JPH08249565A - Gas leak alarm - Google Patents

Abstract

PURPOSE: To provide a multifunctional gas leak alarm which can also deal with the terminal equipment of an alarm system with a simplified hardware. CONSTITUTION: This device is constituted by combining a gas detection part 1 for outputting a signal while reacting to gas, warning part 5, microcomputer 8 as a control means provided with a non-volatile memory 9, communication circuit 10 for exchanging data with an external device such as the centralized monitor panel of the alarm system, and power source circuit combining a constant voltage circuit 7 and a constant current circuit 11. Then, respective functions such as the reading of a sensor signal output with a reference gas concentration, storage into a memory, the setting of a warning operation level based on that memory value, the judgement and output of necessity for warning operation and centralized monitor with the alarm system by a communication transmission system are executed on the program of the microcomputer 8 in the manner of software.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects gas leaks such as city gas and propane gas, or CO gas generated due to incomplete combustion of gas equipment, and when the gas concentration rises above a predetermined level. The present invention relates to a gas leak alarm device that issues an alarm.

[0002]

2. Description of the Related Art Various gas leak alarms and gas detectors have been conventionally used for detecting gas leaks such as city gas and propane gas, or for detecting gas such as CO gas generated due to incomplete combustion of gas equipment. Developed and commercialized. Here, a circuit configuration of a conventional gas leak alarm device is shown in FIG. 11 by taking a gas leak alarm device employing a catalytic combustion gas sensor as an example.
Shown in In the figure, 1 is a gas detection element GS, a compensation element (for temperature compensation) TC, a fixed resistance R, a gas detection section (gas sensor) in which a fixed resistance R and a variable resistance VR are assembled, 2 is an amplification circuit, and 3 is a pre-alarm. (1st stage), and a level comparison circuit provided with 2 stages of comparators Comp1, Comp2 for alarm (2nd stage), 4 is a control circuit (eg LSI), 5
Is an alarm unit equipped with an indicator lamp, speaker / buzzer, etc.
Reference numeral 6 is an alarm output circuit for transmitting an alarm signal to an external device such as a centralized monitoring panel, and 7 is a constant voltage circuit of a power supply, which are unitized to form a gas leak alarm device. In addition, in this example, the catalytic combustion type is illustrated as the gas sensor, but other types such as a semiconductor type and a hot wire semiconductor type are known. It is also known that one gas leak alarm device incorporates, for example, a city gas or propane sensor and a CO gas sensor together.

The operation of such a gas leak alarm device is well known, and gas leak such as city gas occurs and gas detector element GS is generated.
When the gas reacts (combusts) with the leak gas, the element temperature rises due to the reaction heat and the electric resistance value increases, and a sensor signal of a level proportional to the gas concentration is output from the bridge circuit of the gas detection unit 1. This sensor output is signal-amplified by the amplifier circuit 2, and then the comparator Co
The necessity of alarm is judged by comparing with each operation setting value set in advance in mp1 and Comp2. Here, the control unit 4 blinks the display lamp of the alarm unit 5 with the output of the comparator Comp1 of the first stage to call attention, and when the leak gas concentration further increases and exceeds the set level of the comparator Comp2 of the second stage, In addition to blinking the display lamp, an alarm is issued to the surroundings by a speaker, a buzzer, etc., and this alarm output is transmitted via an output circuit 6 to a gas meter with a gas shutoff valve, a centralized monitoring panel of a disaster prevention system, and the like.

[0004]

By the way, the above-described conventional gas leak alarm has the following problems in function and other aspects. That is, 1) In the conventional gas leak alarm device, many adjustment circuits including the sensitivity adjustment volume of the gas sensor, the zero point adjustment of the gas detection unit, the amplification degree adjustment, etc. are required, and therefore the circuit in terms of hardware. The configuration becomes complicated, which is a major factor in increasing the manufacturing cost and the adjustment cost.

2) CO compared to combustion gas such as methane
The gas is difficult to burn, and the sensor output level of CO gas in the catalytic combustion type gas sensor is a value that is about one digit lower than that of methane gas. Further, since the gas leak alarm device has a specified service life that can be continuously used for at least about 5 years, the gas sensor will change over time and drift during long-term use. For this reason, the S / N ratio between the drift signal and the sensor output signal level is greatly reduced in the CO gas sensor, and there is a problem in that a malfunction occurs and an alarm is issued even though the gas concentration level is low. How to prevent the decrease of the ratio and how to realize the cancellation of the drift component in the signal processing are major problems.

