JP2018066634A - Sensor unit and notification system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor unit and a notification system which can suppress false detection of a detection target gas.SOLUTION: The sensor unit 210 (gas detector 200) includes: a sensor 100 containing an electrolytic solution, the sensor including an electrolytic solution container 2 in which a working electrode 11 and a reference electrode are arranged; a potentiostat circuit 3 for making the potential difference between the working electrode 11 and the reference electrode a constant potential to detect an electrochemical reaction of a detection target gas G; and a detection circuit 5 separately provided from the potentiostat circuit 3, the detection circuit detecting changes in the potential of the working electrode 11 caused for a reason other than the electrochemical reaction of the detection target gas G.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sensor unit and a notification system.

  Conventionally, sensor units are known (see, for example, Patent Document 1).

  Patent Document 1 discloses a constant potential electrolytic gas sensor (sensor unit) including an electrolyte cell, a working electrode, a counter electrode, and a reference electrode. This constant potential electrolytic gas sensor is provided with a potentiostat circuit connected to a working electrode, a counter electrode, and a reference electrode. The potentiostat circuit is configured to make the potential difference between the working electrode and the reference electrode constant. When the gas to be detected is introduced into the electrolyte cell and an electrochemical reaction occurs in the working electrode, the potential of the working electrode tends to change according to the gas to be detected. On the other hand, when a current flows between the working electrode and the counter electrode by the potentiostat circuit, the potential of the working electrode is kept substantially constant. Here, the magnitude of the current passed by the potentiostat circuit at this time is proportional to the concentration of the gas to be detected. Therefore, the constant potential electrolytic gas sensor is configured to detect the concentration of the gas to be detected based on the current value of the current passed by the potentiostat circuit.

Japanese Patent No. 4458795

  However, in the constant potential electrolytic gas sensor described in Patent Document 1, current may flow between the working electrode and the counter electrode due to factors other than the electrochemical reaction of the gas to be detected at the working electrode. For example, when electrical noise (external noise) enters the potentiostat circuit or sensor (working electrode), when the surface condition of the working electrode changes temporarily, or when the working electrode or counter electrode deteriorates over time For example, the potential of the working electrode changes. At this time, a temporary current is caused to flow by the potentiostat circuit so as to restore the change in potential of the working electrode. In this case, in the constant potential electrolytic gas sensor (sensor unit) of Patent Document 1, an output value indicating that the detected gas is detected is incorrect due to factors other than the electrochemical reaction of the detected gas at the working electrode. Output (incorrect detection of detected gas).

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a sensor unit and a notification system capable of suppressing erroneous detection of a gas to be detected. Is to provide.

  The inventor of the present application has intensively studied to solve the above-described problems. As a result, in the sensor unit, when a gas to be detected is detected, a current is passed by the sensor drive circuit, and the potential of the working electrode does not change. It was found that a transient change in the potential of the working electrode was observed for factors other than the electrochemical reaction of the gas. Based on this knowledge, the inventors have come up with the following invention. That is, the sensor unit according to the first aspect of the present invention accommodates an electrolytic solution and detects an electrochemical reaction between a sensor including an electrolytic solution housing portion in which a working electrode and a reference electrode are arranged, and a gas to be detected. Therefore, the sensor drive circuit that sets the potential difference between the working electrode and the reference electrode to a constant potential and the sensor drive circuit are provided separately, and the change in the potential of the working electrode caused by factors other than the electrochemical reaction of the gas to be detected And a detection circuit for detecting.

  As described above, the sensor unit is provided separately from the sensor drive circuit, and is provided with a detection circuit that detects a change in potential of the working electrode caused by factors other than the electrochemical reaction of the gas to be detected. It can be detected that the potential of the working electrode has changed due to factors other than the electrochemical reaction of the gas. This makes it possible to distinguish between the case where the gas to be detected is detected and the case where the potential of the working electrode changes due to a factor other than the electrochemical reaction of the gas to be detected. Can be suppressed.

  In the sensor unit according to the first aspect, the detection circuit is preferably configured to detect a change of the potential of the working electrode with respect to the reference potential. If comprised in this way, the change of a working electrode can be easily detected by comparing the electric potential of a working electrode, and a reference potential with a detection circuit.

  In this case, preferably, the sensor includes a reference electrode that is disposed in the electrolyte container and has a reference potential, and the detection circuit has one input end that is at the same potential as the working electrode and the other input end that is the reference potential. A voltage comparison circuit connected to the electrode and outputting a signal based on a potential difference between the working electrode and the reference electrode is included. If comprised in this way, the signal based on the electric potential difference of a working electrode and a reference electrode can be acquired as a change of the electric potential of the working electrode produced by factors other than the electrochemical reaction of to-be-detected gas. As a result, by providing the reference electrode and the voltage comparison circuit, a change in the potential of the working electrode can be easily detected.

  In the sensor unit including the reference electrode, the reference electrode is preferably connected to the other input terminal of the voltage comparison circuit without being connected to the sensor driving circuit. With this configuration, noise that has entered the sensor drive circuit can be prevented from being input to the voltage comparison circuit via the reference electrode, so that a change in the potential of the working electrode can be detected more accurately. Can do.

  In the sensor unit including the reference electrode, the working electrode is preferably connected to a sensor drive circuit, and the sensor drive circuit and the voltage comparison circuit are connected to a common ground potential unit. With this configuration, the potential of the working electrode and the potential of one input terminal of the voltage comparison circuit are set to the same potential without directly connecting the working electrode and the voltage comparison circuit via the common ground potential portion. Can do. Here, when the working electrode and the voltage comparison circuit are directly connected, a wiring for directly connecting the working electrode and the voltage comparison circuit is provided separately from the wiring for connecting the working electrode and the sensor drive circuit. There is a need. In this case, the configuration in the vicinity of the working electrode is complicated. In this regard, in the present invention, since the working electrode and the voltage comparison circuit can be connected to each other through a common ground potential portion without being directly connected, the configuration in the vicinity of the working electrode can be achieved. The potential of the working electrode can be compared with the reference potential while suppressing the complication.

  In the sensor unit including the voltage comparison circuit, the sensor drive circuit and the voltage comparison circuit are preferably disposed on the same substrate. If comprised in this way, unlike the case where a sensor drive circuit and a voltage comparison circuit are arrange | positioned on a separate board | substrate, it can suppress that a number of parts increases.

