JP3686278B2 - Gas detection device and gas detection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention detects a gas such as carbon monoxide (CO) at the time of incomplete combustion or methane (CH ₄ ) at the time of city gas leakage with one gas sensor, and gas is detected when the gas concentration is equal to or higher than the alarm point concentration. Gas detection device and gas detection method for alarming that the concentration is abnormal with an alarm sound, an alarm lamp, an external output, etc., and in particular, gas detection equipped with a combined gas leak alarm that can easily perform CO inspection Relates to the device.
[0002]
[Prior art]
Conventionally, one gas sensor is periodically driven alternately in a low temperature region and a high temperature region to detect a composite gas such as carbon monoxide gas or methane gas. A conventional driving method of this type of gas sensor is shown in FIG.
[0003]
In FIG. 12, the timing chart of the temperature of the gas sensor in the conventional gas detection apparatus is shown. A semiconductor sensor for carbon monoxide is used as the gas sensor, and the temperature of the gas sensor is periodically and alternately changed between a low temperature range (100 ° C.) and a high temperature range (400 ° C.).
[0004]
In the low temperature range, the sensor temperature is maintained at 100 ° C. for 90 seconds, and the gas concentration of carbon monoxide is detected at the CO detection point (black circle in FIG. 12). In the high temperature range, the sensor temperature is maintained at 400 ° C. for only 60 seconds. The concentration of methane gas is detected. For this reason, it takes 150 seconds to detect CO once.
[0005]
In addition, when a construction company installs a gas detection device and performs a CO inspection, for example, CO is injected into the gas detection device, and an inspection cover is put in place to prevent CO leakage, and a CO inspection is performed. It was.
[0006]
[Problems to be solved by the invention]
However, in the conventional gas sensor, the period of the CO detection point is very long, for example, 150 seconds, and it takes a considerable time for the CO inspection work. In addition, when the gas detection device was installed, the inspection cover was covered and the CO inspection was carried out, so the inspection work was a difficult task.
[0007]
Further, the inspection point may be shifted or the carbon monoxide gas may be thin. In such a case, the CO inspection had to be performed again, and it took a considerable amount of time for the CO inspection work.
[0008]
Then, this invention makes it a subject to provide the gas detection apparatus and gas detection method which can perform CO inspection simply in a short time, without using the cover for inspection.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configuration. According to the first aspect of the present invention, the temperature of the gas sensor is periodically and alternately changed between a low temperature region and a high temperature region, the first gas concentration is detected in the low temperature region, the second gas concentration is detected in the high temperature region, and the first gas is detected. A first gas alarm indicating an abnormality in the first gas concentration is notified when the concentration exceeds the first gas alarm point, and the second gas concentration is detected when the second gas concentration exceeds the second gas alarm point. in the gas detection apparatus for notifying a second gas alarm indicating an abnormality, in the first gas alarm point is the first gas concentration during inspection mode of the first gas concentration in the first before the predetermined time has elapsed from power 1 A first alarm is notified when a second predetermined time has elapsed from when the second alarm point is reached, and the first gas concentration is higher than the first alarm point at the first gas alarm point. second to notify the alarm upon a more eye alarm point, the from the power-on 1 after a predetermined time has elapsed to notify the first alarm when the elapsed third predetermined time when the first gas concentration becomes the first stage or alarm point, the first gas concentration is the 2-stage An alarm delay control means for notifying the second alarm when a fourth predetermined time has elapsed from when the eye alarm point is reached is provided.
[0010]
According to the first aspect of the present invention, the alarm delay control means is configured such that when the first gas concentration becomes equal to or higher than the first-stage alarm point during the first gas concentration inspection mode before the first predetermined time has elapsed since the power is turned on. The first alarm is notified when the second predetermined time elapses, and the second alarm is notified when the first gas concentration is equal to or higher than the second-stage alarm point . In other words, a false alarm can be prevented by delaying the first alarm in the inspection mode, and the second alarm is immediately notified when the first gas concentration exceeds the second stage alarm point. The CO inspection can be performed easily in a short time without using. Further, after the first predetermined time has elapsed since the power was turned on, the first alarm is notified when the third predetermined time has elapsed since the first gas concentration has reached or exceeded the first stage alarm point, and the first gas concentration is 2 The second alarm is notified when the fourth predetermined time has elapsed since the stage alarm point was reached. That is, by setting the alarm delay time, it is possible to prevent the false alarm of the first gas concentration abnormality alarm.