3) A conventional gas leak alarm device is known which has an output section for transmitting an operation signal for gas leak detection to the outside. Its function is, for example, in addition to the above-mentioned alarm output. It is limited to issuing an alarm when the power of the alarm device is turned off, and does not have a function of changing the operating conditions of the gas leak alarm device by inputting from a centralized monitoring panel of an external device.

4) The conventional gas leak alarm device determines whether or not the gas concentration of the detected gas has reached a dangerous level and issues an alarm. What is the gas concentration below the level at which the alarm is generated? I do not know if there is such a situation. On the other hand, it is known that CO gas generated by incomplete combustion of gas equipment has a slight adverse effect on the human body even at a relatively low level, and the gas concentration can be detected as necessary even in a steady state below the alarm level. Detailed countermeasures are required.

5) The gas sensor must be preheated to a high temperature of about 150 ° C. for CO gas and about 350 ° C. for methane gas in order to react with the detection gas. In this case, it does not become a hindrance when used in a normal room, but when detecting incomplete combustion gas (CO etc.) contained in the combustion exhaust gas of a gas device, the temperature characteristic is large because the ambient temperature change of the gas sensor is large. However, there is no conventional gas leakage alarm device having such a function, and it is also an issue to realize it by a simple means.

6) In order to confirm the output level and the operation set value of the gas sensor, the conventional gas leak alarm is placed in an atmosphere having a standard gas concentration, and the gas is detected so that an alarm is issued in this state. The sensitivity volume of the section is adjusted manually, but this adjustment work requires time and money, and a countermeasure is required.

7) In promoting the multi-functionalization of the gas leak alarm device in combination with an external alarm system, how to centrally monitor the data of the gas leak alarm device by the transmission method and set / reset various modes related to the alarm. It is also one of the challenges to realize it easily. The present invention has been made in view of the above points, and an object of the present invention is to provide a multifunctional gas leak alarm that can meet the above-mentioned problems.

[0011]

In order to achieve the above object, according to the present invention, a gas leak alarm is provided with the following functions. 1) A combination of a gas sensor that outputs a signal in response to gas, an alarm unit, a control unit having a non-volatile memory, and a power supply circuit. The gas concentration level at which an alarm is issued is stored in the memory as an operation set value. The control means stores the stored value, compares the set value with the sensor output, and determines whether or not the alarm operation is necessary.

2) A microcomputer is adopted as the control means. 3) A function that reads the sensor signal output at the reference gas concentration, stores it in the memory, sets the alarm operation level based on the memory value, and determines whether or not the alarm operation is required during the execution of the program of the microcomputer. Have. 4) A communication unit having a function of setting an operation mode with an external device, receiving judgment data of an alarm operation, and designation data of an output unit is provided.

5) It is provided with a function of steadily transmitting the gas detection operation status and the signal level of the gas sensor with an external device through the communication means. 6) An ambient temperature sensor for detecting the ambient temperature of the gas sensor is provided, and a function to programmatically correct the sensor output according to the temperature characteristic of the sensor based on the temperature signal is provided.

7) It has a function of determining the zero drift output level of the sensor and correcting the drift of the sensor signal. 8) Using the gas leak alarm equipped with the functions of the above items, the gas concentration of the incomplete combustion gas contained in the exhaust gas of the gas equipment is detected.

[0015]

With the above construction, the gas leak alarm device performs its function as described below to perform gas leak detection and alarm operation. 1) Storing the sensor output signal in a non-volatile memory when the gas leak alarm is in a steady state without methane, CO gas, etc. and in an atmosphere of a reference gas concentration,
The microcomputer as the control means calculates the sensor sensitivity of the gas sensor and sets the alarm operation level in the process of executing the program. As a result, the hardware for manually setting the sensor sensitivity and mode can be omitted, and the circuit configuration can be simplified.

