We are using Schneider Electric's 174-CEV-300-10 Ethernet Bridge on a Modbus RTU protocol RS485 2-wire bus to communicate with 13 DMMS 300+ Power Meters. The meters respond one at a time and polling is not possible for more than 1 meter at a time.

Main protocol is ModbusTCP and the Ethernet converter, being master, communicates with slave devices (power meters). Modbus runs on standard 2-wire RS485, connecting all 13 power meters. Each power meter is configured with unique ID no. Each Meter data communicates independently when polled, but any 2 meters fail to communicate or poll the data together. Anyone knows the solution? If any configuration should be changed for the Ethernet converter?

 

We use a similar process to communicate with a set of 10 and a set of 11 Schneider Merlin Gerin SEPAM protection relays that communicate via a two wire RS485 MODBUS network. The software is part the a QUANTUM PLC system controlling a diesel generator process. The PLC connected to the Ethernet sends comms to a CEV bridge similarly. The data being returned is 75 words of which we use approx. 50 words. Within Quantum we use the function MPB_MSTR. IT is possible to have up to four such functions enabled at once, we do not use more than one at a time however. We operate on a 15 second scan time with each function enabling the following function on completion. Completion is established by either a true successful read or termination because the one read has take 5 seconds (read not successful). For 10 relays however the operation takes about 10 seconds. We have no problems with this. Reading one relay at a time on a bus network may be enough. Also we do not believe a two wire RS485 connection could handle more than one at a time.
This may help. Regards

 

Hello,

Not quite sure what you mean with 2 slaves doing what?

But with the bridge configured as a slave device and the slave address set to 0 (In the Advanced Modbus Protocoll Settings)you should be able to reach any of the power meters by using it's Modbus address. See page 12 of the Modbus to Ethernet bridge user guide 890USE15500.

Hope this helps

Regards

Gijsbert-Jan Welp,
Technical Support Automation,
Schneider-Electric Netherlands.

 

Is the CEV 300 configured properly for slave address?

Slave Device: Slave device parameters are:
Slave Address (0 for auto, or 1...255 fixed)

Slave Address
The Bridge’s Slave Address parameter specifies how the Bridge will direct messages
received from Ethernet to a Slave device at the serial port.
Each message originated from a Modbus Master contains a Unit_ID field that
addresses a Modbus Slave destination device. The Bridge can be configured to use
that Unit_ID address as received, or to substitute a fixed address instead.
Setting the Slave Address parameter to 0 (zero) configures the Bridge to use the
Unit_ID field as received in the message. It will pass the message out its Modbus port
to the Slave device addressed in the Unit_ID field.
Setting the Slave Address parameter to any non–zero value causes the Bridge to
always use that fixed value as the Slave address for all messages sent out its Modbus
port, regardless of the Unit_ID contained in the message. This routes all messages to
a single device.
The allowable non–zero range for entering this value is 1 ... 255 decimal. Note that
Modbus Slave addresses are valid in the range 1 ... 247 only.
The default is 0 (zero), specifying the Bridge to use the received Unit_ID field.

 

I interpret your message in he following way.
You may be able to talk to every meters one at a time but not to several, one after another. If I am right, try to insert a delay between requests.

Start with half a seconds. I am not positive that you are talking about the same power meters but I had a problem in the past with some. The meters needed some time to turn around after replying to a request. The solution was to insert a delay or to upgrade the meters.

 

Also remember that there is a limit of 8 concurrent connections on the Ethernet side.

 

Another solution is to go with the Electro Industries DMMS350. This unit has built-in Ethernet and you communicate to all meters at the same time. It is a new product for us.