Roughneck™ motherboard, Figure 6 – Detcon H2S RoughNECK User Manual
Page 7
6.1 Heater Voltage Check
After a warm up period of approximately 15 minutes, the sensor heater voltage should be checked. Because
different installations will require differing lengths of cable, a significant voltage drop can occur in the con-
ductors that carry the sensor heater voltage. This voltage change can affect calibration and should be
checked and adjusted if necessary after installation.
Note: If a RoughNECK™ system has been calibrated using the same cable lengths as those in the installa-
tion then the heater voltage should not be affected and adjustment will typically not be necessary.
Use the following procedure to check and adjust the sensor heater voltage:
Required Materials
Digital volt/ohm meter
Jeweler’s type screwdriver
Note: The goal of this procedure is to have a heater voltage reading of 5.2 V, ± .25V at the sensor.
a) Remove the sensor junction box cover of sensor #1.
b) At the sensor junction box connector, measure the voltage between the white (+) and black (–) wires
(see fig. 4). If the voltage is between 4.95 and 5.45 volts no adjustment is necessary. If it is outside these
limits make note of the voltage and proceed to item “c” below.
c) Measure the voltage of sensor #1 at the RoughNECK™ motherboard between test points TP4 (+) and
TP5 (–) (see fig. 5). Subtract the reading at the sensor from the reading at the motherboard (this will
give you the amount of the voltage drop across the cable.)
d) Add the voltage drop to 5.2 and then set the heater voltage, as measured between test points TP4 (+)
and TP5 (–), to that number. Adjust the voltage via the sensor heater potentiometer “P5”. This proce-
dure will give you 5.2 V at the sensor.
Detcon RoughNECK™ H2S Gas Detection & Alarm System PG.7
12VDC
IN
BLU
YEL
BLK
WHT
SENSOR 1
SENSOR 2
BLU
YEL
BLK
WHT
HORN
PWR
STROBE
ON
OFF
SW1
CURRENT 1
TP2
TP3
HEATER 1
TP4
TP5
SIGNAL 1
TP6
TP7
CURRENT 2
TP11
TP12
HEATER 2
TP13
TP14
SIGNAL 2
TP15
TP16
SPAN 1
SPAN 2
P5 HEATER 1
P6 HEATER 2
TP9
TP10
COM
HIGH
TP8
LOW
TP1
SIGNAL
P4
HIGH
HORN
P3
LOW
STROBE
RoughNECK™ Motherboard
Figure 6