JPS63285455A - Gas detector - Google Patents

Abstract

PURPOSE:To reduce the number of workers for calibration to one, by a method wherein a gas concn. indicator is provided with a means to maintain the max. value of the concn. of a gas, then, a worker blows a reference density of gas to a gas sensor at a remote point and returns to a main unit. CONSTITUTION:When a maintenance switch SWm is turned ON, a timer T1 is switched ON after a set time and a relay RY1 starts to work, which causes a contact RY1a to be switched over to a main amplifier MA through a peak holding circuit pH from a preamplifier PA to maintain the max. value of an output of a gas sensor S. A self-holding circuit SH is kept ready for alarming even when a line R is ON as a contact RY1b is turned OFF. With such an arrangement, a worker moves to apply a reference gas all the way to a gas sensor S located away from an alarm body and, then, returns to the main unit side of a gas detector to check an indication of an indicator unit 10. Afterward, the calibration of a gas concn. indicator M is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a gas detection device in which sensitivity inspection work can be performed by one worker.

(Prior Art) Industrial stationary gas detection devices generally include a gas detection section, a gas concentration indicator, and an alarm. That is,
As shown in FIG. 3, the gas sensor S In22. S s
Cales C1, C2, C3 for gas detection parts whose distance is several meters to several kilometers
A gas concentration indicator U1. Connected to U2゜U3. AU is an alarm, equipped with a buzzer, etc., and a gas concentration indicator U.
, ~U3, an alarm is issued when an instruction of a level higher than the specified level is given. PW is the power supply section, A, B, P, R are lines, A is the alarm circuit line, B is the buzzer signal circuit line,
R is alarm stop circuit line, P is power supply circuit line, A
LD is the main body of the gas detection device.

Gas concentration indicators U1 to U3 alarms AU are installed in explosion-proof non-hazardous locations such as offices and control rooms, and gas sensors 31 to
S is installed in a hazardous location where there is a risk of gas leakage. The sensitivity and zero base of the gas sensors 31 to S3 generally change due to environmental conditions and oral changes, so the sensitivity needs to be regularly inspected and adjusted.

(Problems to be Solved by the Invention) In the conventional gas detection device described above, the sensitivity inspection and adjustment work is equivalent to applying standard gas to the gas sensor because the gas sensor, gas concentration indicator, and alarm are installed separately. It was necessary to check and adjust the indicated values of the gas concentration indicator and alarm at the same time, and the sensitivity inspection work always required a worker with a height of 2 Å or more.

Another conventional technology is to install standard gas at the site and operate a solenoid valve by pressing a button on the indicator/alarm unit.
A method has been put into practical use that automatically calibrates the instructions by switching between the test gas and the standard gas, but this method has the problem of being extremely expensive. Furthermore, this method has the disadvantage that it can be applied to automatic suction type gas sensors, but cannot be applied to natural permeation type gas sensors.

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas detection device having a maintenance function that allows a single person to perform inspection and adjustment work that conventionally required an operator of 2 Å or more.

[Means for solving problems]

The gas detection device according to the present invention includes a gas concentration indicator equipped with means for holding the maximum value of the gas concentration detected by the gas sensor.

[Effect]

In this invention, when a standard gas is sprayed onto a gas sensor installed at a remote location, the maximum value of the gas concentration is held in the gas concentration indicator. Therefore, the indication of the gas concentration indicator can be calibrated by returning to the main body of the gas detection device.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention. In this figure, 10 indicates an indicator unit, and 20 indicates an alarm unit. In the indicator unit 1o, S is a gas sensor, PA is a preamplifier, PH is a peak hold circuit, MA is a main amplifier, VR is a variable resistor for span adjustment used for calibrating the indication, and M is a gas concentration indicator. . C.O.
M is a comparator which is turned ON when the indication from the gas concentration indicator M exceeds a certain level, and the alarm state is maintained by a self-holding circuit SH. BC is a buzzer signal circuit that is turned ON when the comparator COM is turned ON, and remains ON until the alarm stop button is pressed in the alarm unit 20. T1 is a timer that determines the inspection start time, T2 is a timer that determines the buzzer ringing period, RY1 is a relay, and each contact RYIa + R" It
l* RY I (j is switched. Alarm unit 2o
In, BI is a buzzer intermittent circuit, BZ is a buzzer, RY
2 is a relay, L is a lamp, SWr is an alarm stop switch,
SWo is a maintenance switch. Since the maintenance 5WIIl is normally used in the OFF state, an alarm signal for the representative lamp is sent to the A line, and a buzzer signal is sent to the B line.