[0017]
The invention of claim 2 periodically changes the temperature of the gas sensor between a low temperature region and a high temperature region, detects the first gas concentration in the low temperature region, detects the second gas concentration in the high temperature region, and detects the first gas. A first gas alarm indicating an abnormality in the first gas concentration is notified when the concentration exceeds the first gas alarm point, and the second gas concentration is detected when the second gas concentration exceeds the second gas alarm point. A gas detection method for notifying a second gas alarm indicating an abnormality, wherein the first gas concentration is in the first gas alarm point during the first gas concentration check mode before the first predetermined time has elapsed since power-on. When the second predetermined time elapses from when the first stage alarm point becomes higher than the first stage alarm point, the first gas concentration is greater than the first stage alarm point at the first gas alarm point. second to notify the alarm upon a two-stage or more alarm point, the from the power-on 1 after a predetermined time has elapsed to notify the first alarm when the elapsed third predetermined time when the first gas concentration becomes the first stage or alarm point, the first gas concentration is the 2-stage An alarm delay control step of notifying the second alarm when a fourth predetermined time elapses from when the eye alarm point is reached is included.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a gas detection device and a gas detection method of the present invention will be described in detail with reference to the drawings.
[0022]
FIG. 1 is a circuit configuration diagram of a gas detection device according to an embodiment of the present invention. FIG. 2 is a timing chart of the temperature of the gas sensor in the gas detection device of the embodiment. FIG. 3 is a flowchart for explaining a gas detection method realized by the gas detection apparatus of the embodiment. FIG. 4 is a flowchart for explaining CO alarm determination during the inspection mode in the gas detection method of FIG. FIG. 5 is a flowchart for explaining the processing when the state after the CO2 stage delay is YES in the gas detection method of FIG.
[0023]
FIG. 6 is a flowchart for explaining processing when the CO2 stage delay state in the gas detection method of FIG. 3 is YES. FIG. 7 is a flowchart for explaining the processing when the state after the delay of the first CO stage in the gas detection method of FIG. 3 is YES. FIG. 8 is a flowchart for explaining processing when the CO1 stage delay state in the gas detection method of FIG. 3 is YES. FIG. 9 is a flowchart for explaining processing when the CO1 stage delay state is NO in the gas detection method of FIG. FIG. 10 is a timing chart of the inspection mode less than 25 minutes after the power is turned on. FIG. 11 is a timing chart in the normal mode after 25 minutes have passed since the power was turned on.
[0024]
The gas detection device shown in FIG. 1 immediately changes the CO alarm state without the CO 2 stage alarm delay time and the CO alarm release time in order to facilitate the CO alarm and the alarm release within about 25 minutes after the power is turned on. It is characterized by doing so.
[0025]
In the gas detection apparatus shown in FIG. 1, the gas sensor 1 has a heater 2 and a sensor element 3. The central processing unit (CPU) 11 alternately outputs a heater driving signal for a low temperature region voltage 0.2V and a high temperature region voltage 0.9V heater driving signal for driving the heater 2 to the transistor Tr1.
[0026]
The transistor Tr1 is turned off by the heater driving signal for the low temperature region voltage 0.2V, the potential of the resistor R4 is set to about 0.2V, and the transistor Tr1 is turned on by the heater driving signal for the high temperature region voltage 0.9V. The resistor R2 is short-circuited to set the potential of the resistor R4 to about 0.9V.
[0027]
The integrated circuit IC1 inputs the potential of the resistor R4 to the non-inverting input terminal, inputs the potential of the gas sensor 1 to the inverting input terminal, and outputs an L level to the transistor Tr2 when the potential of the resistor R4 is about 0.2V. When the potential of the resistor R4 is about 0.9V, the transistor Tr2 outputs an H level.
[0028]
The transistor Tr2 and the resistor R5 constitute a heater driving unit 5 that drives the heater 2 inside the gas sensor 1. The transistor Tr2 sets the heater temperature to a low temperature range by flowing a relatively small current through the heater 2 according to the L level inputted when the potential of the resistor R4 is about 0.2V, and the potential of the resistor R4 is about 0.9V. The heater temperature is set to a high temperature range by causing a relatively large current to flow through the heater 2 according to the H level input at the time.
