JP2012164094A - Gas alarm and heater voltage setting method of gas sensor in gas alarm - Google Patents

Abstract

The present invention relates to a sensor voltage adjustment technique in a gas alarm device, and reduces the man-hour for initial setting of a heater voltage.
The following control is executed at the time of initial setting of a gas alarm. First, the control circuit unit 104 applies a heater voltage to the heater resistor 103 in the gas sensor 101 via the constant voltage circuit unit 110. The control circuit unit 104 calculates the voltage value and the current value at both ends of the heater resistor via the AD conversion input terminals AD1 and AD2, and calculates the heater power as the product of them. The control circuit unit 104 controls the heater voltage so that the heater power becomes a predetermined set value.
[Selection] Figure 1

Description

  The present invention relates to a technology for adjusting a heater voltage of a gas sensor in a gas alarm device.

  In the gas alarm device, a gas sensor is used to detect a detection target gas such as city gas or LP gas. The gas sensor is used by applying a voltage to the heater resistance and heating the heater temperature to a predetermined temperature such as 400 ° C. in order to detect gas. And gas detection is performed by measuring the change of the sensor resistance which changes with reaction with detection gas.

  The heater temperature can be controlled by the amount of electric power (voltage × current) injected into the heater section. When the heater temperature is lower than a predetermined value, the sensitivity of the sensor with respect to the detection gas is insufficient, or the sensitivity is increased with respect to gases other than the detection gas. If the heater temperature is higher than a predetermined value, the sensor itself may be damaged in addition to a change in sensitivity to gas. Therefore, it is necessary to keep the heater temperature constant.

  In addition, although the heater is manufactured from a metal-based material, it is difficult to produce a constant heater resistance value due to manufacturing variations, etc., and even if the same heater voltage is applied to all sensors, Since the flowing current is not constant, there is a problem that the heater temperature is not constant.

  For this reason, conventionally, in order to correct the heater temperature variation caused by variations in the heater resistance value of each sensor and to keep the heater temperature constant, the heater voltage of each gas sensor is adjusted and stored in the main body of the alarm device. It was necessary to let them.

FIG. 3 is a flowchart showing a heater voltage control process in the prior art.
First, it is determined whether the mode is the normal use mode or the mode for adjusting the heater (S1 in FIG. 3). The gas alarm device has a mode for performing various settings of the alarm device in addition to a mode for detecting a normal gas leak.

In the heater adjustment mode (when the determination of S1 in FIG. 3 is Yes), the heater voltage applied to the heater part of the gas sensor can be set from the outside.
First, a heater circuit voltage setting value that makes the target heater temperature reach the control circuit unit (microcomputer) from the adjustment signal setting unit connected to the outside of the gas alarm device via the adjustment signal input unit inside the gas alarm device (S2 in FIG. 3).

The control circuit unit applies the heater voltage to the gas sensor based on the set heater voltage setting value (S3 in FIG. 3).
The heater voltage at this time is measured (S4 in FIG. 3), and it is determined whether or not the measured heater voltage is the same as the heater voltage setting value (S5 in FIG. 3).

  If the determination result is inconsistent, the process returns to S2 in FIG. 3 to change the heater voltage and set the heater voltage setting value again, and the processes from S2 to S5 in FIG. 3 are measured in S5 in FIG. The process is repeated until the heater voltage matches the heater voltage setting value.

  When it is determined that the heater voltage measured in S5 of FIG. 3 matches the heater voltage setting value (Yes in S5), the heater voltage setting value at that time is written to the EEPROM, and the heater voltage control process is terminated. (S6 in FIG. 3).

JP 1999-248661 A

  However, in the control method shown in FIG. 3, the measurement of the heater voltage in S <b> 4 in FIG. 3 and the coincidence determination between the measured heater voltage and the heater voltage set value in S <b> 5 are conventionally performed by a manufacturer using a measuring instrument. I confirmed one unit. For this reason, there has been a problem that the number of man-hours for the initial setting of each unit increases.