  A notification system according to a second aspect of the present invention includes a sensor unit including the reference electrode, a notification unit that performs notification based on detection of a gas to be detected, and a notification unit based on a current value flowing through the sensor drive circuit. Control means for controlling notification, the control means obtains a signal based on the potential difference between the working electrode and the reference electrode output from the voltage comparison circuit, and if there is no potential difference, the value of the current flowing in the sensor drive circuit On the basis of the control, the notification means detects the detection of the detected gas, and when there is a potential difference, the notification means performs the control not to notify the detection of the detection gas.

  With the notification system according to the second aspect of the present invention, it is possible to provide a notification system capable of suppressing erroneous detection of the gas to be detected by configuring as described above.

  According to the present invention, it is possible to suppress erroneous detection of the gas to be detected as described above.

It is the block diagram which showed the structure of the gas detector by 1st Embodiment of this invention. It is the side view which showed typically the external shape of the sensor unit by 1st Embodiment of this invention. It is the figure which showed typically the circuit structure of the sensor by 1st Embodiment of this invention. It is the figure which showed typically the inside of the sensor unit by 1st Embodiment of this invention. It is sectional drawing which showed the structure of the sensor by 1st Embodiment of this invention. It is the figure which showed the structure of the gas electrode of the sensor by 1st Embodiment of this invention, and a reference electrode. It is a figure for demonstrating the output value at the time of the detection of the to-be-detected gas of the sensor by 1st Embodiment of this invention, and the time of the detection of external noise. It is a flowchart which shows the control processing regarding the alerting | reporting of the detection of the to-be-detected gas of the gas detector by 1st Embodiment of this invention. It is a flowchart which shows the control processing regarding alerting | reporting of the replacement time of the gas detector by 1st Embodiment of this invention. It is the figure which showed the structure of the gas electrode of the sensor by 2nd Embodiment of this invention, and a reference electrode. It is sectional drawing which showed the structure of the sensor by 3rd Embodiment of this invention. It is sectional drawing which showed the structure of the sensor by the 1st modification of the 1st-3rd embodiment of this invention, and a 2nd modification.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

[First Embodiment]
With reference to FIGS. 1-6, the structure of the sensor 100 (sensor unit 210) by 1st Embodiment of this invention is demonstrated.

  The sensor 100 according to the first embodiment constitutes a part of the gas detector 200 that detects the gas G to be detected and notifies the presence of the gas G to be detected. For example, the gas detector 200 is configured to notify that the detected gas G is detected when the detected concentration of the detected gas G is higher than a predetermined concentration.

(Configuration of gas detector and notification system)
As shown in FIG. 1, the gas detector 200 includes a sensor unit 210 including the sensor 100 and a main body unit 220. The main unit 220 includes a notification control unit 221, a notification unit 222, a power supply unit 223, a storage unit 224, a connection unit 225, and a gas conduction path 226. That is, the gas detector 200 includes a sensor 100 that detects the gas to be detected G, a notification unit 222 that notifies the detection of the detection gas G, and a notification control unit 221 that controls the notification unit 222. It is configured.

  Specifically, the notification control unit 221 includes, for example, a CPU (Central Processing Unit). The notification control unit 221 is configured to acquire an output value V1 indicating detection (detected concentration) of the gas G to be detected from the sensor 100 of the sensor unit 210 via the connection unit 225. And the alerting | reporting control part 221 is comprised so that it may alert | report that the to-be-detected gas G was detected by the alerting | reporting part 222 based on the acquired output value V1.

  Specifically, the notification unit 222 includes a display unit 222a and an audio output unit 222b. For example, when the acquired output value V1 exceeds a predetermined threshold value Vt1, the notification control unit 221 displays a display indicating detection of the detected gas G from the display unit 222a, or detects from the audio output unit 222b. It is configured to perform at least one of outputting a sound indicating the detection of the gas G.

  The power supply unit 223 includes, for example, a battery, and is configured to supply power to each unit of the main unit 220 and to supply power to the sensor unit 210 via the connection unit 225. The storage unit 224 is configured to store, for example, an output value V1 from the sensor 100 and potential difference information of the working electrode 11 described later in association with time information. The gas conduction path 226 is configured to introduce the gas to be detected G from the outside of the gas detector 200 and to conduct (wind) the gas to be detected G to the sensor 100.

(Configuration of sensor unit)
The sensor unit 210 is configured to be detachable from the gas detector 200. Thereby, the sensor unit 210 is configured to be replaceable when the type of the gas G to be detected is changed or when the sensor 100 is replaced (during the end of its life). Specifically, the sensor unit 210 is configured to be accommodated in the main body unit 220. Then, in a state where the sensor unit 210 is accommodated in the main unit 220, the sensor side connection part 212 of the sensor unit 210 is connected to the connection part 225 of the main unit 220, and the gas inlet 24a of the sensor unit 210 is It is configured to be connected to the gas conduction path 226.

  The sensor unit 210 is configured to be able to detect, as the gas to be detected G, for example, a semiconductor special material gas such as diborane, silane, phosphine, germane, and arsine, and a gas such as ozone or carbon monoxide. Yes.

  As shown in FIG. 2, the sensor unit 210 includes the sensor 100 and a housing portion 211 configured to cover the sensor 100 from the outside. Further, the sensor unit 210 includes a potentiostat circuit 3 and a detection circuit 5 as shown in FIG. The housing | casing part 211 is comprised with the metal, for example. The casing 211 is provided with a casing opening 211a and a seal member 211b. The housing opening 211a opens so as to expose the gas permeable membrane 22 of the sensor 100 when viewed from the arrow Y1 direction side. The potentiostat circuit 3 is an example of the “sensor drive circuit” in the claims.

  The housing opening 211 a is arranged at a position corresponding to the gas conduction path 226 of the main unit 220 when attached to the main unit 220. Thereby, when the sensor unit 210 is attached to the main unit 220, the gas G to be detected outside the gas detector 200 is introduced to the sensor 100 (the gas permeable membrane 22). Further, the seal member 211b is disposed along the edge of the housing opening 211a, and is sealed in a state where air can be guided between the gas conduction path 226 of the main unit 220 and the sensor 100. It is configured. In addition, the sensor side connection unit 212 is provided in the housing unit 211.

(Sensor configuration)
As shown in FIG. 3, the sensor 100 includes a gas electrode 1 and an electrolyte solution storage unit 2. That is, the sensor 100 is configured as an electrochemical sensor that detects an electrochemical reaction of the gas G to be detected using the gas electrode 1 and the electrolytic solution 21 accommodated in the electrolytic solution storage unit 2. The sensor 100 is configured as a constant potential electrolytic sensor using the potentiostat circuit 3 and the detection resistor 4.

