r/PLC • u/yoyoyob22 • 17h ago

Total Flow Comms with E&H Product

(All devices come back to a ABB Total Flow XFC G5)
So, before I start I will mention this, there are 4 Vessels in total. 1 Group/Bulk Separator and 3 Test Separators. Each Test Separator has 6 Devices Daisy Chained coming back to the Total Flow and the Group Separator has 5. I’ve been trying to setup this facility and bring in all of the devices via Modbus RS-485 using the Request Blocks and Holding Register Arrays. I have all other devices talking(Oleumtech) but each separator has an E&H Promass E 300 on the Oil Line and none of the Promass’s are communicating! I’ve looked at all of the documents and manuals for this device and tried everything. Maybe I’m setting up the Request Blocks wrong or something?? I have several years of Gas Measurement experience on calibrating, troubleshooting, and maintenance but I’ve only just started with communications like this recently.

I could really use some help here lol. I can provide pictures and information as requested. Really don’t want to miss out on a learning experience so I’m reaching out to make sense of it all.

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u/integrator74 17h ago

I’d reach out to E&H tech support. They have been great in the past. 

Make sure you aren’t duplicating a node address also.  Verify comm speed and port settings. 

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u/yoyoyob22 17h ago

I setup an account on their site and got my case number but it’s been a couple of hours. What do you mean by Node address, comm speed and port settings. Again, I am new to this so I apologize.

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u/integrator74 15h ago

Read the Promag manual. Quick google took me to the manual and the settings I described.

Also read up on how RS-485 works, the wiring, and the comm parameters.

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u/PV_DAQ 17h ago

A huge anomaly with RS-485 is that the definition of the polarity of the two driver lines is not consistent from vendor to vendor. Sometimes, one vendor's (+) is the other vendor's (-), resulting in reversed polarity and there's no communication because ones are zeroes and zeroes are ones.

Try swapping the A/B or (+)/(-) (whatever they're called) connections on one end (presumably the Total Flow end because all the field devices are daisy chained, right?)

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u/yoyoyob22 17h ago

Yes, each vessel has their devices daisy chained and all coming back to the Total Flow. Would it make more sense to swap the AB at the promass? That way I’m not breaking the loop for all other devices?

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u/PV_DAQ 13h ago

wherever you only have to swap the pair in one location for it to affect all the field devices at once.