Compac CNG Service Manual page 102

C4000 Microprocessor Board
RS485 MOD-BUS Wiring for Micro Motion Meter
C4000 Power Supply
Compac Industries Ltd.
Electrical Drawings and Component Details
The following changes are made to standard Compac dispensers to allow
the use of RS485 communication with a Micro Motion meter.
1. An RS485 Board is fitted inside the Power supply flame proof box.
2. The IS cable pinouts will need to be changed to match the wiring
detailed below.
3. An extra red wire will need to be added to link pin 5 on J1 to pin 3 on J5.
4. The IS cable will need to have The Red / Black / White cable removed
from J2A and put into pin 6 of J2B.
5. A new plug will need to be made for J13 and the Black/Red and
White/Black/Red wires removed from J2A and inserted into pins 5 and 9
as shown below.
6. Special software to support the Micro Motion CNG50 meter will need to
be installed. Please contact the Compac Helpdesk for the latest version.
7. Connect the RS485 cable to the terminals on J12 as follows:
TXDP to RS485A
DTRP to RS485B
GND to GND
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