When alarm stop switch SW is pressed, buzzer signal circuit B
C is configured to be OFF. If the comparator COM remains in the ON state, the line A will continue to be in the ON state where the lamp alarm signal is applied from the self-holding circuit SH, and if the comparator COM becomes OFF, it will turn OFF.
It becomes F.

It is customary to press the alarm stop switch SWr for about 1 second, but do not keep pressing it even after the buzzer BZ has stopped.
Timer T1 does not operate.

Maintenance SWI! When l is turned ON, timer TI is
For example, if it is set to 10 seconds, the O
becomes N, and relay RYI works. Therefore, the contact RY1. The connection from the preamplifier PA to the main amplifier MA is changed from direct connection to 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 its maximum value. Since the contacts RY and b of the self-holding circuit SH are OFF, the R line (
The reset line) maintains the alarm state even if it is in the ON state.

The buzzer signal circuit BC is connected to the line B via the timer T2 by switching the contacts RY and c.

If the timer T2 is set to 5 seconds, for example, the buzzer will sound for 5 seconds and then stop.

By doing this, even if no one is present at the main body of the alarm system, simply turning on the maintenance 5WIa will keep the gas sensor waiting for instructions, so the gas sensor S installed far away from the main body of the alarm system can be Apply a standard gas of known concentration to several locations, for example, for 1 minute at each location (the time it takes for the output of the gas sensor to become sufficiently stable), then return to the main body of the gas detection device and check the indicator unit 10. Adjust the variable resistor V sequentially while checking the indicated value.
At R, the gas concentration indicator M can be calibrated.

The maintenance SW is not installed in line R, which is the alarm stop circuit, but a dedicated maintenance line is installed c-+
A maintenance SW may also be provided there. In this case, timer T is not required, but the number of wires between units increases by one. Connections between units are usually made using connector wiring, but there is often a limit to the number of connector pins; however, with this invention, line R can be shared, so the number of connector pins can remain the same, making it compatible with older models. It has many advantages, such as being able to maintain

Although the above embodiment is composed of only analog circuits, the timer T in the indicator unit 10 in FIG.
,,T2. Comparator COM, self-holding circuit SH,
If a microcomputer is used for the peak hold circuit PH, etc., and the gas concentration indicator M is replaced with a digital type or a bar grapher, 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 is a multi-channel I/XA, INV, -INU3 is an inverter, CPU is a microcomputer, VR2 is a variable resistor for an ARAM set, and the other components are the same as in the embodiment shown in FIG.

(Effects of the Invention) As described above, the present invention is equipped with a means for holding the maximum value of the gas concentration detected by the gas sensor in the gas concentration meter, so that when a gas at a standard concentration is sprayed onto a gas sensor located 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 and perform calibration.

Therefore, there is an excellent effect that the calibration can be carried out by one worker without requiring a worker of 2 Å or more as in the conventional case.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a circuit diagram showing another embodiment of the 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 the gas sensor, PA is the preamplifier, MA is the main amplifier, P
H is a peak hold circuit, VR. is a variable resistor, M is a gas concentration indicator, COM is a comparator, SH is a self-holding circuit, BC is a buzzer signal circuit, T
,, T2 is a timer, B1 is a buzzer intermittent circuit, BZ is a buzzer, SWr is an alarm stop switch, and SWl, l is a maintenance switch. Figure 2 Figure 3

Claims (1)

[Claims] In a gas detection device having a gas sensor installed at a remote location to detect gas leaks and a gas concentration indicator that indicates the output of the gas sensor, the gas concentration indicator holds a maximum value of the gas concentration detected by the gas sensor. A gas detection device characterized by comprising means.