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SMC sierra monitor corporation Sentry Instruction Manual - Version 6
SERVICE
Page: 74
7.7 CARBON MONOXIDE MODULE (5100-04)
7.7.1 DESCRIPTION
The Carbon Monoxide 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 from the controller
connects to a three pin spring loaded terminal
strip.
7.7.2 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.
7.7.3 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 7-8 to locate test points during the following
procedures.
7.7.3.1 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
SENSITIVITY ADJ potentiometer to adjust the voltage
based on the following:
• 1 ppm CO = 0.004 VDC.
• 100 ppm CO = 0.40 VDC.
• 250 ppm CO = 1.00 VDC.
7.7.3.2 SENSOR REPLACEMENT
The carbon monoxide 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 Carbon
Monoxide 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.
Figure 7-8
Cover Plate - Carbon Monoxide Module