  The sensor unit 210 includes a first substrate 120 as shown in FIG. The sensor 100 includes an electrolytic cell 23 and a second substrate 110a. The gas electrode 1, the electrolytic solution storage unit 2, and the detection resistor 4 are disposed on the sensor 100, and the potentiostat circuit 3 is disposed on the first substrate 120. In the present specification, “the circuit is arranged on the substrate” means that all of the elements (electronic components) and the conductive pattern constituting the circuit need not be arranged on the substrate, and the elements constituting the circuit. It is described as meaning that at least a part of is mounted on the substrate.

  As shown in FIG. 3, the gas electrode 1 includes a working electrode 11 for detecting an electrochemical reaction of the gas G to be detected, a counter electrode 12 for the working electrode 11, and a reference electrode for controlling the potential of the working electrode 11. 13 and so on.

  The working electrode 11 has a function as a reaction electrode for electrochemically reacting the gas to be detected G (target substance), and also has a function as a detection electrode for detecting the gas to be detected G (target substance). The counter electrode 12 has a function of flowing a current when the potential of the working electrode 11 is controlled. The working electrode 11, the counter electrode 12, and the reference electrode 13 are each connected to the potentiostat circuit 3.

  The working electrode 11, the counter electrode 12, and the reference electrode 13 are provided in the electrolytic solution storage unit 2 and are in contact with the electrolytic solution 21 stored in the electrolytic solution storage unit 2. In addition, the working electrode 11, the counter electrode 12, and the reference electrode 13 are arranged away from each other without contacting each other. The working electrode 11, the counter electrode 12, and the reference electrode 13 are formed by applying a paste-like electrode material to the gas permeable film 22 and baking it. For example, the working electrode 11, the counter electrode 12, and the reference electrode 13 include carbon black as an electrode material.

  The gas permeable membrane 22 is configured not to transmit the electrolytic solution 21 and configured to transmit the gas G to be detected. For example, the gas permeable membrane 22 is formed of porous PTFE (polytetrafluoroethylene) having water repellency.

  Further, as shown in FIG. 5, the gas permeable membrane 22 includes a first permeable membrane 22a configured as one surface (a surface on the arrow Y1 direction side) of the electrolytic solution housing portion 2, and the first permeable membrane 22a and the electrolyzed membrane. And a second permeable membrane 22b configured as the other surface (surface on the arrow Y2 direction side) of the electrolyte solution storage part 2 that faces the liquid 21 therebetween. The working electrode 11 is arranged on the electrolyte solution 21 side (arrow Y2 direction side) of the first permeable membrane 22a, and the counter electrode 12 and the reference electrode 13 are on the electrolyte solution 21 side of the second permeable membrane 22b (see FIG. (Arrow Y1 direction side).

  Specifically, as shown in FIG. 6, the surface area A1 of the working electrode 11 that contacts the electrolytic solution 21 is larger than the surface area A2 of the counter electrode 12 that contacts the electrolytic solution 21, and the electrolytic solution 21 of the reference electrode 13 It is larger than the contact surface area A3. For example, the first permeable membrane 22a and the second permeable membrane 22b have substantially the same area on the XY plane. The working electrode 11 is provided so as to cover substantially the entire surface of the first permeable membrane 22a on the electrolyte solution 21 side (arrow Y2 direction side), while the counter electrode 12 and the reference electrode 13 are provided on the second permeable membrane 22b. It is provided so as to cover a part.

  Moreover, the electrolyte solution 21 is comprised by acidic aqueous solution or neutral salt aqueous solution etc., for example. The acidic aqueous solution contains, for example, sulfuric acid and phosphoric acid. The neutral salt aqueous solution contains lithium bromide, calcium chloride, and the like.

  As shown in FIG. 5, the sensor 100 includes an electrolytic bath 23 that constitutes the electrolytic solution storage unit 2, a first lid member 24 that fixes the first permeable membrane 22 a, and a second one that fixes the second permeable membrane 22 b. 2 between the first lid member 25, the first O-ring 26 a disposed so as to be sandwiched between the first permeable membrane 22 a and the first lid member 24, and between the second permeable membrane 22 b and the second lid member 25. And a second O-ring 26b arranged to be sandwiched.

  The first lid member 24 is provided with a gas inlet 24a. Thus, the first permeable membrane 22a comes into contact with the detected gas G guided through the housing opening 211a and the gas conduction path 226 via the gas introduction port 24a. The first permeable membrane 22a transmits the gas G to be detected, and the sensor 100 is configured such that the gas G to be detected undergoes an electrochemical reaction (oxidation-reduction reaction) at the working electrode 11.

  The second lid member 25 is provided with an opening 25a. Thereby, the 2nd permeable film 22b is comprised so that the air (atmosphere gas) inside the housing | casing part 211 may permeate | transmit through the opening part 25a.

  As shown in FIG. 3, the potentiostat circuit 3 controls the potential difference between the working electrode 11 and the reference electrode 13 to be a constant potential (constant potential difference) in order to detect the electrochemical reaction of the gas G to be detected. Configured to do. For example, when the gas G to be detected undergoes an electrochemical reaction at the working electrode 11, a current is passed through the working electrode 11 and the counter electrode 12 to make the potential difference between the working electrode 11 and the reference electrode 13 constant. . At this time, a current flows through the detection resistor 4.

  Moreover, the detection resistor 4 is arrange | positioned at the 2nd board | substrate 110a (refer FIG. 3). Further, the second substrate 110 a is disposed closer to the electrolytic cell 23 than the first substrate 120. The first substrate 120 and the second substrate 110a are connected via a wiring (not shown).

  Then, the sensor unit 210 is configured to acquire a current value of a current flowing between the working electrode 11 and the counter electrode 12 by detecting a voltage drop value of the detection resistor 4. Specifically, the sensor unit 210 includes an AD conversion (analog / digital conversion) circuit 6. The AD conversion circuit 6 is arranged on the first substrate 120, and the notification value of the main body unit 220 is controlled by setting the current value (voltage drop value of the detection resistor 4) flowing through the potentiostat circuit 3 as the digital output value V1. It is comprised so that it may transmit to the part 221.

  Specifically, the potentiostat circuit 3 is provided with a first amplifier 31 (an operational amplifier) and a second amplifier 32. For example, the working electrode 11 is connected to the non-inverting input terminal 31 a of the first amplifier 31 and is connected to the detection resistor 4. The inverting input terminal 31 b of the first amplifier 31 is connected (grounded) to the ground 120 a of the first substrate 120. The output terminal 31 c of the first amplifier 31 is connected to the detection resistor 4 and to the AD conversion circuit 6.