2) Further, when the level of the alarm operation is set in the environment of the reference gas concentration in the above item 1), a setting mode switch is provided in the microcomputer or an external command is issued via a communication means described later. The sensor output level at that time is stored in the non-volatile memory. 3) When the alarm for the detected gas is divided into the first-stage pre-alarm and the second-stage danger alarm, the gas concentration level setting of each stage is executed on the program of the microcomputer. Then, when a gas leak is actually detected, the sensor sensitivity that has been read in the memory in advance,
The comparison between the alarm operation set value and the sensor signal level is executed on the program of the microcomputer, and the necessity of alarm output is determined based on the result.

4) Further, writing of the above-mentioned various data to the memory, setting / resetting of various modes required by the program of the microcomputer, an alarm operation signal, and a sensor output corresponding to the gas concentration read in the steady state. If necessary, the value can be transmitted to an external device such as a centralized monitoring panel of the alarm system through a communication means provided in the gas leak alarm so that the gas leak alarm can be easily systemized.

5) Since the gas sensor has a temperature characteristic in which the output changes according to the change of the ambient temperature, by providing the ambient temperature sensor, the temperature correction of the sensor output signal as a function of the ambient temperature level detected by the sensor is performed by the microcomputer. It can be done automatically on the program. 6) Further, when setting the alarm operation level in the environment of the reference gas concentration, the microcomputer is provided with a setting mode switch or is input from an external device through the above-mentioned communication means, and the program of the microcomputer is used. Then, the sensor output level at that time can be easily dealt with by storing it in the nonvolatile memory.

7) Determination of sensor drift output level,
And the drift correction function is executed as follows. That is, since the gas sensitivity of the catalytic combustion type gas sensor changes depending on the heating temperature of the sensor, first the temperature of the sensor is periodically lowered to a state where the gas sensitivity is almost zero, and in this state, the zero drift signal is read from the sensor output. Store in non-volatile memory. Then, when the gas sensor is preheated again to return to the steady state, the output signal of the gas sensor is drift-corrected by adding the drift signal.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings of each embodiment, the same members corresponding to FIG. 11 are denoted by the same reference numerals. FIG. 1 is a circuit configuration diagram of a gas leak alarm for one sensor, and the gas leak alarm is shown in FIG.
Similar to 1, the contact combustion type gas detection element GS and the compensating element T
A gas detection unit (gas sensor) 1, an amplifier circuit 2, an alarm unit 5, a constant voltage circuit 7 configured by a bridge circuit including C, a microcomputer 8 as a general control unit, and a non-volatile memory attached to the microcomputer 8 ( For example, EE
(PROM) 9, a communication circuit 10, a constant current circuit 11 connected to a power supply circuit of the gas detection unit 1, and a setting mode switch 12 in combination.

With such a configuration, in a steady state where no gas leaks, the variable resistor VR is adjusted so that the bridge output of the gas detector 1 becomes zero as an initial setting. Further, it is necessary to control the energization so that the sensor of the gas detection unit 1 is preheated to a temperature at which it easily reacts with the gas to be detected in a steady state, for example, about 350 ° C. for methane gas and about 150 ° C. for CO gas. The sensitivity characteristics of the sensor for methane gas and CO gas are shown in FIG. Therefore, in the embodiment of FIG. 1, the constant voltage circuit 7 and the constant current circuit 11 are used together as the power supply circuit.

That is, in the power feeding system using only the constant voltage circuit 7, the shared voltage applied to the series circuit of the gas detecting element GS and the compensating element TC of the gas detecting section 1 is the resistance value of the element even in the steady state without gas leakage. Dependently, the element on the high partial pressure side also increases in temperature, and as a result, the resistance value of the element increases more and more, and the partial pressure also becomes higher, which causes the drift. In this respect, by using the constant voltage circuit 7 and the constant current circuit 11 together, the drift caused by the change in the shared voltage as described above can be avoided.

Further, as a method of supplying power to the gas detection unit 1 when the constant current circuit 11 is also used, FIGS.
It can be implemented by the method shown in. Here, (a) is a constant current energization method in which a current is continuously supplied, (b) and (c) are pulse energization methods in which a current is intermittently supplied, and (c) is a point of time when the power is turned on with a large pulse width. In this example, the sensor preheating is rapidly performed in a short time. Each energization method is executed by ON / OFF controlling the constant current circuit 11 according to the mode set on the program of the microcomputer 8.

