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7.3 Operation mode
7.3.1 Sensor stabilization time (WARMM-UP)
You have to wait for sensor stabilization time because a detector does not act immediately.
At this time, the value from 0 to 100 %LEL are indicated for 30 second. (Sensor stabilization time)
1) Alarm output does not brake out. (Alarm output stop for a while)
2) Transmitter output is 3 mA.
7.3.2 Normal action
1) Sensor stabilization time is end, then instrument act for operation mode. At the operation mode,
the measuring value is indicated as a cumulative form on the bar graph.
2) When the measuring value excess the alarm setting point, then instrument output an alarm
contact and LED flicker.
3) In case of common unit make an alarm return signal after alarm is acted.
⊙
In case of alarm state is held (the measuring value excess the alarm set point) LED for alarm
state is changed from flickering to on state.
⊙
In case of alarm state is canceled (the measuring value fall below the alarm set point) LED for
alarm state is changed from flickering to on state and contact output is off.
4) An instrument generates transmitter output of measuring value with the range 4-20 mA.
For initial stabilization time, a detector makes 2 mA transmitter output.
When a fail signal is generated, a detector makes 2 mA transmitter output.
When a transmitter input is below 2 mA, a detector makes fail signal.
7.3.3 Calibration method
I. Diffusion combustible gas detector (Non-Transmitter)
1) You may confirm the sensor current of connected detector. (Refer to Fig. 7.1)
2) HEATING CURRENT SETTING: You calibrate the corresponded current by HEATING CURRENT
VR. At this time, you can confirm the value by a voltmeter. You may set the unit of voltmeter to volt
and you connect the probe of voltmeter to current check pin. The unit is volt but you have to read
for current because one ohm resistor is inserted.
(example; 295 mV × 1Ω = 295 mA)
.
3) ZERO SETTING : After calibrate heating current, you have to wait for ten hours, and then you
calibrate the zero point. You may set zero by ZERO VR.
4) SPAN SETTING : You inject a standard gas (assume 50 %LEL) to a sensor.
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