4.1.2.4 Pellistor Only Gas detectors
Connection Procedure
Note: For use in hazardous areas, the pellistors must be housed in an Exd enclosure mounted on
an Exe terminal housing.
• DO NOT connect the pellistors at this time.
• Remove the grey protective cover from the appropriate input module.
• Configure the jumper switches as shown below (i.e. J8 & J9 switched ON, all others OFF)
• Connect a voltmeter between pins 22 (+V) and 24 (0V).
• Adjust VR1 and VR2 until the correct voltage can be measured for the pellistors being
used (SSCL pellistors require 2.0V 0.01V).
VR1 & VR2 provide coarse and fine output voltage adjustment respectively.
Note: Connecting a voltage of greater than 2.2V will cause irreparable damage to the
pellistors.
• Connect the pellistors to the input module observing the above diagram.
• Check that the voltage across the pellistors remains at 2.0V 0.01V, adjust if necessary.
Note: Measure the voltage at the pellistors, not at the input module terminals.
• Refit the grey protective cover.
• Perform software configuration (refer to ‘MCU Software Configuration and System
Calibration Manual’).
• Perform system calibration.
If EARTH continuity is not
maintained via gland (e.g.
plastic gland) then connect
cable screen or armour to
EARTH terminal as shown.
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