Further, since the manufacturer manually performs delicate power adjustment according to the variation in the resistance value of the heater unit, there is a concern that not only the adjustment cost increases but also an adjustment error occurs.
Accordingly, an object of the present invention is to reduce the man-hours for initial setting of the heater voltage so that a reliable adjustment can be performed without any error during adjustment.

In an example, the embodiment is realized as a gas alarm including a gas sensor that needs to keep the heater temperature constant, and has the following configuration.
The heater voltage application unit applies a heater voltage to the heater resistance in the gas sensor.

The heater power calculation unit calculates the heater power by calculating the voltage value and the current value across the heater resistance.
The heater voltage variable unit controls the heater voltage so that the heater power becomes a predetermined set value at the time of initial setting.

  By applying the calculated heater voltage to the heater resistance from the heater voltage application unit, it is possible to achieve control to keep the heater temperature constant, and to improve the accuracy of detection of gas leakage.

It is no longer necessary to manually adjust the heater voltage for each gas alarm device, and the initial setting man-hours can be reduced.
In addition, there is no manual adjustment error, and reliable adjustment can be performed.

It is a block diagram of embodiment of the gas alarm device by this invention. It is a flowchart of the heater voltage adjustment process by embodiment. It is a flowchart of the heater voltage adjustment process by a prior art.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram of an embodiment of a gas alarm device according to the present invention.
The gas sensor 101 includes a sensor resistor 102 for detecting gas and a heater resistor 103 for heating the sensor.

  The battery unit 105 supplies 3 volt power. The booster circuit unit 106 sets the voltage of 3 volts from the battery unit 105 to a predetermined constant voltage, and supplies the constant voltage to the sensor system circuit including the sensor resistor 102, the load resistor 107, and the SW2 108 in the gas sensor 101. . Further, a constant voltage is supplied to a heater system circuit including SW1 109, a constant voltage circuit unit 110, a heater resistor 103, and a shunt resistor 111. Further, a constant voltage is supplied to the power supply terminal VDD of the control circuit unit 104.

  The control circuit unit 104 is a microcomputer that controls the operation of the entire gas alarm device. The control circuit unit 104 turns on SW1 109 and SW2 108 that are transistor switches via the output terminals OUT1 and OUT3. As a result, the sensor resistor 102 in the gas sensor 101, the load resistor 107, and the sensor system circuit composed of SW2 108, the SW1 109, the constant voltage circuit unit 110, the heater resistor 103, and the heater composed of the shunt resistor 111. The system circuit is operated. Further, the control circuit unit 104 determines a gas leak by detecting a sensor output voltage of the gas sensor 101 via an AD (analog-digital) conversion input terminal AD3. Further, the control circuit unit 104 supplies the heater voltage value to the constant voltage circuit unit 110 via the output terminal OUT2. OUT2 is a DA (digital-analog) output or a PWM (pulse width modulation) output, and supplies a predetermined voltage to the constant voltage circuit unit 110. In addition, the control circuit unit 104 automatically measures the heater power based on the control output from the AD conversion input terminals AD1 and AD2 at the initial setting of the gas alarm device, and the measured heater power is a predetermined heater power set value. The heater voltage supplied to the constant voltage circuit unit 110 is gradually varied so as to match the above. The heater power setting value described above is a value described in the microcomputer software of the control circuit unit 104 or a value set from the adjustment signal setting unit 118 via the adjustment signal input unit 116 and the input terminal IN1.

  Although the detailed description is omitted in this embodiment, the ambient temperature detection unit 117 inputs an ambient temperature value to the control circuit unit 104 via the AD conversion input terminal AD4, and the heater voltage based on the ambient temperature is input to the control circuit unit 104. To implement the control.

