TQ Environmental LTD
Product Manual TQ 4000
Filename: 7970H8 Page 23 of 27
7. Fault Finding
7.1. Unit does not power up
Check mains input, fuse on power supply
7.2. Flammable gas sensors will not go to zero on setup
Usual problem is that the flammable gas card has not been set up in
accordance with procedure. Check in particular the sensor zero is at
1.00mV positive.
If the flammable gas card is set up correctly remove sensor and insert
dummy load resistors 3R3 1% to simulate sensor and adjust zero. If display
now moves towards zero when down is pressed the sensor or sensor wiring
is suspect.
Another problem may be damaged up and down push buttons, physically
check the push button.
7.3. Flammable gas sensor when gassed do not span high enough
Most likely problem is that the sensor head voltage is below the required
2 volts. Measure the voltage at the sensor head, not the input terminal on
the PCB. Bring voltage up to 2.00V and recalibrate.
Check that gas can is not empty and that there is an airtight seal around
the gassing cup. For TQ flammable sensors use TQ gassing cup.
7.4. Flammable gas sensor moves erratically when gassed
Check the control electronics by evoking test mode and allowing unit to
cycle through. If the display is still erratic as opposed to a steady sweep,
electronics are suspect.
Check that gassing is being done at a rate of not greater than 0.5litre/min
and that a gassing cup is used.
7.5. Display is cycling from 0 to end of scale and alarms are sounding
The unit is in system test mode. Exit system test by following procedure
described in point 6 above.
7.6. Relays fail to activate on alarm
Check that channel is not inhibited if it is release by pressing down key.
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