The output signal of the gas detector 1 is amplified by the amplifier circuit 2 and then input to the A / D conversion port of the microcomputer 8. Then, the A / D converted signal is written in the non-volatile memory 9 of the microcomputer 8 by a command given to the setting mode switch 12, and the set value corresponding to the reference gas concentration is determined as described below. That is, when the setting mode switch 12 is turned on in a state where the gas leak alarm device is placed in a gas atmosphere having a reference gas concentration (for example, 3000 ppm) close to the alarm level, the output signal of the gas detection unit 1 is A / D converted. Then, it is written in the non-volatile memory 9 as a digital value. The sensor output value at this reference gas concentration is stored in memory for each type of detection gas and sensor. As a result, the memory value at the reference gas concentration is set to 100%, the operation set value of the first step (pre-alarm) is set to 40%, and the operation set value of the second step (danger alarm) is set to 80%. The algorithm can be easily determined.

When the setting mode switch 12 is turned off after the writing of the operation set value in the memory is completed, the normal gas leak monitoring mode is entered. In this monitoring mode, the output level of the gas detector 1 and the set value stored in the memory are compared on a program of the microcomputer 8 (the details of this program function will be described later) to monitor the presence or absence of gas leakage. The necessity of alarm is determined according to the gas concentration level. Here, when the detected gas concentration exceeds the pre-alarm level of the first step, the detection operation is repeated several times and then the display lamp of the alarm unit 5 is made to blink, and the second step of the alarm level is further raised. When it exceeds, an alarm will be issued by voice, buzzer sound, etc.,
An alarm signal is transmitted to an external centralized monitoring board or the like through the communication circuit 10.

In this case, according to the present invention, the communication circuit 1
0 is not limited to the above-mentioned alarm signal transmission function,
It also has the following functions. That is, a) sensor output in a steady state, that is, transmission of gas concentration level measured by a gas leak alarm device b) external setting / resetting of a setting mode signal corresponding to ON operation of the setting mode switch 12 c) external device Setting of alarm operation level value from d) When multiple gas sensors are installed side by side, level set for each sensor and operation check e) Set of temperature correction function to be described later f) Various data required by other microcomputers Transmission of these is executed on the program of the microcomputer 8 described later. In this way, by providing the above-mentioned function to the communication means with the outside, a multifunctional gas leak alarm can be manufactured with simple hardware at low cost, and the gas leak alarm can be used to monitor the gas concentration quantitatively. It can also be used as a terminal of a gas detection system.

FIG. 2 shows an embodiment of a two-sensor gas leak alarm equipped with two sets of gas detectors 1-1 and 1-2 for methane gas and CO gas as gas detectors.
Each of the gas detectors 1-1 and 1-2 is individually equipped with an amplifier circuit 2-1, 2-2,
Constant current circuit 11-1, 11-2, setting mode switch 12-
1, 12-2 are provided and are connected to the same power source via a common constant voltage circuit 7. In this case, each gas detector 1
A large merit can be obtained by adopting the pulse energization method described in FIGS. 5B and 5C for supplying power to -1, 1-2. That is, as described above, when the gas sensor is preheated, the sensor temperature of methane gas (350 ° C.) and the sensor temperature of CO gas (150 ° C.) are greatly different, and therefore the same constant voltage circuit 7 simply supplies power. However, it is difficult to control the temperature individually. In this regard, the constant current circuits 11-1 and 11-2 are individually attached, and the pulse width for supplying electricity to the gas detection units 1-1 and 1-2 by the pulse energization method is individually adjusted according to the sensor temperature. By doing so, the sensor temperature can be easily and properly controlled.

Further, the embodiment shown in FIG. 2 is equipped with an ambient temperature sensor 13. Then, the detection signal of the temperature sensor 13 is read, and the signal is used as a function to correspond to the temperature characteristics of the sensor shown in FIG.
The temperature of the output signal is corrected. This correction is executed on the program of the microcomputer 8.

The gas detecting element employed in the gas detecting section 1 is not limited to the catalytic combustion type gas sensor,
A semiconductor gas sensor can also be used and its configuration is shown in FIG.
Shown in This semiconductor type sensor is composed of a combination of a SnO ₂ element 14 and a heater 15. When the ambient gas concentration changes, the resistance value of the SnO ₂ element 14 itself changes correspondingly and the sensor output changes.

