Flowmeter supporting Ethernet Modbus TCP/IP


Thread Starter


Customer is replacing a Rockwell ControlLogix system with a Modicon Unity Quantum for a process control application.
We need to install two (2) flow meters for natural gas supporting Ethernet Modbus TCP/IP protocol. Can someone provide us with a vendor list?

Thanks in advance.

For the records, customer stated Modicon Unity Quantum is currently the best PLC in the market for process control!
You can ask Endress and Hauser, they maye have something. Are you sure with the Ethernet TCP /IP on Fieldbus? Why don't you ask Profibus-DP Flowmeter quote from Endress and Hauser?
Quantum Unity CPU supports Profibus DP card in the local rack. This network is more reliable for Process value reading, discrete I/O handling. Even Profibus PA can be connected !!!
Check the Profibus Quantum card provider,
Prosoft company. http://www.protalkq.com/content/view/full/6999

Good Luck.

Robert Dusza

You might want to look at the Arcom DS1 series of gateways. We have used one of these units at a Zone Pumping Station to translate between
HART & MODBUS RTU for a number of years with good success. This prevented us from having to invest in new flow meters because of the
protocol change. The are at http://www.arcom.com .


Robert J. Dusza, Jr.
Project & Technical Support Manager
(V) 1-860-647-3219
(F) 1-860-647-3150
E-mail - [email protected]
Manchester Water & Sewer Dept.
125 Spring St. P.O. Box 191
Manchester, CT 06045-0191
Typically you will not find Ethernet connection in a field instrument such as a flow meter. The reason is that Ethernet only runs 100 m, and flow meters are very often further away than that. Moreover, Ethernet requires dedicated wires and does not provide power for the flow meter etc. Very often the flow meter is in a hazardous area demanding intrinsic safety, which cannot be met by Ethernet.

Therefore flow meters and other instrumentation instead use a fieldbus protocol such as HART, Foundation fieldbusT H1, or Profibus-PA. These protocols meet the needs of field instrumentation, such as very long distance, bus power, intrinsic safety, and passive multidrop connection.

Ethernet is usually used in the control room where distances are short.

All modern flow computers have Ethernet. Perhaps this is what you are thinking of? Modern flow computers use HART, Foundation fieldbusT H1, or Profibus-PA to connect to the flow meter in the field. But the flow computers connect to the control system and data servers through Ethernet.

For more on where fieldbus vs industrial Ethernet is used, and how, take a look at the yellow book "Fieldbuses for Process Control: Engineering,
Operation, and Maintenance" buy online:

Jonas Berge
[email protected]
Learn fieldbus and Ethernet at your own pace: www.isa.org/fieldbuses
Learn OPC and automation software at your own pace: www.isa.org/autosoftware

Standard Plan

Most any quality gas meter can be interfaced with a variety of aftermarket modules to get this protocol. When we apply our meters in this fashion we may also go through an inexpensive PLC to achive this functionality.

John Catch

My company manufactures a meter interface device (the EtherMeter) that converts flow and totalization from many gas meters into Modbus and Rockwell comm protocols.

For your Quantum PLC, you can get the readings using Modbus/TCP; and if you ever need to link the meter with an Allen Bradley PLC (for example, your ControlLogix), you can use EtherNet/IP.

I also wrote a blog article that describes how to use the EtherMeter for gas meters: http://scadametrics.com/blog/?p=112

Hope this helps!