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SMC sierra monitor corporation Sentry Instruction Manual - Version 6
SERVICE
Page: 76
7.8 HYDROGEN SULFIDE MODULE (5100-05)
7.8.1 DESCRIPTION
Model 5100-05 Hydrogen Sulfide Sensor Module
includes a sensor assembly and electronic
assembly installed in an explosion proof housing.
The sensor assembly includes a reuseable housing
and disposable electrochemical sensor. The
assembly screws into one hub of the sensor
module enclosure and plugs into the bottom
electronics card via a six pin connector.
Cabling from the controller connects to a three pin
spring loaded terminal strip on the electronics
assembly.
7.8.2 TROUBLE ANALYSIS
Electrical adjustment, or replacement of the sensor
will be necessary under the following conditions:
• Controller displays the following error
messages
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 on the controller or
printed. See diagnostic codes 0004 and 0008 in
Appendix C.
7.8.3 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 7-9 to locate test points during the following
procedures.
7.8.3.1 SIGNAL ADJUSTMENT
It is unlikely that any electrical adjustment will be
required except when a new sensor is installed.
To make the electrical adjustment connect a voltmeter to
SIGNAL OUT (pos) and GND (ground) and use SPAN ADJ
potentiometer to adjust the voltage based on the
following:
• 1 ppm H
2
S = 0.02 VDC.
• 100 ppm H
2
S = 2.00 VDC.
7.8.3.2 SENSOR REPLACEMENT
The Hydrogen Sulfide sensor should be replaced when it
can no longer be calibrated correctly. Generally this is
every twenty four to thirty months.
The SENSOR FAILURE message for Hydrogen Sulfide
sensors does not indicate a specific failure of the sensor
but indicates that the sensor is not correctly connected to
the electronics. If this message appears check that the
sensor harness is correctly installed to the connector on
the bottom electronics board.
The gas sensor which is located inside the sensor
assembly housing can be replaced without replacement of
the housing. To replace the sensor:
Figure 7-9
Cover Plate - Hydrogen Sulfide Module