Next, the program structure of the microcomputer 8 for executing the above-mentioned functions will be described with reference to the flowchart of FIG. When the power is turned enters the power-on, step S ₁ to S ₃₃ of a program to be described below
To execute. It should be noted that in the figure, the routes indicated by the thick lines indicate the execution routes that are always operating, and the thin lines other than the thick lines indicate the routes when a specific function such as the setting mode is executed.

1) In step S ₁ , the registers and the like in the microcomputer are reset, and the data stored in the memory and the control program data are checked for any abnormality. Furthermore, the sensor of the gas detector is heated to start sensor temperature control ₍₀₎ (preheat). While 2) sensor after Step S ₂ at power-up so as not proceed to the next step until heated to a predetermined temperature, performing the temperature control of the sensor ₍₀₎ in step S _3. This is because if the heat balance between the gas detection element GS and the compensating element TC is unbalanced during the process of increasing the sensor temperature, a drift signal may be temporarily output from the gas detection unit and malfunction may occur. This is to prevent it.

3) When the temperature of the sensor rises to a predetermined temperature after the preheating time has passed, the process proceeds to step S ₄ . Here, the sensor output signal is amplified, A / D converted and read, and the value is stored in the memory. Here, when the power supply to the gas detection unit 1 is performed by the pulse energization method described above, the A / D
It is necessary to read the converted value in synchronization with the pulse energization width, but in this case it is not necessary to complete the reading in one operation, and the sensor output signal is A / D converted for each pulse. There is also a method of obtaining the average value for the n times and storing it in the memory.

Further, in step S ₄ , various signals are read into the microcomputer. Furthermore, if an ambient temperature sensor (see Fig. 2) is provided, the signal level of that sensor is also read, and the actual gas concentration level is calculated by performing temperature correction based on the output level of the gas sensor and the ambient temperature measurement value that were read previously. Calculate and store the value as the gas concentration. If the gas leak alarm has two sets of gas sensors, step S ₄ is executed for each sensor.

4) Step S ₅ is a determination section for determining whether or not the operation of measuring the sensor sensitivity to the reference gas concentration and writing it in the memory is performed. Here, it if necessary to specially change the temperature of the sensor is performed in step S _7, further temperature control to preheat the sensor to fit the set temperature ₍₁₎
After that, the gas and, if necessary, the ambient temperature control signal are A / D converted and read into the memory. This reading does not have to be performed once, and n can be used to reduce the error.
It is also possible to measure the number of times, obtain the average value thereof, and then write the average value in the memory, and use that value as the reference sensitivity data of the gas sensor. When these settings mode is performed, proceeding by bypassing the step S ₆ to S ₁₇ for the next follow.

5) On the other hand, when the setting mode is not selected in step S ₅ , sensor temperature control ₍₂₎ is performed in step S ₆ . It should be noted that the bold line route shown in the figure circulates in a short time period, so that it is not necessary to be particular about the order of arrangement of the functional steps. 6) In step S _8, it determines whether the gas concentration level is above the value pre-alarm. Here, the reference gas sensitivity read in step S ₇ is compared with the value calculated as the pre-alarm level to determine whether or not the sensor output level is high in consideration of temperature correction. And the higher the sensor output level to set the alarm operation of the first row from been tested by the first-stage timer in step S _10.
In addition to considering the response time of the sensor to the gas, this timer time may cause false alarms due to the effects of temporary disturbances caused by other gases other than the detection gas (for example, flammable spray gas, alcohol vapor such as alcohol). It also plays a role in prevention. Further, the alarm of the first stage as described later in step S ₉ waits for the operating time of the recovery timer after having issued a predetermined time, executes the resetting of the alarm operation in step S _11.

[0036] 7) At S ₁₃ to S _17, a function of issuing a hazard alarm of the second stage in a further state of increased gas concentration level from the pre-alarm (first stage), the programmatic and the 1 It is executed similarly to the first stage. The first stage, 2
The set of stage alarm operation time performed in the memory of the microcomputer, the memory value is read in presence determination strains operation of step S _30, the display lamps, audio, a buzzer, an alarm operation such as an external signal Run.

