FAQ’s
What is the most common cause of “Faults”?
o Water ingress into the wiring or FIB’s is the most common cause of
“Faults”.
Why are all the sensors on a bus converter “Faulted”?
o All of the sensors on a CMC Intrinsically Safe network are wired in
parallel. A short circuit on one sensor can short the bus and “Fault”
all of the sensors.
All of the sensors on a single bus converter are indicating intermittent
“Faults” every once in a while?
o The bus may have a partial short circuit. Partial short circuits can
occur after severe electrical storms or due to water ingress in the
wiring. Follow the procedure in the flowchart but instead of observing
the LED’s, observe the voltage on the blue/white and green/white
pairs. Both pairs should have 4-5VDC present, with the negative
lead on the white wire and the positive lead on the colored wire.
o You can make a test cable from an old sensor. Join the white and
black wires together and measure between the white/black wires
and the green (data) and red (power) wires. The test cable can be
plugged into a spare jack in the FIB for testing.
o As indicated in the flow chart, start at the first FIB after the bus
converter and work outwards. If the voltages return to normal when
the outbound cable(s) is disconnected using the disconnect
switches, then the partial short is further down the network. If the
voltages do not return to normal, disconnect the sensors one a time
to locate the partial short.
A sensor reads +85
o
C or +185
o
F, what is wrong?
o The red wire in the sensor cable is open. Unplug the sensor and
clean both the plug and jack with 99% Isopropyl Alcohol. Replace
the sensor if the problem is not resolved.
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