Sentry Industries 5000 User Manual

 

 

The Oxygen Module includes the  electronic 
assembly installed in an explosion proof housing 
and the electrochemical sensor connected to one 
hub of the enclosure. Cabling from the controller 
connects to a three pin spring  loaded terminal 
strip. 

Electrical adjustment, or replacement of the sensor 
will be necessary under the following conditions: 

• 

Controller displays the following error 
messages: 

• 

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. 

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  7-7 to locate test points during the following 
procedures. 

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 

 (pos) and 

 (ground) and use 

 potentiometer to set the voltage equal to 

1/10 of the actual oxygen concentration.  In clean air the 
concentration is 20.9% so the voltage should be set at 
2.09 VDC. 

The oxygen sensor should be replaced when it can no 
longer be calibrated correctly or when the signal output 
drops to zero.  Generally this is every twelve to eighteen 
months.  The Sentry clock keeps track of the age of the 
sensor if it is correctly initialized in the "change module" 
mode. 

When a new sensor is installed use the 

 

menu selection to answer yes to the "new sensor?" 
question.  After nine months the 

 

message will be displayed to warn that a new sensor 
should be installed. 

The 

 message for Oxygen 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. 

When sensor replacement is required, open the cover of 
the sensor module, remove the transmitter and disconnect 
the sensor wiring harness from the back of the transmitter.