Eliminating 4-20mA Errors

Eliminating 4-20mA Errors and Extending Loops with Signal Isolators and Splitters


The primary function of a signal isolator is to eliminate ground loops that may exist between two or more instruments. A classical 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.

Signal splitters take a 4-20mA signal and provide two identical isolated 4-20mA outputs for routing to different instruments, such as a recorder and a controller. Each channel operates independently and is isolated from the other to prevent interaction.

Choosing the proper and most cost-effective isolator requires an understanding of the application and consideration of future expansion requirements. This is why Acromag offers dozens of isolator and splitter models to cover all the possible system configurations. Should you use two-, three-, or four-wire electrical connections? Will the isolator operate off AC, DC, or loop power? Do you need input, output, or 3-way (input, output, power) isolators? Then there are the mounting, calibration, and load resistance issues. For help selecting the best unit for your situation, call us or download our application notes below.
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