AccuEnergy AcuRev 2000, User Manual

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Communication
AcuRev 2000 communication utilizes RS485 port, via Modbus-RTU protocol. The wiring
terminals are A, B, S(1, 2, 3). "A" is called differential signal " ", "B" is called differential
signal"-", "S" is connected to the shielding of shielded twisted pair cable. The maximum
distance of Shielded Twisted Pair cable is 1200 m. The distance will be shorter if more
devices are on the same communication link or using a higher baud rate.
If the master device does not have RS485 but RS232 port, a RS232/485 converter can be
utilized. Typical RS485 network topologies include line, circle and star (wye).
In order to improve communcation quality, please pay attention to:
1. High-quality Shielded Twisted Pair cable is very important, AWG22 (0.6mm
2
) or lower is
recommended. Two cables should be different colors.
2. Pay attention to "single point earthing". It means there is only one point of the shielding
connected to ground in a single communication link.
3. Every A(+) should be connected to A(+), B(-) to B(-), or it will infuence the network, even
damage the communication interface.
4. "T" type connection topology should be avoided. This means no new branches except
from the starting point.
5.Keep communication cables away as much as possible from sources of electrical noise.
When several devices are connected (daisy chain) to the same long communication line, an
anti signal refecting resistor (typical value 120O- 3000Ohm, 0.25W) is often used at the end
of the circuit (the last meter of the chain) if the communication quality is distorted.
6. Use RS232/RS485 or USB/RS485 converter with optical isolated output and surge
protection.