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MCT-CM
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3.4 Connecting to the MCT Process Loop Controls
The MCT-CM can support up to 10 individual control loops. The controls communicate with the MCT control
module using RS485 serial communications. This allows all loop controls to be connected using one 2-wire
link. The controllers are wired in parallel with each one having a unique address from 1 to 10 (corresponding
to loop number 1 - 10).
NOTE: Refer to
loop control’s operating manual for proper power, communications and sensor connections.
It is important to keep the power/control and sensor/communications wiring separated from one
another. Relay and/or high voltage outputs can interfere with the sensor and communication wiring
as they cycle on and off, which could erroneous sensor readings or communications errors.
3.4.1 Communication Wiring
Communications wiring must be run using a minimum of 24 AWG twisted-pair, copper conductors. For short
runs (< 50 feet total), non-shielded wiring can be used as long as proper separation from power/control
conductors is maintained. For communications wiring where the total length will exceed 50 feet, shielded
twisted-pair must be used.
When using shielded twisted-pair, be sure to ground only when end of the cable, preferably at the control
module. Allowing any other portion of the cable shield to come in contact with ground, or grounding both ends,
will cause ground loop currents to flow in that section of the cable shield which can disrupt communications.
NOTE: FDC recommends the use of shielded wire for all installations in order to maintain optimum
performance and minimize the possibility of communications errors.
3.4.1.1
FC6A-SIF52 Communication Card to Loop Controls
Communications Wiring Example (FDC-9300 controller shown)