[0029]
For this reason, as shown in FIG. 2, the CPU 11 periodically changes the temperature of the gas sensor 1 between a low temperature region (100 ° C.) and a high temperature region (400 ° C.). Further, the CPU 11 maintains the sensor temperature of 100 ° C. for 15 seconds in the low temperature range, and detects the gas concentration of carbon monoxide by the gas sensor input from the sensor element 3 at the CO detection point (black circle in FIG. 2). In the high temperature range, the sensor temperature is maintained at 400 ° C. for 5 seconds, and the concentration of methane gas is detected at the methane detection point (black circle in FIG. 2).
[0030]
According to this gas detector, the period of the CO detection point is 20 seconds, which is significantly shorter than the conventional 150 seconds.
[0031]
Further, the CPU 11 outputs a detection resistance drive signal to the transistor Tr3, and turns on / off the transistor Tr3. When the transistor Tr3 is off, the resistance connected to the gas sensor 1 is only R6. When the transistor Tr3 is on, the resistance connected to the gas sensor 1 is a parallel resistance of R6 and R7.
[0032]
Further, a resistor R12, a volume VR, and a resistor R13 connected in series are provided between the power source Vcc and the ground, and the CO set point (CO 1 stage alarm point) input is taken into the CPU 11 from the volume VR. Yes. A resistor R11 and a thermistor TH1 connected in series are provided between the power supply Vcc and the ground, and the thermistor input is taken into the CPU 11 from the thermistor TH1.
[0033]
Further, the CPU 11 is connected with a speaker 19 as an alarm device that notifies an alarm indicating an abnormality in the gas concentration of a gas such as carbon monoxide or methane. In addition, the gas detection device includes an LED 21a indicating ON / OFF of the power source, an LED 21b indicating an alarm of an abnormal carbon monoxide gas concentration, and an LED 21c notifying an alarm indicating an abnormal methane gas concentration.
[0034]
The CPU 11 is configured to notify the speaker 19 of an alarm indicating an abnormality in the methane gas concentration when the methane gas concentration becomes equal to or higher than the second-stage alarm point that is larger than the first-stage alarm point.
[0035]
The CPU 11 includes an alarm point determination unit 13, a timer 15, and an alarm delay control unit 17. The alarm point determination unit 13 determines whether the CO gas concentration is equal to or higher than the first-stage alarm point, and determines whether the CO gas concentration is equal to or higher than the second-stage alarm point.
[0036]
The alarm delay control unit 17 notifies the first alarm when the CO gas concentration becomes equal to or higher than the first alarm point, and the CO gas concentration becomes equal to or higher than the second alarm point greater than the first alarm point. At this time, a second alarm is notified.
[0037]
The timer 15 manages a certain time. Based on the time information from the timer 15, the alarm delay control unit 17 indicates that when 25 minutes have elapsed since the power was turned on, when 13 minutes have elapsed since the CO gas concentration became the first alarm point or higher. A first alarm is notified, and a second alarm is notified when the CO gas concentration reaches or exceeds the second-stage alarm point.
[0038]
Further, the alarm delay control unit 17 notifies the first alarm when 13 minutes have elapsed from when the CO gas concentration has reached or exceeded the first stage alarm point after 25 minutes have elapsed since the power was turned on, and the CO gas concentration The second alarm is notified when 3 minutes elapses from when the second alarm point becomes higher than the second alarm point. That is, the alarm delay time is set in order to respond to a false alarm prevention request for a CO gas concentration alarm from the user.
[0039]
Next, the operation of the gas detection apparatus of the embodiment configured as described above, that is, the gas detection method will be described with reference to the flowcharts shown in FIGS. 3 to 9 and the timing charts of FIGS.
[0040]
First, when the time is 30 ms before the end of heat-down (YES in step S11), the CPU 11 determines the CO set point A /, which is the CO1 alarm point (first alarm point) according to the potential in the volume VR. The D input is captured (step S13), the thermistor A / D input is captured by the potential of the thermistor TH1 (step S15), and the gas sensor A / D input is captured from the gas sensor 1 (step S17).
[0041]
Next, the CPU 11 calculates a CO resistance value based on the captured gas sensor A / D input (step S19), calculates a CO temperature correction coefficient based on the thermistor A / D input (step S21), and calculates the calculated CO temperature. Temperature correction is performed on the CO resistance value using the correction coefficient (step S23). Further, a CO voltage value is calculated based on the temperature-corrected CO resistance value (step S25), and a CO second alarm point (second alarm point) is calculated based on the CO set point A / D input (step S27).
