Detcon H2S RoughNECK User Manual

Page 10

If the ambient temperature is 72° F, the desired power setting should be 218 mW, ±3%. On hotter days
when the ambient temperature is 100°F, the optimal power setting should be 207mW, ±3%. A cold day
with an ambient temperature of 32°F, would call for a power setting of 238mW, ±3%.

To set the sensor heater for power rather than voltage, follow the instructions below.

Note 1:

Power (P) is the result of multiplying the heater voltage “VOLT” (V) by the heater current “CUR-

RENT” (I). P = V x I

Note 2:

Because the heater current is routed through a 1 ohm resistor located between the test points labeled

“CURRENT”, it is not necessary to set your volt/ohm meter to measure current to obtain the proper reading. Your
meter should be set to measure millivolts and the reading is simply interpreted as heater current in milliamps.

1 - Measure the heater voltage at the test points labeled “HEATER”. (example - 5.2V @ 72°F)
2 - Next, measure the heater current at the test points labeled “CURRENT”. (example .043 A)

Thus, 5.2 (volts) x .043 (amps) = .223 (watts or 223 milliwatts). This falls within 3% of the target power set-
ting of 218 mW and is acceptable. If the value was too low, you would increase the voltage by turning the
potentiometer labeled “HEATER” clockwise, and then recalculate with the new voltage and current read-
ings. If the value was too high, you would decrease the voltage and repeat the process as necessary to reach
the desired power setting.

9.0 S

ETTING

LARMS

The alarm strobe and horn are factory set at 10 ppm for the low alarm (strobe) and 15 ppm for the high
alarm (horn). The strobe and horn specifications are listed in section 4.0. Each alarm can be set indepen-
dently over the range of 10 to 90 ppm. To set the alarm strobe and horn follow the instructions below.

LOW ALARM - STROBE SET
a) Insert your volt meter probes into TP8 (+) and TP10 (–).
b) Use the low alarm - strobe potentiometer (P3) to adjust the reading to the desired alarm set point as

indicated in the table below

PPM

V DC

1.4

1.6

1.8

2.2

2.4

2.6

2.8

3.2

3.4

3.6

3.8

4.2

4.4

4.6

HIGH ALARM - HORN SET
a) Insert your volt meter probes into TP9 (+) and TP10 (–).
b) Use the high alarm - strobe potentiometer (P4) to adjust the reading to the desired alarm set point as

indicated in the same table.

Detcon RoughNECK™ H2S Gas Detection & Alarm System PG.10