SMC sierra monitor corporation Sentry Instruction Manual - Version 6
SERVICE
Page: 81
7.10 AMMONIA SENSOR MODULE (5100-25)
7.10.1 DESCRIPTION
The Ammonia Sensor Module includes a sensor
assembly and electronic assembly installed in an
explosion proof housing.
The sensor assembly includes a rechargeable
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.
7.10.2 TROUBLE ANALYSIS
Electrical adjustment, recharge, 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.
7.10.3 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 7-13 to locate test points during the following
procedures.
7.10.3.1 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% of full scale = 0.02 VDC.
• 100% of full scale = 2.00 VDC.
7.10.3.2 SENSOR RECHARGE
The Ammonia sensor can be recharged by removing it
from service, draining electrolyte, cleaning electrodes and
replacing the electrolyte and membrane.
Step by step instructions for sensor recharge are supplied
with the recharge kit.
7.10.3.3 SENSOR REPLACEMENT
The Ammonia sensor assembly should be replaced when it
can no longer be recharged and calibrated correctly.
Figure 7-13
Cover Plate - Ammonia Module