Future Design MCT-MC 4.3, User Manual

Page: 16 / 186

MCT-MC
4.3
FDC MCT-MC - 16 - Wiring
3.2.1 Process Loop Controller Communications
The loop controls communicate with the MC touch screen using the RS485 communications port. This allows
up to ten P41/B42 boards to be connected using one 2-wire link. The controllers are wired in parallel with each
one having their own communications address of 1 through 10 (corresponding to loops 1 through 10).
Communication wiring should be run using a minimum of 24 AWG twisted-pair, copper conductors. For short
runs (< 10 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 10 feet, shielded
twisted-pair should be used.
NOTE: 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 can cause erroneous sensor readings or communications errors.
FDC recommends the use of shielded wire for all installations in order to maintain optimum
performance and minimize the possibility of communications errors.
When using shielded twisted-pair, be sure to ground only one end of the cable, preferably at the loop controller.
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.