  The reference electrode 13 is connected to the non-inverting input terminal 32 a of the second amplifier 32. The inverting input terminal 32 b of the second amplifier 32 is connected (grounded) to the ground 120 a of the first substrate 120. The output end 32 c is connected to the counter electrode 12. Thus, the potentiostat circuit 3 is configured such that the inverting input terminal 31b of the first amplifier 31 and the inverting input terminal 32b of the second amplifier 32 have the same potential via the ground 120a. As a result, when an electrochemical reaction occurs in the working electrode 11, a current flows from the potentiostat circuit 3 to the working electrode 11 and the counter electrode 12 in order to maintain the same potential state. At this time, a current flows through the detection resistor 4. The AD conversion circuit 6 is configured to transmit the current value flowing through the detection resistor 4 to the notification control unit 221 as the output value V1.

(Configuration for detecting changes in potential of working electrode)
Here, in 1st Embodiment, the gas detector 200 is comprised so that the change of the electric potential produced by factors other than the electrochemical reaction of the to-be-detected gas G of the sensor 100 may be detected. Specifically, in the first embodiment, the sensor unit 210 is configured to detect a change in the potential of the working electrode 11 caused by factors other than the electrochemical reaction of the gas G to be detected.

  Here, the change in the potential of the working electrode 11 is caused by the influence of noise (electrical noise), the influence of the surface state of the working electrode 11 (or the reference electrode 13), or the deterioration of the working electrode 11 with time. Note that a change in the potential of the working electrode 11 may occur due to cases other than the above-described case of noise or the like. In the first embodiment, the sensor unit 210 is configured to detect a change in the potential of the working electrode 11 caused by at least one of noise as a factor other than the electrochemical reaction of the gas G to be detected and deterioration with time of the working electrode 11. Has been. The electrochemical reaction is, for example, an oxidation-reduction reaction.

  For example, the noise of the wiring connected to the working electrode 11 and the ground 120a of the first substrate 120 or the working electrode 11 or the reference electrode 13 itself changes the potential of the working electrode 11 or the reference electrode 13. Immediately after the sensor unit 210 is manufactured (initial use), the wettability (water repellency) of the working electrode 11 (or the reference electrode 13) with respect to the electrolytic solution 21 tends to fluctuate temporarily. In this case, the immersion potential of the working electrode 11 (or the reference electrode 13) temporarily changes. Also, when a substance having a unique potential different from the electrode material of the working electrode 11 adheres to the working electrode 11, the immersion potential changes temporarily. In addition, the working electrode 11 is in contact with the gas G to be detected, and the gas G to be detected undergoes an electrochemical reaction at the working electrode 11, so that the catalytic function of the working electrode 11 deteriorates with time. In this case, the potential changes due to a decrease in the catalytic function of the working electrode 11.

  Therefore, in the first embodiment, the sensor 100 includes the reference electrode 14. The reference electrode 14 is disposed in the electrolytic solution storage unit 2 and has a function different from that of the working electrode 11, the counter electrode 12, and the reference electrode 13. Specifically, the reference electrode 14 has a function for detecting a change in the potential of the working electrode 11 caused by factors other than the electrochemical reaction of the gas G to be detected. Specifically, the reference electrode 14 has a reference potential as a function for detecting a change in the potential of the working electrode 11.

  The reference electrode 14 is arranged in the electrolytic solution container 2 so as to contact the electrolytic solution 21 without contacting the working electrode 11, the counter electrode 12, and the reference electrode 13. Specifically, as shown in FIGS. 5 and 6, the reference electrode 14 is provided on the second permeable membrane 22 b (the other side of the electrolyte solution storage unit 2) where the counter electrode 12 and the reference electrode 13 are provided. ing. That is, the reference electrode 14 is disposed on the same plane as the counter electrode 12 and the reference electrode 13, while being disposed at a position facing the working electrode 11 with the electrolytic solution 21 interposed therebetween.

  The reference electrode 14 includes at least one electrode material of carbon black, silver, platinum, gold, or palladium. In the first embodiment, the reference electrode 14 includes carbon black and includes the same material as the working electrode 11, the counter electrode 12, and the reference electrode 13. Specifically, the reference electrode 14 is formed by applying an electrode material to the second permeable film 22b and baking it. For example, as shown in FIG. 6A, the electrode material is applied to the second permeable film 22b and is fired so that the electrode material application region is divided into three in the direction along the Z axis (vertical direction). Thus, the counter electrode 12, the reference electrode 13, and the reference electrode 14 are formed.

  Specifically, the reference electrode 14 is configured so as not to contact the gas G to be detected by being provided on the second permeable film 22b. Further, the surface area A4 of the reference electrode 14 in contact with the electrolytic solution 21 is smaller than the surface area A1 of the working electrode 11 in contact with the electrolytic solution 21.

  Further, as shown in FIG. 3, the reference electrode 14 is not connected to the potentiostat circuit 3 to which the gas electrode 1 is connected. Thus, the reference electrode 14 has a reference potential that is a reference potential with respect to the potentiostat circuit 3 (working electrode 11).

  Here, in the first embodiment, the sensor unit 210 includes the detection circuit 5 provided separately from the potentiostat circuit 3. The detection circuit 5 is disposed on the first substrate 120 (see FIG. 4). That is, in the first embodiment, the detection circuit 5 is a circuit separate from the potentiostat circuit 3, but is disposed on the same substrate as the first substrate 120 on which the potentiostat circuit 3 is disposed. . The detection circuit 5 includes a voltage comparison circuit 51.

  In the present specification, “the circuit is provided separately” means that the circuit is not directly connected, for example, even though it is indirectly connected through the same ground. Good. In addition, separate circuits may be formed in one substrate and one electronic component (chip). That is, the voltage comparison circuit 51 (operational amplifier or comparator) of the detection circuit 5 may be provided in the same chip (electronic component) as the first amplifier 31 or the second amplifier 32 of the potentiostat circuit 3, for example. .

