Relay - Pc Connection For Rs232 Front Port; Communications - GE Multilin F650 Instruction Manual

1.3 ENERVISTA F650 SETUP SOFTWARE 1 GETTING STARTED
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Figure 1–16: RELAY- PC CONNECTION FOR RS232 FRONT PORT
To minimize errors from noise, the use of shielded twisted pair wire is recommended. For a correct operation, polarity must
be respected, although if it is not so, there is no danger to damage the unit. For instance, the relays must be connected with
all RS485 SDA terminals connected together, and all SDB terminals connected together. This may result confusing
sometimes, as the RS485 standard refers only to terminals named "A" and "B", although many devices use terminals
named "+" and "-".
As a general rule, terminals "A" should be connected to terminals "-", and terminals "B" to "+". The GND terminal should be
connected to the common wire inside the shield, when provided. Otherwise, it should be connected to the shield. Each
relay should also be daisy chained to the next one in the link. A maximum of 32 relays can be connected in this manner
without exceeding driver capability. For larger systems, additional serial channels must be added. It is also possible to use
commercially available repeaters to increase the number of relays on a single channel to more than 32. Do not use other
connection configuration different than the recommended.
Lightning strikes and ground surge currents can cause large momentary voltage differences between remote ends of the
communication link. For this reason, surge protection devices are internally provided. To ensure maximum reliability, all
equipment should have similar transient protection devices installed.
1-16 F650 Digital Bay Controller GE Multilin