Detcon FP-624D - Manual (Page 16)

Model FP-624D
FP-624D Instruction Manual Rev. 1.2 Page 12 of 42
This adjustment is only required after initial installation and will not be necessary thereafter, except in the
event of replacement of the plug-in sensor. Refer to section 3.5.5 to perform this adjustment.
NOTE: Refer to section 3.5.5 to set the sensor bridge voltage.
2.8 Initial Start Up
Upon completion of all mechanical mounting and termination of all field wiring, apply system power in the
range of 12-28VDC (24VDC typical) and observe the following normal conditions:
a) FP-624D display reads “0”, and no fault messages are flashing.
b) A temporary upscale reading may occur as the sensor heats up. This upscale reading will decrease to “0”
% within 1-2 minutes of power-up, assuming there is no gas in the area of the sensor.
NOTE: The 4-20mA signal is held constant at 4mA for the first two minutes after power up.
Initial Operational Tests
After a warm up period of 1 hour, the sensor should be checked to verify sensitivity to combustible gas.
Material Requirements
-Detcon PN 600-610000-000 Splash Guard with integral Cal Port -OR-
-Detcon PN 943-000006-038 Threaded Calibration Adapter
- Detcon PN 942-520124-050 Span Gas; 50% LEL methane/balance Air at fixed flow rate of 200-500cc/min.
NOTE: Do not use calibration gases in Nitrogen background gas mixtures. This will cause
significant reading inaccuracies.
a) Attach the calibration adapter to the threaded sensor housing. Apply the test gas at a controlled flow rate
of 200 - 500cc/min (200cc/min is the recommended flow). Allow 1-2 minutes for the reading to stabilize.
Observe that during the 1-2 minutes the display increases to a level near that of the applied calibration gas
value.
b) Remove test gas and observe that the display decreases to “0”.
Initial operational tests are complete. Detcon combustible gas sensors are factory calibrated prior to shipment,
and should not require significant adjustment on start up.
However, it is recommended that a complete
calibration test and adjustment be performed 16 to 24 hours after power-up. Refer to span calibration
instructions in Section 3.4.