Detcon H2S RoughNECK - Manual (Page 8)

Example: You measure 4.9 V at the sensor and 5.2 V at the motherboard. The difference is .3 V. Add
that to 5.2 V to arrive at 5.5 V. Set the heater voltage at the motherboard to 5.5 V.
e) If applicable repeat the procedure for sensor #2.
6.2 Initial Operational Tests
After the sensor heater voltage has been checked and a warm up period of approximately 30 minutes has
been allowed for, the sensor(s) should be checked to verify proper operation and sensitivity to H2S gas.
Required Materials
Digital volt/ohm meter
Jeweler’s type screwdriver
Test gas: H2S in air in the range 20 to 80 ppm. H2S and nitrogen mixes are not acceptable.
Detcon calibration adapter, PN6038
a) On sensor #1, apply a test gas in the range 20-80 ppm H2S in air. After a brief period observe that the
alarm strobe and horn fire (this is assumming alarm set points of 10 ppm and 15 ppm).
b) Remove the test gas and observe that the alarm strobe and horn go off.
c) If applicable, repeat steps “a” and “b” with sensor #2.
Note: If the strobe and/or horn failed to fire proceed to section 7.0, “Calibration”.
Initial operational tests are complete. Detcon RoughNECK™ H2S detectors are pre-calibrated prior to ship-
ment and will, in most cases, not require significant adjustment on start up. However, Detcon recommends
that a complete calibration test and adjustment be performed within 24 hours of installation. Refer to cali-
bration instructions in later text.
7.0 C ALIBRATION
Note: Detcon solid state MOS hydrogen sulfide sensors give erroneous readings in oxygen depleted envi-
ronments. Calibration gas mixtures of H2S and air are required. Do not use span gas cylinders with nitro-
gen and H2S mixtures.
Material Requirements
Digital volt/ohm meter
Jeweler’s type screwdriver
Detcon PN 6038 Threaded Calibration Adapter
Span Gas: 20 ppm H2S in air at a controlled flow rate between 100 and 1,000 ml/min.
NOTE: Span gas mixtures in the range 20 to 80 ppm are acceptable but 20 to 40 ppm is recommended
to provide the best signal linearity. Span gas mixtures less than 20 ppm are not recommended as these
will reduce the accuracy of signal linearity.
a) Check and adjust the sensor heater voltage as instructed in section 6.1.
b) Measure the signal voltage of sensor #1 between signal test points TP6 (+) and TP7 (–). A zero gas read-
ing of equal to or less than 1V is expected.
c) Remove the rain shield from sensor #1 and attach the threaded calibration adapter.
d) At a flow rate of between 100 ml/min to 1000 ml/min, apply a gas standard of 20 ppm. Wait 3-5 min-
utes for signal stability.
e) Using the Span 1 potentiometer, adjust the signal to a reading equal to the level as reflected in the cali-
bration table below.
f) Remove the gas standard and calibration adapter. Observe that the signal decreases to ≤1 V within 3-5
minutes.
Detcon RoughNECK™ H2S Gas Detection & Alarm System PG.8