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Hi everyone
This is my first message at control.com, but I've been reading here for a while. Seems to be a great site.
I'm an electrician in my daily work, and have stumbled upon an interesting problem which I'm supposed to solve.
We have a SCADA system which includes supervising of electrical power flow for a residential building. The subsystem consists of:
1 x Moxa Mgate MB3180 ethernet/serial interface
1 x Schneider power meter PM750
27 x Carlo Gavazzi EM24 power measurements.
They are interconnected through daisy-chain 2-wire RS485 which are running Modbus RTU. The problem seem to be that the Schneider PM750 destroys the communication on the line.
Through a web interface communicating with the Moxa Mgate, I got the message "Illegal Package (CRC)" with the PM750 is connected. This is true for every component on the bus. When the PM750 not connected (identical wiring), there are no error message, and the communication works as intended.
I've checked the baud rate, parity and adresses of components, but haven't found the solution to the problem yet.
I've also experimented a bit with different physical configurations regarding terminating resistors and shield termination. Since the wiring is identical when the communication works and when it don't work, I'm suspecting the Schneider PM750 to be erronous. I've also monitored the bus activity on oscilloscope and the physical signals seem to be fine.
The PM750 is located as the last component on the wiring, and this setup have been working for some time. We have almost identical setups in different buildings which are working, but there the PM750 is located at the beginning of the bus wiring.
I haven't experimented with line biasing or isolating the PM750 through RS485 repeater.
I would appreciate any thoughts to the problem!
This is my first message at control.com, but I've been reading here for a while. Seems to be a great site.
I'm an electrician in my daily work, and have stumbled upon an interesting problem which I'm supposed to solve.
We have a SCADA system which includes supervising of electrical power flow for a residential building. The subsystem consists of:
1 x Moxa Mgate MB3180 ethernet/serial interface
1 x Schneider power meter PM750
27 x Carlo Gavazzi EM24 power measurements.
They are interconnected through daisy-chain 2-wire RS485 which are running Modbus RTU. The problem seem to be that the Schneider PM750 destroys the communication on the line.
Through a web interface communicating with the Moxa Mgate, I got the message "Illegal Package (CRC)" with the PM750 is connected. This is true for every component on the bus. When the PM750 not connected (identical wiring), there are no error message, and the communication works as intended.
I've checked the baud rate, parity and adresses of components, but haven't found the solution to the problem yet.
I've also experimented a bit with different physical configurations regarding terminating resistors and shield termination. Since the wiring is identical when the communication works and when it don't work, I'm suspecting the Schneider PM750 to be erronous. I've also monitored the bus activity on oscilloscope and the physical signals seem to be fine.
The PM750 is located as the last component on the wiring, and this setup have been working for some time. We have almost identical setups in different buildings which are working, but there the PM750 is located at the beginning of the bus wiring.
I haven't experimented with line biasing or isolating the PM750 through RS485 repeater.
I would appreciate any thoughts to the problem!