DCS, SCADA, Controllers

Ground loops got your process down? Use signal isolators

Acromag advises using signal isolators and splitters to eliminate 4-20 mA errors and ground loops between instruments.

Acromag advises using signal isolators and splitters to eliminate 4-20 mA errors and ground loops between instruments. The primary function of a signal isolator is to eliminate ground loops that may exist between two or more instruments. A traditional application isolates the control room equipment (computers, PLC, DCS etc.) from field devices, which may have different ground potentials. In addition to breaking up ground loops, the isolators protect control room equipment from damaging transient spikes and noise generated in the field, the company says. Some isolators can produce two identical outputs for routing to different instruments. Acromag suggests:

– Choose proper and most cost effective isolator by understanding of the application and consideration of future expansion requirements.
– Consider various isolator models to cover various system configurations.
– Ask for help, if needed, to decide among two-, three-, or four-wire electrical connections. Will the isolator operate from ac, dc, or loop power? Do you need an input, output, or 3-way (input, output, power) isolators?

www.acromag.com/sites/default/files/Eliminate%20Ground%20Loops%202010_P2.pdf
Also see from Control Engineering :
– Tutorial: Running down interference to improve device performance ;

– Ground Loops ; and
– Process control channel .