Detcon FP-624D-HT - Manual (Page 16)

Model FP-624D-HT
FP-624D-HT Instruction Manual Rev. 1.1 Page 12 of 44
AWG Maximum Separation (feet)
20 50
18 75
16 125
14 175
Reference Figure 11 for wiring diagram. Also note the jumper that is required on the remote sensor connector
board. Failure to install this jumper will cause a sensor fault condition.
Figure 11 Remote Sensor Wiring Diagram
2.7.1 Bridge Voltage Adjustment
When a sensor is remote mounted, consideration must be given to the lengths of cable used and how it affects
the sensor bridge voltage. Differing lengths of cables will have varying amounts of resistance which will shift
the sensor bridge voltage. Because of this, the bridge voltage will need to be adjusted after initial power up.
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-HT 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