Instruction manual

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