrating the relationship between the metal can in FIG. 4, a GND solid pattern, and an insulating member. It is a side view of the direction X shown by the arrow in FIG. It is sectional drawing which shows the structure of a general electrochemical CO sensor.

Explanation of symbols

1 Electrochemical CO sensor (electrochemical gas sensor)
2 Metal can (container)
3 Proton Conductor Membrane 31 Detection Electrode 32 Counter Electrode 4 Upper Opening 5 Water 8 Metal Cap (Cap)
20 Signal processing circuit 100 CO alarm with built-in electrochemical CO sensor (Gas alarm with built-in electrochemical gas sensor)
110 Case 120 Wiring board 130 GND solid pattern (metal member)
140 Insulating member C Capacitor IC2 Second switch circuit (switch)

Claims (3)

Oxidation reaction of the target gas existing in the ambient atmosphere of the container generated at the detection electrode of the proton conductor film fixed to the upper opening of the container containing water inside, and the counter electrode of the proton conductor film An electrochemical formula that generates a current of a magnitude according to the concentration of the target gas in the ambient atmosphere of the container between the detection electrode and the counter electrode by a reduction reaction of the proton generated by the oxidation reaction that occurs. A gas sensor and a signal processing circuit connected to the detection electrode and the counter electrode for converting the current into a gas concentration signal having a voltage value corresponding to the concentration of the target gas in the ambient atmosphere of the container are incorporated in the case, and A gas alarm that outputs an alarm when the concentration of the target gas in the ambient atmosphere of the container indicated by the gas concentration signal reaches an alarm level;
The container is configured by a metal can that also serves as a metal shield member that covers the container, the counter electrode is electrically connected to the metal can, and the terminal on the counter electrode is configured by the metal can, The gas alarm with a built-in electrochemical gas sensor, wherein the metal can is connected to a ground potential portion of the signal processing circuit through a capacitor . A switch that can be switched from an open state to a closed state during measurement of the concentration of the target gas in the ambient atmosphere of the metal can is provided between the metal can and the signal processing circuit, and the switch and the metal The gas alarm with a built-in electrochemical gas sensor according to claim 1 , wherein a space between the can and the can is connected to a ground potential portion of the signal processing circuit via the capacitor. Oxidation reaction of the target gas existing in the ambient atmosphere of the container generated at the detection electrode of the proton conductor film fixed to the upper opening of the container containing water inside, and the counter electrode of the proton conductor film An electrochemical formula that generates a current of a magnitude according to the concentration of the target gas in the ambient atmosphere of the container between the detection electrode and the counter electrode by a reduction reaction of the proton generated by the oxidation reaction that occurs. A gas sensor and a signal processing circuit connected to the detection electrode and the counter electrode for converting the current into a gas concentration signal having a voltage value corresponding to the concentration of the target gas in the ambient atmosphere of the container are built in the case, A gas alarm that outputs an alarm when the concentration of the target gas in the ambient atmosphere of the container indicated by the gas concentration signal reaches an alarm level;
A metal shield member disposed between the case and the container to cover the container and to which the counter electrode is electrically connected;
A metal member that is interposed between the shield member and the case so as to face the metal shield member and is grounded;
An insulating member interposed so as to insulate between the metal shield member and the metal member;
A gas alarm with a built-in electrochemical gas sensor.

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