  The alarm unit 112 includes an alarm sound output unit 113, an alarm display unit 114, and an external alarm output unit 115. The alarm sound output unit 113 is a part that emits a sound such as an alarm sound, and is configured by, for example, a buzzer or a speaker. Based on the control from the control circuit unit 104, the alarm sound output unit 113 notifies the gas leak state by an electronic sound or a voice message. The alarm display unit 114 is configured by an LED (light emitting diode), and informs the state of the alarm device by the LED such as lighting the LED at the time of monitoring and blinking the LED at the time of alarm. The external alarm output unit 115 outputs an alarm signal to an external device such as a gas meter or a centralized monitoring panel.

  In the above-described configuration, a portion including the control circuit unit 104 and the constant voltage circuit unit 110 forms a heater voltage application unit, and a portion including the shunt resistor 111 and the control circuit unit 104 forms a heater power calculation unit. Unit 104 further constitutes a heater voltage variable unit.

  In the present embodiment, the gas sensor 101 is driven every sensor driving time of about 100 ms (milliseconds) in a sensor driving cycle of 20 to 60 seconds. Specifically, the control circuit unit 104 shown in FIG. 1 executes the following operation every time an interruption occurs every sensor driving time in the sensor driving period based on control by a timer (not shown). That is, the control circuit unit 104 first turns on SW1 109 to operate a heater system circuit including SW1 109, constant voltage circuit unit 110, heater resistor 103 in the gas sensor 101, and shunt resistor 111. . At this time, the heater voltage setting value calculated at the time of initial setting described later and held in the EEPROM is applied to the constant voltage circuit unit 110. Thereby, the gas sensor 101 is heated within the sensor driving time. Subsequently, the control circuit unit 104 operates a sensor system circuit including the sensor resistor 102, the load resistor 107, and the SW2 108 in the gas sensor 101 by turning on the SW2 108. Thereby, the control circuit unit 104 performs the gas leak detection operation within the sensor driving time.

  FIG. 2 is a flowchart of the heater voltage adjustment process according to the embodiment. Here, the process of the flowchart which shows the whole process for adjusting a heater drive voltage of Fig.2 (a) is performed by the control circuit part 104 at the time of the initialization of a gas alarm device.

  First, it is determined whether the mode is the normal use mode or the mode for adjusting the heater (S1 in FIG. 2A). The gas alarm device of the present embodiment includes a mode for performing various settings of the alarm device in addition to the normal mode, as in the conventional technology. When the gas alarm device is initially set, the heater adjustment mode is first set.

If the result of the determination in S1 is not the heater adjustment mode (when the determination in S1 in FIG. 2A is No), the heater adjustment process is not executed.
When the heater adjustment mode is set at the initial setting of the gas alarm (when the determination of S1 in FIG. 2A is Yes), a heater adjustment command is further input from the outside of the control circuit unit 104 in FIG. It will be in a standby state until it is performed (determination of S2 of Fig.2 (a) is No repetition).

  When the heater adjustment command is input (Yes in S2 in FIG. 2A), the control circuit unit 104 starts the heater voltage automatic setting process (S3 in FIG. 2A). FIG. 2B is a flowchart showing details of the process of S3.

  First, in FIG. 1, the control circuit unit 104 supplies a heater voltage value to the constant voltage circuit unit 110 via the output terminal OUT2. As a result, the constant voltage circuit unit 110 applies a heater voltage corresponding to the heater voltage value supplied from the control circuit unit 104 to the heater resistor 103 in the gas sensor 101 (S1 in FIG. 2B). In this case, the heater voltage applied first is controlled to be a little lower than the voltage at which the gas sensor 101 should operate normally. Then, when S1 of FIG. 2B is executed after the second time, the heater voltage value supplied to the constant voltage circuit unit 110 is adjusted so that the voltage gradually increases.

