JPH073398B2 - Gas detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a gas detection device capable of performing a sensitivity inspection operation by one worker.

[Conventional technology]

The stationary industrial gas detector is generally composed of a gas detector, a gas concentration indicator and an alarm device. That is,
As shown in FIG. 3, the gas sensors S ₁ , S ₂ , and S ₃ are several meters to several meters.
It is connected to the gas concentration indicators U ₁ , U ₂ and U ₃ via the Km gas detector cables C ₁ , C ₂ and C ₃ . The AU is an alarm device, which is equipped with a buzzer and the like, and issues an alarm when an instruction of a gas concentration indicator U _{1 to} U ₃ of a level higher than a predetermined level is given. PW is the power supply section, A,
B, P and R are lines, A is an alarm circuit line, B is a buzzer signal circuit line, R is an alarm stop circuit line, P is a power supply circuit line, and ALD is a gas detector main body.

The gas concentration indicators U _{1 to} U ₃ and the alarm device AU are installed in non-hazardous areas such as offices and control rooms due to explosion-proof, and the gas sensors S _{1 to} S ₃ are installed in hazardous areas where gas leakage may occur. . Gas sensor
Generally, sensitivity and zero base of S _{1 to} S ₃ are subject to environmental conditions and change with time, and therefore it is necessary to regularly check and adjust the sensitivity.

[Problems to be solved by the invention]

In the above conventional gas detection device, the sensitivity inspection and adjustment work is performed by gas sensors S _{1 to} S ₃ , gas concentration indicators U _{1 to} U ₃ and an alarm device AU.
Since it is installed separately, it is necessary to apply the standard gas to the gas sensors S _{1 to} S ₃ and check and adjust the indicated values of the gas concentration indicators U _{1 to} U ₃ and the alarm AU at the same time. Therefore, the sensitivity inspection work always required two or more workers.

As another conventional technology, a method is available in which standard gas is installed in the field, the solenoid valve is operated by the button operation on the indicator / alarm unit side, the test gas and the standard gas are switched, and the instruction is automatically calibrated. However, this has a problem that the price becomes very expensive. Further, this method has a drawback that the gas sensor can be applied to the automatic suction type, but cannot be applied to the natural permeation type.

It is an object of the present invention to provide a gas detection device having a maintenance function that allows one person to perform an inspection and adjustment work that has always required two or more workers.

[Means for solving problems]

In the gas detection device according to the present invention, the indicator unit is provided with a maintenance switch, and the indicator unit is provided with a first timer and a warning buzzer which are in a maintenance mode when the maintenance switch is ON for a certain time or more. A second timer for automatically stopping after sounding for a time and a peak hold circuit for holding the maximum value of the gas concentration detected by the gas sensor are provided.

[Action]

According to the present invention, when the maintenance switch is turned on and the first timer is set to the maintenance mode, and the standard gas is blown to the gas sensor installed at a remote place,
The maximum value of the gas concentration is held in the gas concentration indicator.
Therefore, the instruction of the gas concentration indicator can be calibrated by returning to the main body of the gas detection device. At this time, the buzzer sounds, but the second timer automatically stops after a certain time.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. In this figure, 10 is an indicator unit and 20 is an alarm unit. In the indicator unit 10, S is a gas sensor, PA is a preamplifier, PH is a peak hold circuit, MA is a main amplifier, VR ₁ is a variable resistor for span adjustment used for calibration of instructions, and M is a gas concentration indicator. is there. COM is a comparator, which is turned on when the indication of the gas concentration indicator M exceeds a certain level, and the self-holding circuit SH holds the alarm state. BC is a buzzer signal circuit, which is turned on when the comparator COM is turned on and is kept on until the alarm stop button is pressed in the alarm unit 20. T ₁ is a first timer that determines the inspection start time, T ₂ is a _second timer that determines the buzzer sounding period, RY ₁ is a relay,
Switches each contact RY _1a , RY _1b , RY _1c . Alarm unit
In FIG. 20, BI is a buzzer intermittent circuit, BZ is a buzzer, RY ₂ is a relay, L is a lamp, SW _r is an alarm stop switch, and SW _m is a maintenance switch. R is an alarm stop circuit line. Usually, since the maintenance switch SW _m is used in the OFF state, the alarm signal representative lamp A line, a buzzer signal is transmitted to the B line.

When the alarm stop switch SW _r is pressed, the buzzer signal circuit BC
It is configured to be FF. The line A continues to be in the ON state in which the lamp alarm signal is applied from the self-holding circuit SH if the comparator COM is still in the ON state, and is turned off if the comparator COM is turned off. It is customary to press the alarm stop switch SW _r for about 1 second, and even if the buzzer BZ stops, it does not continue to press, so the first timer T ₁ does not operate.