[0042]
Thereafter, the CO alarm determination during the inspection mode is performed (step S29). That is, in the time less than 25 minutes after the power is turned on, the inspection mode process of the flowchart shown in FIG. 4 is performed. Note that the processing in the inspection mode is performed according to the timing chart of FIG.
[0043]
First, the alarm point determination unit 13 determines whether the CO voltage value (voltage corresponding to the CO gas concentration) exceeds the CO2 stage alarm point (step S101), and the CO voltage value exceeds the CO2 stage alarm point. If not, it is determined whether the CO voltage value exceeds the C01 stage alarm point (step S103). If the CO voltage value does not exceed the C01 stage alarm point, the process waits (step S105) and proceeds to step S115.
[0044]
On the other hand, when the CO voltage value exceeds the CO1 stage alarm point, the alarm delay control unit 17 determines whether or not the state exceeding the CO1 stage alarm point continues for 13 minutes (step S107). When the exceeding state continues for 13 minutes, a warning is given after a delay of CO1 stage (step S109), and the process proceeds to step S115. If the exceeding state has not continued for 13 minutes, a CO1 stage delay warning is issued (step S111), and the process proceeds to step S115.
[0045]
In the alarm after the delay of the CO1 stage, perform an incomplete combustion alarm and repeat “Pipppippippo” “Air is dirty and dangerous. Open the window and ventilate”.
[0046]
In step S101, if the CO voltage value is greater than or equal to the CO2 stage alarm point, the alarm delay control unit 17 performs an alarm after the CO2 stage delay (step S113), and proceeds to step S115.
[0047]
As with the post-CO2 delay alarm, an incomplete combustion alarm is issued and repeated “Pippoppippo” “Air is dirty and dangerous. Open the window and ventilate”. In step S115, it is determined whether or not 25 minutes have elapsed since the power was turned on (step S115). If 25 minutes have elapsed, the inspection mode is terminated.
[0048]
When the processing in the inspection mode is completed, the process returns to the flowchart of FIG. 3 to determine whether or not the state is the post-CO2 stage delay state (step S31), and when the state is the post-CO2 stage delay state, the CO voltage value is CO1. It is determined whether or not the step release point is exceeded (step S121). In addition, after completion | finish of the process of inspection mode, it carries out according to the time chart of FIG. If the CO voltage value is below the CO1 stage release point, it is determined whether the state below the release point has continued twice (step S123), and the state below the release point has continued twice. In the case, it waits (step S125) and returns to step S11 .
[0049]
On the other hand, if the CO voltage value exceeds the CO1 stage release point in step S121, or if the state below the release point does not continue twice in step S123, the process immediately returns to step S11 .
[0050]
Next, in step S31, when the state is not the state after the CO2 stage delay, it is determined whether or not the state is the CO2 stage delay state (step S33). It is determined whether or not the value exceeds the CO2 alarm level (step S131).
[0051]
If the CO voltage value exceeds the CO2 stage alarm point , it is determined whether or not the exceeding state continues for 3 minutes (step S133). If the exceeding state continues for 3 minutes, the CO2 stage is determined. An alarm after delay is performed (step S135), and the process returns to step S11 . If the exceeding state does not continue for 3 minutes, the process returns to step S11 without performing the alarm after the CO2 stage delay.
[0052]
On the other hand, if the CO voltage value does not exceed the CO2 stage alarm point in step S131, it is determined whether the CO voltage value exceeds the CO1 stage release point (step S137), and the CO voltage value is released from the CO1 stage. If it is below the release point, it is determined whether or not the state below the release point is continued twice (step S139) . If the state below the release point is continued twice, it waits ( Step S140) and return to Step S11 .
[0053]
If the CO voltage value exceeds the CO1 stage release point in step S137, or if the state below the release point does not continue twice in step S139, the process immediately returns to step S11 .
[0054]
Next, in step S33, if the state is not in the CO2 stage delay state, it is determined whether the state is the CO1 stage delay state (step S35). If the state is after the CO1 stage delay, the CO voltage is determined. It is determined whether or not the value exceeds the CO2 stage alarm point (step S141). If the CO voltage value exceeds the CO2 stage alarm point performs an alarm after CO2 stage delay (step S143), the flow returns to step S11.
[0055]
On the other hand, if the CO voltage value does not exceed the CO2 stage alarm point in step S141, it is determined whether the CO voltage value exceeds the CO1 stage release point (step S145), and the CO voltage value is released to the CO1 stage release point. If it is below the release point, it is determined whether or not the state below the release point is continued twice (step S147) . If the state below the release point is continued twice, it waits ( Step S149), the process returns to step S11 .
