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SMC sierra monitor corporation Sentry Instruction Manual - Version 6
SERVICE
Page: 66
7.4 HYDROGEN SULFIDE MODULE (5100-01)
7.4.1 DESCRIPTION
The Hydrogen Sulfide Sensor Module includes the
sensor and electronic assembly installed in an
explosion proof housing. The sensor screws into
one hub of the enclosure and plugs into the bottom
electronics card via a six pin connector. Cabling
to the controller connects to a three pin spring
loaded terminal strip.
When a sensor is changed it is important that the
factors for the new sensor are keyed into the
controller and that a 24 hour stabilization period
elapses prior to voltage adjustments and
calibration. The three factors, each three digits
are written on the sensor connector label.
7.4.2 TROUBLE ANALYSIS
Electrical adjustment, or replacement of the sensor
will be necessary under the following conditions:
• Controller displays the error messages:
CHECK POWER ADJ
SENSOR FAILURE
LOW SENSITIVITY
• False readings or alarms are received due
to sensor inaccuracy.
Warning: During sensor adjustments the concentration
reading on the controller will be inaccurate and alarm
level concentrations may be displayed. If false activation
of the alarm relays will cause a problem disconnect the
relay wiring prior to adjustment or turn the module off
using the CHANGE MODULE mode.
Note:
Although all the necessary data can be collected with a
voltmeter at the sensor module, some helpful
information can be displayed or printed. See diagnostic
codes 0004 and 0008, Appendix C.
7.4.3 ADJUSTMENT PROCEDURE
Prior to reading voltages and making adjustments perform
a visual inspection to confirm that there are no physical
problems such as water in the electronics enclosure,
wiring damage or corrosion.
Use Figure 7-5 to locate test points during the following
procedures.
7.4.3.1 POWER ADJUSTMENT
Comparing to the GND (ground) test point measure the
HEATER VOL (heater voltage) and the HEATER CUR
(heater current) values in VDC. Calculate the power by
the formula: (HEATER CUR - HEATER VOL) * HEATER
VOL / 5.1. The correct value is 400Mw +/- 5 Mw. (Note
that this calculation is performed by the controller and
displayed using diagnostic code 0004.) See Table 7-4 for
corresponding voltage and current settings.
Adjust the heater power using HEATER ADJ potentiometer,
turn clockwise to decrease, counter-clockwise to increase
the power. Make the adjustments 1/4 turn at a time and
wait for the values to stabilize before making successive
adjustments.
7.4.3.2 MODULE ADJUSTMENT
Compare ground to SIGNAL OUT to read the module
voltage. The beginning (no gas) value must be above 1.2
VDC and can be up to 7.5 VDC. If the no gas voltage is
lower than 1.2 VDC adjust using RANGE ADJ
potentiometer.
Figure 7-5
Cover Plate - Hydrogen Sulfide Sensor Module