  In the voltage comparison circuit 51, the non-inverting input terminal 51 a is connected (grounded) to the ground 120 a of the first substrate 120, and the inverting input terminal 51 b is connected to the reference electrode 14. In other words, the non-inverting input end 51 a is connected to the working electrode 11 through the ground 120 a of the first substrate 120 and is configured to have the same potential as the working electrode 11. Thereby, the voltage comparison circuit 51 is configured to acquire a potential difference between the working electrode 11 and the reference electrode 14. That is, the potentiostat circuit 3 and the voltage comparison circuit 51 are connected to a common ground 120a. The non-inverting input terminal 51a is an example of “one input terminal” in the claims. The inverting input terminal 51b is an example of the “other input terminal” in the claims. The ground 120a is an example of the “ground potential portion” in the claims.

  The voltage comparison circuit 51 outputs a signal based on the potential difference between the working electrode 11 and the reference electrode 14 as a change in the potential of the working electrode 11 caused by a factor other than the electrochemical reaction of the gas G to be detected from the output terminal 51c. It is configured to output to the AD conversion circuit 6.

  The AD conversion circuit 6 is configured to output a signal (potential difference information) based on the potential difference between the working electrode 11 and the reference electrode 14 to the notification control unit 221 as a digital signal output value V2. The potential difference information is configured as information indicating the value (magnitude) of the potential difference, for example. In addition, by converting the output value V2 into a digital signal, it is possible to improve detection accuracy as compared with the case where the output value V2 is transmitted to the notification control unit 221 as an analog signal.

  Thereby, when the potential of the working electrode 11 (or the reference electrode 13) changes due to factors other than the electrochemical reaction of the gas to be detected G, the potential difference is transferred from the detection circuit 5 to the notification control unit 221 via the AD conversion circuit 6. Information is communicated. When the electrochemical reaction of the gas G to be detected occurs at the working electrode 11, the output value V1 is transmitted from the AD conversion circuit 6 to the notification control unit 221. On the other hand, in the electrochemical reaction, the working electrode 11 Since no potential difference occurs with respect to the reference electrode 14, the potential difference information (output value V 2) is not transmitted from the detection circuit 5 to the notification control unit 221.

  Here, in the first embodiment, the notification control unit 221 determines the current flowing through the potentiostat circuit 3 when the output value V2 does not exceed the predetermined threshold value Vt2 (when there is no potential difference) based on the potential difference information. Based on the value (output value V1), the notification unit 222 is configured to perform control for notifying the detection of the gas G to be detected. The notification control unit 221 also notifies the notification unit 222 when the output value V2 exceeds a predetermined threshold value Vt2 (when there is a potential difference) based on the potential difference information, regardless of the magnitude of the output value V1. Thus, control is performed so as not to notify the detection of the gas to be detected G. As a result, the notification control unit 221 causes the erroneous detected gas when the output value V1 of the potentiostat circuit 3 exceeds the predetermined threshold value Vt1 due to factors other than the electrochemical reaction of the detected gas G. The detection of G is not notified.

  Further, the notification control unit 221 indicates that the working electrode 11 is in a state of deterioration with time by the notification unit 222 when the value of the output value V2 continuously exceeds the predetermined life threshold value Vt3 for a predetermined period. It is configured to perform control to perform notification (notification indicating that it is time to replace the sensor unit 210). This makes it possible to directly detect the deterioration of the working electrode 11 with time, so that the sensor unit 210 should be replaced at an appropriate time for replacement as compared to the case where the sensor unit 210 is replaced periodically. Is possible.

  In addition, the notification control unit 221 is based on data (output log) in which the potential difference information of the working electrode 11 stored in the storage unit 224 is associated with time information in the vicinity of the place where the gas detector 200 is disposed. The notification unit 222 is configured to perform control to display a display for suggesting environmental improvement.

(Sensor operation)
Next, the operation of the sensor unit 210 according to the first embodiment will be described with reference to FIG. 1, FIG. 3, and FIG. As a specific example, the operation when the gas to be detected G is introduced into the sensor unit 210 as shown in FIG. In FIG. 7A, the potential of the working electrode 11 is not changed due to factors other than the electrochemical reaction of the gas G to be detected. In addition, as shown in FIG. 7B, the operation when the potential of the working electrode 11 is changed due to a factor (external noise) other than the electrochemical reaction of the gas G to be detected will be described.

<Detection of detected gas>
As shown in FIG. 1, the gas to be detected G is introduced into the sensor unit 210 from the outside of the gas detector 200 via the gas conduction path 226. And the to-be-detected gas G permeate | transmits the 1st permeation | transmission film | membrane 22a (refer FIG. 3), and to-be-detected gas G carries out an electrochemical reaction under the catalytic action of the working electrode 11. FIG.

  As a result, as shown in FIG. 3, the potentiostat circuit 3 causes a current to flow through the working electrode 11 and the counter electrode 12, thereby making the potential difference between the working electrode 11 and the reference electrode 13 constant. At this time, a current flows through the detection resistor 4. 7A, the AD converter circuit 6 transmits the voltage drop value (current value) of the detection resistor 4 to the notification control unit 221 as the digital signal output value V1. When the output value V1 exceeds the threshold value Vt1, a notification indicating that the gas to be detected G has been detected is issued from the notification unit 222. At this time, the potential difference between the working electrode 11 and the reference electrode 14 does not change. That is, at this time, the output value V2 is substantially 0 (threshold value Vt2 or less).

<External noise detection>
As shown in FIG. 7B, when external noise is applied to the working electrode 11, a potential difference between the working electrode 11 and the reference electrode 14 is generated. Then, potential difference information (output value V 2) is transmitted from the voltage comparison circuit 51 of the detection circuit 5 to the notification control unit 221 via the AD conversion circuit 6. At this time, in the potentiostat circuit 3, a current flows between the working electrode 11 and the counter electrode 12, and the output value V <b> 1 is transmitted from the AD conversion circuit 6 to the notification control unit 221. That is, when external noise is applied to the working electrode 11, the external noise is detected as the output value V2.

  As described above, in the sensor unit 210 according to the first embodiment, when the gas to be detected G is detected (FIG. 7A), factors other than the electrochemical reaction of the gas to be detected G (for example, external noise) Thus, it is possible to distinguish from the case where the potential of the working electrode 11 changes (FIG. 7B).

(Control processing related to notification of detection of gas to be detected by gas detector)
Next, with reference to FIG. 8, the control process regarding the notification of the detection of the gas G to be detected by the gas detector 200 (notification system) according to the first embodiment will be described. Control processing of the gas detector 200 is executed by the notification control unit 221.

