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If an instrinsic safety barrier self destructs, do not
replace it. Find out what caused the problem. Do not
assume the problem can only be in the indicator.
Only when the problem is corrected should a barrier
be replaced with the exact same brand and type.
2.6.1
Intrinsic Safety Grounding
Special attention must be given to the grounding
system. Without a proper earth ground system,
intrinsic safety barriers will not provide voltage
protection. They must therefore be grounded to a
designated grounding electrode that references the
original power source and instrumentation within the
non-hazardous location.
The yellow/green striped terminal on the end of the
barrier bussbar assembly must be connected to a high
quality source of earth ground which can safely sink
any currents from the barriers in the event of a failure.
This source of ground must be less than 1 Ω from the
true earth ground. Connect this using a #10 or #12
AWG insulated wire through the sealing fitting with
the load cell wiring and terminate it to the ground. If
you choose to use a separate exit point, pack the
sealing fitting and pass the cable through a suitable
strain relief.
2.7
Load Cell Wiring
The load cell wiring from the IQ plus 810 has been
connected to the intrinsic safety barriers at the factory,
(see Figure 2-3). The barriers are located in the
bottom of the enclosure.
Wiring from the indicator is terminated on terminal #1
of the respective barrier. The intrinsically safe output
of the barrier is terminal #3. Sense jumpers at the
indicator have been removed. You must use remote
sensing and jumper the +EX to +SEN and -EX to
-SEN either at the load cell or on the field (#3) side of
the barriers.
The IQ plus 810 can power up to four 350 Ω strain
gauge load cells or eight 700 Ω cells. Connect the load
cell wiring to the appropriate terminals at this time.
From left to right, connect +EX, +SEN, -EX, -SEN,
+SIG, -SIG, and the shield to the bussbar ground.
Installation and Wiring
11
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