  Next, the control circuit unit 104 reads the heater voltage value applied to both ends of the heater resistor 103 of the gas sensor 101. Specifically, a value obtained by subtracting a value input to the AD conversion input terminal AD2 from a value input to the AD conversion input terminal AD1 is the calculated heater voltage value (FIG. 2B). S2).

  Subsequently, the control circuit unit 104 reads the voltage value of the shunt resistor 111 from the AD conversion input terminal AD2, converts the voltage value, and calculates a current value (S3 in FIG. 2B). In practice, the voltage across the shunt resistor 111 is amplified by an operational amplifier and measured. The current detection by the shunt resistor is also used for the purpose of, for example, detecting a current to detect an abnormality of the heater resistor 103 in the gas sensor 101 and issuing a failure alarm.

  Further, the control circuit unit 104 calculates heater power by calculating the product of the heater voltage value calculated in S2 of FIG. 2B and the current value calculated in S3 of FIG. S4 in FIG.

  Then, the control circuit unit 104 determines whether or not the heater power calculated in S4 of FIG. 2B is a predetermined power value (for example, 30 mW (milliwatt)) (S5 of FIG. 2B). . The predetermined power value is held in the memory in the control circuit unit 104 from the adjustment signal setting unit 118 of FIG. 1 via the adjustment signal input unit 116 and the input terminal IN1.

  As a result of the determination, if the heater power does not match the predetermined power value (No in S5 in FIG. 2B), the heater voltage value supplied to the constant voltage circuit unit 110 via the output terminal OUT2 is slightly It is made higher and the process from S1 in FIG.

The series of processes from S1 to S5 in FIG. 2B is repeatedly executed until the heater power matches the predetermined power value.
When the heater power matches the predetermined power value (Yes in S5 in FIG. 2B), the heater voltage automatic setting process in S3 in FIG. 2A is terminated, and the heater voltage automatically set in S3 is determined. The set value is stored in a memory in the control circuit unit 104 or an external EEPROM (S4 in FIG. 2A). Thereby, the control circuit unit 104 ends the control process shown in the flowchart of FIG.

  As described above, in the present embodiment, the heater voltage setting value is automatically adjusted by simply executing the heater adjustment command at the initial setting of the gas alarm device. As a result, it is not necessary to manually adjust the heater voltage for each unit, and the number of initial settings can be reduced.

DESCRIPTION OF SYMBOLS 101 Gas sensor 102 Sensor resistance 103 Heater resistance 104 Control circuit part 105 Battery part 106 Boosting circuit part 107 Load resistance 108 SW2
109 SW1
110 Constant Voltage Circuit Unit 111 Shunt Resistance 112 Alarm Unit 113 Alarm Sound Output Unit 114 Alarm Display Unit 115 External Alarm Output Unit 116 Adjustment Signal Input Unit 117 Ambient Temperature Detection Unit 118 Adjustment Signal Setter

Claims (4)

In a gas alarm equipped with a gas sensor that needs to keep the heater temperature constant,
A heater voltage application unit for applying a heater voltage to the heater resistance in the gas sensor;
A heater power calculator that calculates a heater power by calculating a voltage value and a current value across the heater resistance; and
A heater voltage variable unit for controlling the heater voltage so that the heater power becomes a predetermined set value at the time of initial setting;
A gas alarm device comprising: The heater voltage application unit includes a constant voltage circuit unit.
The gas alarm device according to claim 1. The heater power calculation unit detects a voltage value and a current value at both ends of the heater resistor via a shunt resistor connected to the heater resistor, and calculates the heater power as a product of the voltage value and the current value.
The gas alarm device according to claim 1. At the initial setting of a gas alarm equipped with a gas sensor that needs to keep the heater temperature constant,
Applying a heater voltage to the heater resistance in the gas sensor;
Calculate the heater power by calculating the voltage value and current value across the heater resistance,
Controlling the heater voltage so that the heater power becomes a predetermined set value;
A heater voltage setting method for a gas sensor in a gas alarm device.

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