8) In step S ₂₀ , the function mode of the gas leak alarm is changed if necessary. Note that when feature set mode is "present", until it receives the set data at step S ₂₃ is the basic to function in normal program mode (step S ₂₁₎ Since there is no data. Then, with respect to the reference gas sensitivity set in step S ₇ , the proportional coefficients K ₁ and K ₂ are determined in step S ₂₁ to determine the first and second steps.
Calculate the operation value of the stage. Note that the alarm can be subdivided into two or more stages and output. In contrast, the step, for example the proportional coefficient K _1, K ₂ values, the data received from the outside such as the temperature correction coefficients shown in step S _7, the mode when in step S ₂₂ sets the mode is "Yes" memory set at S _23. By providing this function, it is possible to change the operating condition of the gas leak alarm device (gas concentration at which an alarm is issued) as required by an external command (such as a centralized monitoring panel). For example, in a place with a high risk of fire, make the gas leak detection sensitivity sensitive, and in the place where alcohol, which easily reacts to the gas sensor, is used, conversely adjust the sensitivity to the insensitive side, or set a long timer time for operation confirmation. By suppressing the influence of miscellaneous gas, the malfunction of the gas leak alarm can be avoided.

9) Step S_{twenty four}Temperature compensation for sensor sensitivity with
Specify whether or not to perform step S _{twenty five}At ambient temperature
The temperature of the sensor sensitivity is corrected based on the sensor detection signal. What
Oh, step S_{twenty five}In addition to temperature compensation, humidity compensation (
Service characteristics change depending on the ambient humidity).
You can 10) Step S₂₆Then the drift correction function of the gas sensor
To execute. The sensor has aged resistance value during long-term use
The gas detector 1 shown in FIGS. 1 and 2 is changed to
The bridge circuit is out of balance and there is no gas leakage.
The sensor output appears even in the state and drifts (zero lift)
May occur. Especially the CO gas sensor has an output sensitivity
Because of its low output value and zero drift in response to CO gas
There is a risk that the value will be close and a false alarm will be generated. There
Then, in step S, the drift component is corrected.₂₇~
S₂₉To execute. First, step S₂₇, S₂₈By the figure
The sensor temperature based on the sensor temperature / sensor output characteristics shown in 8.
To a temperature where the sensor output becomes almost zero,
Step S₂₉In this state, the gas detector (bridge
Road), read the sensor signal output from the
Confirm the signal level of and set the value in the memory.

FIG. 9 is a diagram showing a model of the sensor temperature control performed for determining the above-mentioned zero drift, in which the correction timer is turned on and the sensor temperature is sufficiently lowered (the temperature at which the sensor does not react to gas). At this point, the zero drift signal is read at the point marked with a circle in the figure, and then the sensor temperature is recovered. In order to perform this temperature control in the embodiment of FIGS. 1 and 2, it is possible to realize it by supplying power to the gas detection unit by a pulse energization method as shown in FIG. That is, the energization pulse width is narrowed in the mode in which the sensor temperature is lowered, and the energization pulse width is widened in the mode in which the temperature is raised. Further, the time width of the correction timer ON is determined in consideration of the thermal response time characteristic of the sensor.

The correction timer is, for example, 1 every day.
The drift is corrected by operating once or once a week. Further, when the drift value is largely changed in comparison with the last time, is abnormally displayed in the following step S _30. 11) In step S ₃₀ to S _32, display output an alarm that has been set in step S _12, S _17, including the abnormal reading from the _memory, the audio / buzzer output, together to generate a like external signal output, external Signal output is the next step S
_{At 33,} it is transmitted to an external device.

[0041] 12) Step S ₃₃ the gas leakage alarm operation (warning, error), in addition to the transmission of gas concentration level,
It has the function of receiving set mode reset / set signals transmitted from an external device, alarm level set value set signals, and data required by the microcomputer. In addition to the gas meter with a gas shut-off valve, gas equipment for heating and hot water supply, external devices of the communication partner include a home automation control panel and a centralized monitoring panel for disaster prevention systems such as buildings. Various methods can be applied. When the step S ₃₃ is executed returns to step S _4, to perform the functions looping step S ₄ to S ₃₃ again.

[0042]

As described above, the present invention has the following effects. 1) The hardware is implemented by executing all the functions such as reading the output signal of the gas sensor, storing it in memory, setting and changing the alarm operation level, and setting various modes on the program of the microcomputer as the control means. A simplified gas leak alarm can be provided at low cost.