If the maintenance switch SW _m is turned on, and the timer T ₁ is set to, for example, 10 seconds, it is turned on after 10 seconds and the relay RY ₁ is activated. Therefore, the contact RY _1a is switched, and the connection from the preamplifier PA to the main amplifier MA is directly connected via the peak hold circuit PH, and the maximum value of the output of the gas sensor S is held. The gas concentration indicator M also indicates the maximum value. In the self-holding circuit SH, contact RY _1b is OF
Since it becomes F, the R line (reset line) maintains the alarm state even if it is in the ON state.

The contact point RY _{1c of the} buzzer signal circuit BC is switched, and the buzzer signal circuit BC is connected to the line B via the second timer T ₂ . Second timer T ₂
For example, if you set it to 5 seconds, the buzzer will sound for 5 seconds and then stop.

By doing so, even if no one is on the alarm device body, waiting for an instruction from the gas sensor S can be maintained simply by turning on the maintenance switch SW _m , so that the alarm device body can be installed far away from the alarm device body. The standard gas whose concentration is known to the gas sensor S is passed around for several minutes, for example, for one minute per one time (time until the output of the gas sensor S is sufficiently stable), and then returned to the main body of the gas detection device to indicate the indicator. It is possible to calibrate the gas concentration indicator M with the variable resistor VR ₁ sequentially while checking the indicated value of the unit 10.

The maintenance switch SW _m may not be provided on the line R which is the alarm stop circuit, but a dedicated maintenance line may be provided and the maintenance switch SW _m may be provided there. In this case, the first timer T ₁ is unnecessary, but the number of wires between units increases by one. Connection between units is usually done by connector wiring in many cases, and the number of connector poles is often limited. However, since the present invention can share the line R, the number of connector poles can be used as it is and is compatible with the old model. There are great advantages such as maintaining sex.

The above-mentioned embodiment is a case where only the analog circuit is used, but the first and second timers T ₁ and T ₂ , the comparator COM, the self-holding circuit SH, and the peak in the indicator unit 10 in FIG. If the hold circuit PH or the like uses a microcomputer and the gas concentration indicator M is replaced with a digital type or bar graph meter or the like, a maintenance function can be added more easily.

Such an embodiment is shown in FIG.

In Figure 2, MD is a digital gas concentration indicator, MP
Multiplexer, 1NV ₁ ~1NUV ₃ an inverter, CPU microcomputer, VR ₂ is a variable resistor for Alam set, others are the same as the embodiment of Figure 1.

〔The invention's effect〕

As described above, according to the present invention, the indicator unit is provided with a maintenance switch, and the indicator unit is put into the maintenance mode when the maintenance switch is turned on for a predetermined time or more, and the alarm buzzer is operated for a predetermined time. Since a second timer for automatically stopping after ringing and a peak hold circuit for holding the maximum value of the gas concentration detected by the gas sensor are provided, when a gas having a standard concentration is blown to the gas sensor at a remote location,
Since the maximum value is held in the gas concentration indicator, it is possible to return to the main body of the gas detection device for calibration. Therefore, one worker can calibrate without requiring two or more workers as in the conventional case. Furthermore, when the maintenance switch is operated, the automatic maintenance mode is set by the first timer, so there is no need to wastefully wait for the gas sensor installed at a remote place. Further, the buzzer sounds when the gas of the standard concentration is sprayed on the gas sensor, but since it stops after a certain time by the second timer, there is an excellent effect such that no noise occurs.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing another embodiment of the present invention, and FIG. 3 is a circuit diagram showing an example of a conventional gas detection alarm device. In the figure, 10 is an indicator unit, 20 is an alarm unit, S is a gas sensor, PA is a preamplifier, MA is a main amplifier, PH is a peak hold circuit, VR ₁ is a variable resistor for span adjustment, and M is gas concentration. Indicator, COM is a comparator, SH is a self-holding circuit, BC is a buzzer signal circuit, T ₁ and T ₂ are first and second timers,
BI is a buzzer intermittent circuit, BZ is a buzzer, SW _r is an alarm stop switch, and SW _m is a maintenance switch.

Claims (1)

[Claims] 1. One or more indicator units each having a gas sensor installed at a remote place for detecting a gas leak, a gas concentration indicator for indicating the output of the gas sensor, and a variable resistor for span adjustment are connected. Along with an alarm buzzer,
In a gas detection device having an alarm unit equipped with an alarm stop switch for stopping the operation of this alarm buzzer, a maintenance switch is provided in the indicator unit, and the maintenance switch is turned on in the indicator unit for a certain time or more. When the maintenance timer is set to a maintenance mode, a first timer, a second timer that automatically stops after the alarm buzzer sounds for a certain period of time, and a peak hold circuit that holds the maximum value of the gas concentration detected by the gas sensor are provided. A gas detection device characterized by being provided.