[0056]
If the CO voltage value exceeds the CO1 stage release point at step S145, or if the state below the release point does not continue twice at step S147, the process immediately returns to step S11 .
[0057]
Next, in step S35, if the state is not the state after the CO1 stage delay, it is determined whether the state is in the CO1 stage delay state (step S37). If the state is in the CO1 stage delay state, the CO voltage is determined. It is determined whether or not the value exceeds the CO2 stage alarm point (step S151).
[0058]
If the CO voltage value does not exceed the CO2 stage alarm point, it is determined whether the CO voltage value is below the CO1 stage release point (step S153), and the CO voltage value is below the CO1 stage release point. Is determined whether or not the state below the release point continues twice (step S155), and when the state below the release point continues twice, it waits (step S157) and step S11. Return to.
[0059]
On the other hand, in step S153, if the CO voltage value exceeds the CO1-stage release point, beyond the state that it is determined whether to continue 13 minutes (step S159), beyond which conditions 13 minutes continuously When this is done, an alarm is given after a delay of CO1 stage (step S161), and the process returns to step S11 . Also, if beyond that state does not continue 13 minutes, immediately returns to step S11.
[0060]
In step S37, if the state is during the CO1 stage delay, it is determined whether the CO voltage value exceeds the CO2 stage alarm point (step S171). If the CO voltage value does not exceed the CO2 stage alarm point, it is determined whether the CO voltage value exceeds the CO1 stage alarm point (step S173).
[0061]
If the CO voltage value exceeds the CO1 stage alarm point, a CO1 stage delay alarm is issued (step S175), and the process returns to step S11 . If the CO voltage value does not exceed the CO1 stage alarm point, the process immediately returns to step S11 . When the CO voltage value exceeds the CO2 stage alarm point, a CO2 stage delay alarm is issued (step S177), and the process returns to step S11 .
[0062]
As shown in FIG. 10 and FIG. 11, the methane gas abnormality alarm is notified by an audible alarm when the methane voltage value corresponding to the methane gas concentration exceeds the second stage alarm point. . In this alarm, a city gas alarm is performed, and “pip pip pip” “has gas leaked” is repeated.
[0063]
As described above, according to the gas detection device of the embodiment, the gas sensor 1 that detects CO and methane becomes a CO detection point in a cycle of 20 seconds, so that the CO inspection can be performed in a short time without using the inspection cover. Yes.
[0064]
Further, the alarm delay control unit 17 immediately notifies an alarm when the CO voltage value exceeds the CO2 stage alarm point 25 minutes before the power is turned on, and the CO voltage value becomes 25 minutes after the power is turned on. The first alarm is notified when 13 minutes have elapsed from when the CO1 level alarm point is exceeded, and the second alarm is notified when 3 minutes have elapsed since the CO voltage value has exceeded the CO2 level alarm point. To do.
[0065]
In other words, the contractor installs the gas detection device and performs the CO inspection within 25 minutes after the power is turned on. However, the CO inspection is simplified because the alarm is immediately notified when the CO voltage value exceeds the CO2 alarm level. This can be done in a short time, thereby reducing the work burden on the contractor.
[0066]
In addition, after 25 minutes have passed since the power was turned on, the alarm delay time of 13 minutes for the first stage and the alarm delay time of 3 minutes for the second stage, etc. are set, so that the CO gas concentration abnormality alarm can be set. Misinformation can be prevented.
[0067]
Note that the present invention is not limited to the gas detection method and gas detection apparatus of the above-described embodiment. In the embodiment, the predetermined time is about 25 minutes after the power is turned on, but the predetermined time is not limited to 25 minutes, and other time may be set.
[0068]
In the embodiment, 13 minutes and 3 minutes are set as the alarm delay time. However, the present invention is not limited to this, and other time may be set as the alarm delay time. In addition, it is needless to say that various modifications can be made without departing from the technical idea of the present invention.
