Detcon TP-424C - Manual (Page 10)

3.7.1 Initial Operational Tests
After a warm up period of approximately 60 minutes, the sensor should be checked to verify proper opera-
tion and sensitivity to H2S gas.
Caution: Initial test and operational procedures require that the sensor junction box cover be removed
and, therefore, negate the electrical classification. De-classify the area before proceeding.
Required Materials
Digital volt/ohm meter
Jeweler’s type screwdriver
Test gas: H2S in Air in the range 25 to 50 ppm. (H2S in nitrogen mixes are not acceptable.)
Detcon P/N 6038 Threaded Calibration Adapter
Detcon P/N 985-241100-321 In-Line Humidifying Tube
a) Remove the junction box cover.
b) Measure the voltage between heater test points (see figure #5). A nominal reading of 5.25 VDC ± 0.1
VDC is acceptable.
c) Measure the voltage between the signal test points: a zero gas reading of 39-40 mv DC is acceptable.
d) Apply 200-500cc/min flow (200cc/min is the recommended flow) of a test gas in the range 25-50 ppm
H2S in Air, using the humidifying tube between the calibration gas cylinder and the H2S sensor.
Observe that the signal voltage increases to a level of 56 mv DC or higher.
e) Remove the test gas and observe that the signal voltage decreases to 39-40 mv DC.
Initial operational tests are complete. Detcon hydrogen sulfide sensors are pre-calibrated prior to shipment
and will, in most cases, not require significant adjustment on start up. However, Detcon recommends that
a complete calibration test and adjustment be performed 16 to 24 hours after power-up. Refer to calibration
instructions in later text.
3.7.2 Remote Mount Heater Voltage Setup
If the sensor has been installed using the remote mounting conf iguration as described in section 3.6, the sen-
sor heater voltage must be adjusted after initial power up. Replacement of the sensor will also require read-
justing the heater voltage. Follow the steps below to set the sensor heater voltage.
Material Requirements
* Digital volt/ohm meter.
a) Declassify the area around the sensor.
b) Remove the junction box cover from the remote sensor enclosure.
c) Using the digital volt/ohm meter, measure the bridge voltage at the remote sensor connector board from
the “White” terminal to the “Black” terminal as shown in figure on page 9. Target voltage is 5.25 volts.
d) At the transmitter, adjust the “TEMP” potentiometer (see figure #5) to achieve a reading of VDC at the
remote sensor connector board as described in item “c” above.
e) Replace the junction box cover on the remote sensor enclosure.
Heater voltage adjustment is complete.
Detcon Model TP-424C Hydrogen Sulfide Sensor PG.10
TP-424C
COARSE
+
PPM H2S
4-20 mADC
T E
X
A
S H
O
U S T
O N
TEMP
HEATER
detcon inc.
SPAN
FINE
SIGNAL
CURRENT
VOLT
SIG
FLT
HTR
FLT Fig. #5