Detcon FP-100 - Manual (Page 16)

Model FP-100
FP-100 Instruction Manual Rev. 0.0 Page 12 of 30
2. A temporary upscale reading may occur as the sensor stabilizes. This upscale reading will decrease to
“0” ppm (40mV on the DVM) 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 (or when zero has stabilized), the sensor should be checked to verify
sensitivity to the target gas.
Material Requirements
-Detcon PN 613-120000-700 700 Series Splash Guard with integral Cal Port, with Wind Guard -OR-
-Detcon PN 943-000006-132 Threaded Calibration Adapter.
-Detcon PN 942-520124-050 Span Gas; 50% LEL methane/balance Air at fixed flow rate of 200-500cc/min.
-DVM (if a 100 Series Display is not installed)
NOTE: Do not use calibration gases in Nitrogen background gas mixtures. This will cause
significant reading inaccuracies.
1. If the sensor has a loop power display installed, the display should read “0”. If a DVM is used to
measure the 4-20mA output, set the DVM to measure millivolts and connect the leads across TP1 and
TP2 on the terminal board. The DVM will read the voltage drop across a 10Ω resistor. The resistor
develops a 10mV voltage drop per 1mA of current. Thus a reading of 40mV on a DVM equals 4mA
of current. The DVM should read 40±2mV.
2. Attach the calibration adapter to the Bottom Housing or connect tubing to integral cal port. It is
recommended that the Wind Guard (Detcon P/N 943-000000-000) in installed over the Splash Guard
during calibration. Apply the test gas at a controlled flow rate of 200 - 500cc/min (500cc/min is the
recommended flow). If the sensor has a display, the reading should increase to 50% of full range.
Observe that the DVM increases to a level near that of the applied calibration gas value. Typically this
would be 50% of full range, a reading of 120±2mV (12mA)
3. Remove test gas and observe that, if the sensor has a loop power display installed, the display
decreases to “0.0”. If a DVM is used the DVM reading should decrease back to 40mV (4mA).
4. If a calibration adapter was used during these tests, remove them from the unit, and re-install the
Splash Guard. If a wind guard was used, remove the wind guard.
Initial operational tests are complete. FP-100 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 zero and span calibration
instructions in Section 3.2 Calibration.