2) As compared with the conventional structure, adjustment by manual operation including sensor sensitivity and variations in amplifier can be omitted. 3) Since communication means for transmitting data to and from an external device is provided, set / reset of various modes required in the program of the microcomputer equipped in the alarm device, and further alarm operation signal, read at steady time The sensor output value or the like corresponding to the gas concentration can be transmitted to an external device such as a centralized monitoring panel of the alarm system through the communication means, which enables the alarm system to be supported.

4) By continuously outputting the gas concentration level detected by the gas sensor, the ambient gas concentration can be monitored even in a steady state below the alarm level. 5) By providing the ambient temperature sensor, the temperature of the sensor output signal can be automatically corrected on the program of the microcomputer as a function of the ambient temperature level detected by the sensor.

6) The zero drift signal of the sensor is read while the sensor temperature is lowered, and the zero drift correction of the sensor signal is performed on the program of the microcomputer so that the gas detection can be performed with high accuracy.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a gas leak alarm for one sensor according to an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a gas leak alarm for two sensors according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a semiconductor gas sensor.

FIG. 4 is a flowchart showing the program contents of the microcomputer in the embodiment of the present invention.

FIG. 5 is a model diagram of a power supply control method for the gas detection unit according to the embodiment of the present invention, in which (a) is a constant value energization method, (b),
(C) is a diagram showing a pulse energization method

FIG. 6 is a sensitivity characteristic diagram of a gas sensor showing a relationship between gas concentration and sensor output.

FIG. 7 is an ambient temperature characteristic diagram of a gas sensor showing the relationship between ambient temperature and sensor output.

FIG. 8 is a characteristic diagram showing a relationship between sensor temperature and sensor output.

FIG. 9 is an operation explanatory diagram of the zero drift correction timer according to the embodiment of the present invention.

FIG. 10 is a model diagram of sensor temperature control according to an embodiment of the present invention.

FIG. 11 is a circuit configuration diagram of a conventional gas leak alarm device.

[Explanation of symbols]

 1 Gas Detection Section 2 Amplification Circuit 5 Alarm Section 7 Constant Voltage Circuit 8 Microcomputer (Control Means) 9 Nonvolatile Memory 10 Communication Circuit 11 Constant Current Circuit 12 Setting Mode Switch 13 Ambient Temperature Sensor GS Gas Detection Element TC Compensation Element

Claims (9)

[Claims] 1. A gas leak such as city gas or propane gas,
A gas leak alarm device that detects CO gas generated due to incomplete combustion and issues an alarm when the gas concentration rises above a predetermined level. A gas sensor that outputs a signal in response to gas, and an alarm Unit, a control means having a non-volatile memory, and a power supply circuit are combined, and the gas concentration level for issuing an alarm is stored in the memory as an operation set value, and the set value and the sensor output are compared and controlled. A gas leak alarm, wherein the means determines whether or not an alarm operation is required. 2. The gas leakage alarm device according to claim 1,
A gas leak alarm, wherein the integrated control means is a microcomputer. 3. The gas leak alarm according to claim 2,
Characterized by reading the sensor signal output at the reference gas concentration in the process of executing the program of the microcomputer, storing it in the memory, setting the alarm operation level based on the memory value, and determining the necessity of the alarm operation. Gas leak alarm device. 4. The gas leak alarm device according to claim 1, wherein the communication means has a function of setting operation mode with an external device, receiving alarm operation determination data, and output device designation data. Gas leak alarm device characterized by having. 5. The gas leakage alarm device according to claim 4,
A gas leak alarm device having a function of transmitting an operation status of gas detection with an external device through a communication means. 6. The gas leak alarm device according to claim 4,
A gas leak alarm device having a function of constantly transmitting a signal level of a gas sensor between external devices via a communication means. 7. The gas leak alarm device according to claim 1, further comprising an ambient temperature sensor for detecting an ambient temperature of the gas sensor, and the sensor output is programmatically based on the temperature signal of the sensor based on the temperature signal of the ambient temperature sensor. A gas leak alarm that has the function of correcting 8. The gas leak alarm according to claim 1, wherein the gas leak alarm has a function of determining the zero drift output level of the sensor and correcting the drift of the sensor signal. 9. A gas leak alarm which has the function according to any one of claims 1 to 8 and detects the gas concentration of an incomplete combustion gas contained in the exhaust gas of a gas appliance.