[0069]
【The invention's effect】
The invention of claim 1, according to the second aspect of the invention, when the power is turned on during the inspection mode of the first gas concentration in the first before the predetermined time has elapsed became the first gas concentration first stage or alarm point The first alarm is notified when the second predetermined time elapses, and the second alarm is notified when the first gas concentration is equal to or higher than the second-stage alarm point . In other words, a false alarm can be prevented by delaying the first alarm in the inspection mode, and the second alarm is immediately notified when the first gas concentration exceeds the second stage alarm point. The CO inspection can be performed easily in a short time without using. Further, after the first predetermined time has elapsed since the power was turned on, the first alarm is notified when the third predetermined time has elapsed since the first gas concentration has reached or exceeded the first stage alarm point, and the first gas concentration is 2 The second alarm is notified when the fourth predetermined time has elapsed since the stage alarm point was reached. That is, by setting the alarm delay time, it is possible to prevent the false alarm of the first gas concentration abnormality alarm.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of a gas detection device according to an embodiment of the present invention.
FIG. 2 is a timing chart of the temperature of the gas sensor in the gas detection device of the embodiment.
FIG. 3 is a flowchart for explaining a gas detection method realized by the gas detection device of the embodiment;
4 is a flowchart for explaining CO alarm determination during an inspection mode in the gas detection method of FIG. 3; FIG.
FIG. 5 is a flowchart for explaining processing when the state after delay of CO2 stage is YES in the gas detection method of FIG. 3;
6 is a flowchart for explaining a process when a CO2 stage delay state is YES in the gas detection method of FIG. 3;
7 is a flowchart for explaining a process when the state after the delay of the first CO stage in the gas detection method of FIG. 3 is YES.
FIG. 8 is a flowchart for explaining processing when the CO1 stage delay state is YES in the gas detection method of FIG. 3;
9 is a flowchart for explaining processing when the CO1 stage delay state is NO in the gas detection method of FIG. 3;
FIG. 10 is a timing chart in an inspection mode of less than 25 minutes after power is turned on.
FIG. 11 is a timing chart in a normal mode after 25 minutes have elapsed since power-on.
FIG. 12 is a timing chart of the temperature of the gas sensor in the conventional gas detection device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Heater 3 Sensor element 5 Heater drive part 11 CPU
13 Alarm point determination part 15 Timer 17 Alarm delay control part 19 Speaker 21a, 21b, 21c LED
Tr1 Transistor TH1 Thermistor IC1 Integrated circuit VR Volume

Claims (2)

The temperature of the gas sensor is alternately changed periodically between a low temperature region and a high temperature region, the first gas concentration is detected in the low temperature region, the second gas concentration is detected in the high temperature region, and the first gas concentration is the first gas alarm point. The first gas alarm indicating the abnormality of the first gas concentration is notified when the above becomes the second gas alarm indicating the abnormality of the second gas concentration when the second gas concentration becomes equal to or higher than the second gas alarm point. In the gas detection device for informing
Said from power before elapse the first predetermined time during the first inspection mode gas concentration second predetermined time when the first gas concentration becomes 1 stage or alarm point in the first gas alarm point When the time elapses, a first alarm is notified, and a second alarm is notified when the first gas concentration is equal to or higher than the second stage alarm point that is greater than the first stage alarm point at the first gas alarm point. , wherein the application of power after the first predetermined time to inform the first alarm when the elapsed third predetermined time from when the first gas concentration becomes the first stage or alarm point, the first A gas detection device comprising: an alarm delay control means for notifying the second alarm when a fourth predetermined time has elapsed from when one gas concentration becomes equal to or higher than the second-stage alarm point . The temperature of the gas sensor is alternately changed periodically between a low temperature region and a high temperature region, the first gas concentration is detected in the low temperature region, the second gas concentration is detected in the high temperature region, and the first gas concentration is the first gas alarm point. The first gas alarm indicating the abnormality of the first gas concentration is notified when the above becomes the second gas alarm indicating the abnormality of the second gas concentration when the second gas concentration becomes equal to or higher than the second gas alarm point. A gas detection method for notifying
Said from power before elapse the first predetermined time during the first inspection mode gas concentration second predetermined time when the first gas concentration becomes 1 stage or alarm point in the first gas alarm point When the time elapses, a first alarm is notified, and a second alarm is notified when the first gas concentration is equal to or higher than the second stage alarm point that is greater than the first stage alarm point at the first gas alarm point. , wherein the application of power after the first predetermined time to inform the first alarm when the elapsed third predetermined time from when the first gas concentration becomes the first stage or alarm point, the first A gas detection method comprising: an alarm delay control step of notifying the second alarm when a fourth predetermined time has elapsed from when one gas concentration becomes equal to or higher than the second-stage alarm point .

Images