  In step S <b> 1, it is determined whether there is a potential difference between the working electrode 11 and the reference electrode 14. Specifically, it is determined whether or not the output value V2 acquired from the sensor unit 210 exceeds the threshold value Vt2. If the output value V2 exceeds the threshold value Vt2, assuming that there is a potential difference between the working electrode 11 and the reference electrode 14, step S1 is repeated, and if the output value V2 becomes equal to or less than the threshold value Vt2, the working electrode 11 Assuming that there is no potential difference between the reference electrode 14 and the reference electrode 14, the process proceeds to step S2. That is, when there is a potential difference between the working electrode 11 and the reference electrode 14, the control process related to the notification of the detected gas G after step S2 is not performed.

  In step S2, it is determined whether or not the gas to be detected G has been detected. Specifically, it is determined whether or not the output value V1 acquired from the sensor unit 210 exceeds the threshold value Vt1. If the output value V1 exceeds the threshold value Vt1, it is determined that the detected gas G has been detected, and the process proceeds to step S3. If the output value V1 is equal to or lower than the threshold value Vt1, the detected gas G is not detected. Return to step S1.

  In step S <b> 3, the notification unit 222 notifies that the detected gas G has been detected. Then, the control process regarding the notification of the detection of the gas G to be detected by the gas detector 200 according to the first embodiment is ended.

(Control processing related to notification of gas detector replacement time)
Next, with reference to FIG. 9, the control process regarding the notification of the replacement time of the sensor unit 210 of the gas detector 200 according to the first embodiment will be described. Control processing of the gas detector 200 is executed by the notification control unit 221.

  In step S <b> 11, it is determined whether there is a potential difference between the working electrode 11 and the reference electrode 14. Specifically, it is determined whether or not the output value V2 acquired from the sensor unit 210 exceeds the threshold value Vt3. If the output value V2 exceeds the threshold value Vt3, it is determined that there is a potential difference between the working electrode 11 and the reference electrode 14, and the process proceeds to step S12. If the output value V2 is less than the threshold value Vt3, the working electrode 11 and the reference electrode Step S11 is repeated assuming that there is no potential difference with the electrode 14.

  In step S12, it is determined whether a potential difference has been detected continuously for a predetermined period. Specifically, it is determined whether or not the period in which the output value V2 acquired from the sensor unit 210 exceeds the threshold value Vt3 exceeds a predetermined period T1. When the period in which the output value V2 exceeds the threshold value Vt3 does not exceed the predetermined period T1, the process returns to step S11, and the period in which the output value V2 exceeds the threshold value Vt3 is the predetermined period T1. If exceeded, the process proceeds to step S13.

  In step S13, the notification unit 222 notifies that it is time to replace the sensor unit 210. Then, the control process regarding the notification of the replacement time of the gas detector 200 according to the first embodiment is ended.

[Effect of the first embodiment]
In the first embodiment, the following effects can be obtained.

  In the first embodiment, as described above, the sensor unit 210 is provided separately from the potentiostat circuit 3, and changes in the potential of the working electrode 11 caused by factors other than the electrochemical reaction of the gas to be detected G are detected. By providing the detection circuit 5 to detect, it is possible to detect that the potential of the working electrode 11 has changed due to factors other than the electrochemical reaction of the gas G to be detected. This makes it possible to distinguish between the case where the gas to be detected G is detected and the case where the potential of the working electrode 11 changes due to a factor other than the electrochemical reaction of the gas to be detected G. It can suppress that it is detected.

  In the first embodiment, as described above, the detection circuit 5 is configured to detect a change in the potential of the working electrode 11 with respect to the reference potential. Thereby, the change of the working electrode 11 can be easily detected by comparing the potential of the working electrode 11 with the reference potential by the detection circuit 5.

  Further, in the first embodiment, as described above, the sensor 100 is provided with the reference electrode 14 that is disposed in the electrolyte container 2 and has a reference potential. Further, the detection circuit 5 is configured such that the non-inverting input end 51 a is set to the same potential as the working electrode 11 and the inverting input end 51 b is connected to the reference electrode 14. The detection circuit 5 is provided with a voltage comparison circuit 51 that outputs a signal based on the potential difference between the working electrode 11 and the reference electrode 14. As a result, a signal based on the potential difference between the working electrode 11 and the reference electrode 14 can be acquired as a change in the potential of the working electrode 11 caused by factors other than the electrochemical reaction of the gas G to be detected. As a result, by providing the reference electrode 14 and the voltage comparison circuit 51, it is possible to easily detect a change in the potential of the working electrode 11.

  In the first embodiment, as described above, the reference electrode 14 is connected to the inverting input terminal 51 b of the voltage comparison circuit 51 without being connected to the potentiostat circuit 3. As a result, noise (external noise) that has entered the potentiostat circuit 3 can be suppressed from being input to the voltage comparison circuit 51 via the reference electrode 14, so that the potential of the working electrode 11 can be more accurately detected. Changes can be detected.

  In the first embodiment, as described above, the working electrode 11 is connected to the potentiostat circuit 3, and the potentiostat circuit 3 and the voltage comparison circuit 51 are connected to the common ground 120a. Thus, the potential of the working electrode 11 and the potential of the non-inverting input terminal 51a of the voltage comparison circuit 51 are set to the same potential without directly connecting the working electrode 11 and the voltage comparison circuit 51 via the common ground 120a. be able to. Here, when the working electrode 11 and the voltage comparison circuit 51 are directly connected, the working electrode 11 and the voltage comparison circuit 51 are directly connected separately from the wiring connecting the working electrode 11 and the potentiostat circuit 3. It is necessary to provide wiring for connection. In this case, the configuration in the vicinity of the working electrode 11 is complicated. With respect to this point, in the first embodiment, the working electrode 11 and the voltage comparison circuit 51 are not directly connected but connected via a common ground potential portion, whereby the potential of the working electrode 11 and the non-inverting input terminal 51a are connected. Therefore, the potential of the working electrode 11 and the reference potential can be compared while suppressing the complication of the configuration in the vicinity of the working electrode 11.

  In the first embodiment, as described above, the potentiostat circuit 3 and the voltage comparison circuit 51 are arranged on the same first substrate 120. Thereby, unlike the case where the potentiostat circuit 3 and the voltage comparison circuit 51 are arranged on separate substrates, it is possible to suppress an increase in the number of parts.

[Second Embodiment]
Next, the configuration of the sensor unit 300 of the second embodiment will be described with reference to FIG. Unlike the sensor unit 210 according to the first embodiment in which the reference electrode 14 is provided on the second permeable membrane 22b, the sensor unit 300 according to the second embodiment has the reference electrode 314 disposed on the first permeable membrane 22a. In addition, about the structure same as the said 1st Embodiment, the same code | symbol is attached | subjected and shown in the figure, and the description is abbreviate | omitted.

