Micrologix 1400 modbus comms with E&H Promass 83 Meter

mvillarreal

Member
Join Date
Jul 2014
Location
Sinton, Texas
Posts
3
I am having trouble communication with 2 devices with the micrologix 1400. I am using the 485 to mil1100 comm cable to communicate with a omni 3000 currently. omni address is currently 1 and is working fine, when i set up another message with address 2 which is the E&H Meter, it kills my 1st message going to the omni. I have also tried just to communicate with just the E&H meter and have been unsuccessful.

Any help on this would be appreciated, Thanks
 
make sure that both of your messages arent going active at the same time. how fast are you trying to poll? I would use a timer after polling the first device and then wait a few seconds and then poll the next device.
 
I work with E+H meters all the time so this is right up my alley. Are you sure that your meter has Modbus as a option? I know you can order meters in several different configurations and Modbus is not a default.

If you are not able to talk to the meter by itself then you may not have the wiring or the programming in the meter correct for your modbus settings in your PLC.

I have done this with a 1400 before and it worked just fine. Attached is a screenshot from my program.

Promass Modbus.jpg
 
One thing you may want to do is use a program like Modbus Poll to act as the Modbus master so you can check your meter’s ability to communicate and to setup and confirm the setting. When having problems communicating with equipment I like to take things down to the basic components and get them working by themselves before combining everything. Just a thought.
http://www.modbustools.com/modbus_poll.html
 
I have seen this symptom when using RS485 with improper termination at ends of the line or when one of them was not wired properly.

I have also decided not to worry about the data pin specs manufactures give for their RS485 ports, and just use the trial and error method to determine whether RX+ goes to B+ or B- or whatever else the mfg. decide to call the pins. Ground and common I do care about but the names of the data lines is a coin flip.
 

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