Multi function meter looping
we have to design system for Energy monitoring system.
We have 70 Multifunction meter in a different-different location we have to take data over SCADA ,and all multifunction meter are equiped with RS485 protocol. distance between one meter to another is approx 90 meter.
my question is
1-how many meters will be looped in a single loop
2-is required PLC for every loop or we can use one plc for all meters
Voted best answer
Your question is not clear, as mentioned in other post here. You should explain what is the protocol used, RS-485 is the transmission line, but the protocol is most probably Modbus RTU. Profibus-DP is also based on RS-485 line, like other field protocols.
Also it is not defined if you need the data from devices to go in the PLC or directly in your SCADA. Like other users explained, usually one RS-485 port in the PLC can handle max. 32 nodes and 1200 m line lenght (point to point) without repeaters - in IDEAL case !
I could suggest to look in the Net for RS-485 repeaters. For example, the figure below presents example for Active Star Wiring Hub, which converts one RS-485 line into tree independent RS-485 lines, each for 32 nodes and 1200 m max distance (as described for the hub).
Also there are similar USB to RS-485 transmitters, so you can enter the signals directly to your PC by means of COM port, then use the signals directly to your SCADA.