How do I set up MODBUS communication between PM9C Schneider power meter with a generic Modbus software to communicate with my PLC which is Modbus generic?

 

It's a project. Modbus master/clients talk to Modbus slave/servers.

The power meter is slave/server. The PLC needs to be a master/client.

Check out the thread at the link below and substitute
- Schneider PLC for the DCS master/client in the thread
- your brand/model power meter for the VFD in the thread

http://control.com/thread/1411750426

 

Thanks for your response.

I am using a PLC called EDS-3G from circutor which is very easy to program. It is actually meant for energy management systems in industrial applications. Check www.circutor.com .With modbus devices from circutor such as power meters, there is no much involved apart from just putting the peripheral number of the device and the PLC will automatically establish communication with the device via RS485.

Now we have a client who already has power meters installed at their premises but they are from a different manufacturer i.e Schneider electric PM9C power meter. Because their meters already has RS485 output and use Modbus protocol, it is very easy to wire them to our EDS-3G via RS485. The EDS-3G deluxe is Modbus generic and should be able to communicate with the PM9C if all the Modbus settings are correct i.e baudrate, stop bit, address number (peripheral number ) and all the modbus mapping registers have been programmed correctly as indicated in the PM9C data sheet.

The issue is that we have done the wiring between the PM9C and the EDS correctly. All the Modbus settings we have done correctly as shown in the PM9C data sheet but still the ES does not communicate with the power meter.

We are using Powerstudio SCADA software from circutor to program the devices. We have had no issues before to program other generic Modbus devices but this PM9C is causing as trouble.

Please advice

 

1) Are you sure it's a PM9C? The C means ModbusRTU over RS-485. Models without the C do not have Modbus. No hardware/firmware, no Modbus.

2) Have you swapped A and B data lines? First thing you do when there's no comm - swap A and B data lines.

3) The PM9C has a signal common. Does your PLC have a signal line common? If so, try using it.

4) Are you working with a single power meter, not a network?
Networks can have problems that a single meter does not have. When establishing communications, use a single meter, short wire/cable run (bench top if possible) in order to get communications running. After you figure out how to get them talking to each other, then tackle a multidrop network.

5) The meter's slave node ID address is a known number and the master uses the correct slave node ID address, right?
Addressing some other slave node ID address will not get a response. Modbus slaves are silent unless spoken to.

6) Baud rate and parity match?

7) 8 bit RTU data word, not 7 bit ASCII, on both ends, right?

8) Does the RS-485 have blinky LEDs? Is there activity on either end?

9) Can you test the PM9C with a Windows Modbus master program to confirm settings, comm and register addressing? It's takes a lot mystery out of slave implementation.

>We are using Powerstudio SCADA software from circutor to
>program the devices. We have had no issues before to program
>other generic Modbus devices but this PM9C is causing as
>trouble.

I have no clue about the software. It appears from the PM9C instruction sheet that the Modbus slave node address, baud rate and parity can be configured and checked using pushbuttons.

 

Hi David,

Just seen your response very late. Actually you gave all the answers.

PM9C signal common was the issue. I had to wire it up to the PLC signal common to establish the communication.

Can you explain why this was so crucial? Because in almost all cases I have always left it and there is always communication with only A and B.

Thanks.