(Configuration of sensor unit according to the second embodiment)
As shown in FIG. 10, the sensor unit 300 according to the second embodiment of the present invention includes a working electrode 311, a counter electrode 312, a reference electrode 313, and a reference electrode 314. The working electrode 311 is disposed on the first permeable membrane 22a (see FIG. 10B), and the counter electrode 312 and the reference electrode 313 are disposed on the second permeable membrane 22b (see FIG. 10A). ing. Here, in 2nd Embodiment, the reference electrode 314 is arrange | positioned at the 1st permeable film 22a in which the working electrode 311 is provided.

  Specifically, as shown in FIG. 10B, the working electrode 311 and the reference electrode 314 are disposed on the first permeable membrane 22a without being in contact with each other. Further, the area A11 of the working electrode 311 and the area A14 of the reference electrode 314 viewed from the arrow Y1 direction side are substantially equal in size, and the area A12 of the counter electrode 312 and the reference electrode 313 viewed from the arrow Y2 direction side. The area A13 has substantially the same size. For example, the area A14 of the reference electrode 314 is equal to any of the areas A11 to A13. Other configurations and operations of the second embodiment are the same as those of the first embodiment.

[Effects of Second Embodiment]
In the second embodiment, the following effects can be obtained.

  In the second embodiment, as described above, the working electrode 311 is disposed on the first permeable membrane 22a, and the counter electrode 312 and the reference electrode 313 are disposed on the second permeable membrane 22b. Then, the reference electrode 314 is disposed on the first permeable membrane 22a. Accordingly, since the reference electrode 314 can be formed on the first permeable film 22a when the working electrode 311 is formed on the first permeable film 22a, the manufacturing process of the sensor unit 300 is prevented from being complicated. can do. The remaining effects of the second embodiment are similar to those of the aforementioned first embodiment.

[Third embodiment]
Next, the configuration of the sensor unit 400 of the second embodiment will be described with reference to FIG. Unlike the sensor unit 210 according to the first embodiment in which the first permeable membrane 22a and the second permeable membrane 22b are provided, the sensor unit 400 according to the third embodiment is provided with one gas permeable membrane 422. In addition, about the same structure as the said 1st Embodiment or 2nd Embodiment, the same code | symbol is attached | subjected and shown in the figure, and the description is abbreviate | omitted.

(Configuration of sensor unit according to the third embodiment)
The sensor unit 400 according to the third embodiment of the present invention includes a working electrode 411, a counter electrode 412, a reference electrode 413, and a reference electrode 414, as shown in FIG. The sensor unit 400 includes an electrolytic cell 423 that stores the electrolytic solution 21, and a lid member 424 that has a gas introduction port 424 a and is disposed on the arrow Y <b> 1 direction side of the electrolytic cell 423. A gas permeable membrane 422 is disposed between the electrolytic cell 423 and the lid member 424 with a packing 426 interposed therebetween.

  Here, in the third embodiment, the working electrode 411, the counter electrode 412, the reference electrode 413, and the reference electrode 414 are disposed on the same gas permeable membrane 422. Further, the counter electrode 412, the working electrode 411, the reference electrode 413, and the reference electrode 414 are arranged linearly in this order in a direction parallel to the Z axis. The reference electrode 414 is disposed on the gas permeable membrane 422 in the direction of arrow Z2 (lower side).

  In the third embodiment, the reference electrode 414 is made of the same shape and material as the reference electrode 413. The reference electrode 414 and the reference electrode 413 include silver, platinum, gold, or palladium as an electrode material. For example, both the reference electrode 414 and the reference electrode 413 are configured as silver wires. In addition, the other structure and operation | movement of 3rd Embodiment are the same as that of the said 1st Embodiment.

[Effect of the third embodiment]
In the third embodiment, the following effects can be obtained.

  In the third embodiment, as described above, the working electrode 411, the counter electrode 412, the reference electrode 413, and the reference electrode 414 are disposed on the same gas permeable membrane 422. The reference electrode 414 is made of the same material as the reference electrode 413. As a result, the reference electrode 414 can be configured in the same manner as the reference electrode 413 configured to be relatively insensitive to the detected gas G, and therefore, the detected gas G is passed through the gas permeable film 422. Even when the vehicle enters the vicinity, the influence of the electrochemical reaction caused by the gas G to be detected can be reduced. As a result, the potential change of the working electrode 411 can be detected using the reference electrode 414 with higher accuracy. The remaining effects of the third embodiment are similar to those of the aforementioned first embodiment.

[Modification]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims for patent, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first to third embodiments, the example in which the potentiostat circuit and the detection circuit are arranged on the same substrate is shown, but the present invention is not limited to this. That is, the potentiostat circuit and the detection circuit may be arranged on separate substrates.

  In the first to third embodiments, the voltage comparison circuit is provided in the detection circuit. However, the present invention is not limited to this. That is, the reference potential of the reference electrode and the potential of the working electrode may be individually transmitted to the notification control unit without providing the voltage comparison circuit in the detection circuit.

  Moreover, in the said 1st-3rd embodiment, although the notification control part and the notification part were provided in the main body unit, the present invention is not limited to this. That is, a notification control unit and a notification unit may be provided in the sensor unit.

  In the first to third embodiments, the example in which the working electrode, the counter electrode, the reference electrode, and the reference electrode are provided one by one is shown, but the present invention is not limited to this. For example, when two working electrodes are provided, two reference electrodes may be provided corresponding to each of the two working electrodes.

  Moreover, although the example which arrange | positions a reference | standard electrode in a gas permeable film was shown in the said 1st-3rd embodiment, this invention is not limited to this. For example, the reference electrode 514 may be disposed in the electrolytic cell 423 as in the sensor unit 500 of the first modified example shown in FIG.

  In the first to third embodiments, the detection circuit is configured to output the output value V2 indicating the potential difference between the working electrode and the reference electrode. However, the present invention is not limited to this. . For example, the detection circuit may be configured to output a high or low binary signal indicating whether or not there is a potential difference between the working electrode and the reference electrode.

  In the first to third embodiments, the example in which the reference electrode is configured to include the same material as that of the reference electrode has been described. However, the present invention is not limited to this. That is, the reference electrode may be composed only of a material different from the reference electrode.

