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7-3. Trouble Alarm Operation
This unit can detect an internal failure. When an internal failure is detected, a trouble alarm will activate (open
collector is normally ON (closed position) and in the event of a trouble alarm it switches to OFF (open
position)). The amber TROUBLE LED will start flashing, and the analog output will fall to 0.6 mA or less.
Self-resetting: When a problem is removed, the TROUBLE LED, open collector, and analog output will
automatically return to their normal positions/status.
Please
refer to 10. ―Troubleshooting.‖
The internal failures include the following:
(1) Low flow rate
When a minimum flow rate is not present, the unit determines the flow rate to be too low. FLOW is
shown on the LCD and the spinning flow-rate icon stops. The low flow rate is caused by: a clogged filter
element, clogged tubing, excessive negative pressure, worn pump, etc.
(2) Sensor fault
SENS. appears on the LCD in the following situations:
- When the
sensor’s zero-level output is extremely low.
- When a broken sensor wire is detected. This applies to a combustible gas sensor (CHS-7) only.
(3) Incorrect sensor installed
The data (e.g., target gas type, full scale value) from the last installed sensor is recorded by the gas
detector. If a newly installed sensor unit does not match, the gas detector will detect that an incorrect
sensor unit has been installed, and display SENS. And
― - - - -‖ on its LCD. To use a newly installed
sensor unit that does not match the previous sensor type, press the COMM. button to renew the data.
(4) Broken pyrolyzer wire (when the detector uses a pyrolyzer)
If a broken wire is detected, CONV. will appear on the LCD.
(5) No power
If the gas detector is not powered, all the LEDs will turn off and the detector will stop operation.
(6) Blown fuse
If the fuse is blown due to which the unit loses power, then all the LEDs will turn off and the detector will
stop operation.
(7) Memory read error
When the internal memory cannot be normally read after power-up
, ―nG‖ will be displayed on the LCD.