  In the first to third embodiments, the example in which the electrode material of the reference electrode includes at least one of carbon black, silver, platinum, gold, or palladium is shown. The invention is not limited to this. That is, as long as it can be used as an electrode material, an electrode material other than carbon black, silver, platinum, gold, and palladium may be included in the electrode material of the reference electrode.

  In the first to third embodiments, the non-inverting input terminal of the voltage comparison circuit is configured to be connected to the working electrode via the ground of the first substrate. Not limited to. That is, the non-inverting input terminal of the voltage comparison circuit may be directly connected to the working electrode without passing through the ground of the first substrate.

  In the third embodiment, the reference electrode is disposed on the lower side (arrow Z2 direction side) of the gas permeable membrane. However, the present invention is not limited to this. For example, as in the sensor unit 600 of the second modification shown in FIG. 12B, the reference electrode 614 may be disposed above the counter electrode 412 of the gas permeable membrane 422 (arrow Z1 direction side).

  Moreover, in the said 1st-3rd embodiment, although the example (refer FIG. 6 and FIG. 10 etc.) of the area of a working electrode, a counter electrode, a reference electrode, and a standard electrode was shown, this invention is not limited to this. . For example, although the example in which the area A2 of the counter electrode 12 of the sensor 100 of the sensor unit 210 according to the first embodiment and the area A4 of the reference electrode 14 are configured to be approximately equal to each other is illustrated, the area of the counter electrode 12 and the reference electrode 14 You may comprise an area in a different magnitude | size. In addition, the area A11 of the working electrode 311, the area A12 of the counter electrode 312, the area A13 of the reference electrode 313, and the area A14 of the reference electrode 314 of the sensor unit 300 according to the second embodiment are configured to be substantially equal to each other. However, the areas of the working electrode 311, the counter electrode 312, the reference electrode 313, and the reference electrode 314 may be different from each other.

  In the first to third embodiments, examples of the control process (see FIG. 8) regarding the notification of the detection of the gas to be detected and the control process (see FIG. 9) regarding the notification of the replacement time have been shown. It is not limited to this. For example, the order of step S1 and step S2 may be switched in the control process related to notification of detection of the gas to be detected, or the order of step S11 and step S12 may be switched in the control process related to notification of the replacement time. Good. Further, in the control process related to the notification of the replacement time, it may be determined whether a predetermined time has elapsed from the use start time of the sensor, and the replacement time may be determined in consideration of the time from the start of use. That is, the sensor may be configured to start step S11 when a predetermined time has elapsed from the start of use, or if “Yes” in step S12, the sensor is used before step S13. A step of determining whether or not a predetermined time has elapsed since the start may be further provided.

  In the first to third embodiments, the sensor is configured to notify that the detected gas is detected when the detected concentration of the detected gas is higher than a predetermined concentration. The present invention is not limited to this. That is, the sensor may be configured to notify that the detected concentration of the detected gas is low when the detected concentration of the detected gas is lower than a predetermined concentration. For example, when the sensor is configured to detect oxygen as the gas to be detected, the sensor is configured to notify that the detected oxygen concentration is low when the detected oxygen concentration is lower than a predetermined concentration. To do.

  In the first to third embodiments, the gas detector includes a sensor that detects the gas to be detected, a notification unit that notifies detection of the gas to be detected, and a notification control unit that controls the notification unit. Although the example which comprises as an alerting | reporting system was shown, this invention is not limited to this. For example, the gas detector may be provided with only a sensor, and the notification unit and the notification control unit may be provided at positions separated from the sensor. In this case, for example, the notification unit and the notification control unit are preferably configured as part of a centralized monitoring system that monitors a plurality of sensors. In this case, the plurality of sensors and the centralized monitoring system are preferably configured to be able to perform wireless or wired communication with each other. In addition, a sensor and a notification unit may be provided in the gas detector, and only a different notification unit may be provided at another position. In this case, when detected gas is detected, you may comprise so that control which alert | reports from both the alerting | reporting part of a gas detector and the alerting | reporting part provided in another position may be performed. In addition, the notification system of the present invention may be configured as a notification system including a plurality of gas detectors.

1 Gas electrode (working electrode, counter electrode, reference electrode)
2 Electrolyte container 3 Potentiostat circuit (sensor drive circuit)
5 detection circuit 11, 311, 411 working electrode 13, 313, 413 reference electrode 14, 314, 414, 514, 614 reference electrode 21 electrolyte 51 voltage comparison circuit 51a non-inverting input terminal (one input terminal)
51b Inversion input terminal (the other input terminal)
100 Sensor 120a Ground (ground potential part)
210, 300, 400, 500, 600 Sensor unit 200 Gas detector (notification system)

Claims (7)

A sensor that contains an electrolyte solution and includes an electrolyte solution storage portion in which a working electrode and a reference electrode are disposed,
In order to detect the electrochemical reaction of the gas to be detected, a sensor drive circuit for setting a potential difference between the working electrode and the reference electrode to a constant potential;
A sensor unit, provided separately from the sensor drive circuit, and comprising a detection circuit for detecting a change in potential of the working electrode caused by a factor other than an electrochemical reaction of the gas to be detected.   The sensor unit according to claim 1, wherein the detection circuit is configured to detect a change of a potential of the working electrode with respect to a reference potential. The sensor includes a reference electrode disposed in the electrolyte container and having the reference potential,
The detection circuit has one input terminal having the same potential as the working electrode and the other input terminal connected to the reference electrode, and outputs a signal based on a potential difference between the working electrode and the reference electrode. The sensor unit according to claim 2, comprising a voltage comparison circuit.   The sensor unit according to claim 3, wherein the reference electrode is connected to the other input terminal of the voltage comparison circuit without being connected to the sensor drive circuit. The working electrode is connected to the sensor drive circuit;
The sensor unit according to claim 3 or 4, wherein the sensor driving circuit and the voltage comparison circuit are connected to a common ground potential section.   The sensor unit according to claim 3, wherein the sensor driving circuit and the voltage comparison circuit are arranged on the same substrate. The sensor unit according to any one of claims 3 to 6,
Notification means for performing notification based on detection of the detected gas;
Control means for controlling the notification of the notification means based on the value of the current flowing through the sensor drive circuit,
The control means obtains a signal based on a potential difference between the working electrode and the reference electrode output from the voltage comparison circuit, and when there is no potential difference, based on a current value flowing through the sensor drive circuit, A notification system configured to perform a control for notifying the detection of the detected gas by the notification means, and to perform a control not to notify the detection of the detected gas by the notification means when there is the potential difference. .

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