Selectable-Range Current Loop

Abstract: This article shows an example of implementing a 4-20mA or 0-20mA current-loop output using a voltage output digital-to-analog converter (DAC) and a V to I converter.
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Keywords: 4-20mA, 0-20mA, current loop, current loop transmission, DAC, V/I, V to I, converter, digital to May 31, 2002
analog converter

APPLICATION NOTE 1085
Selectable-Range Current
Loop

Abstract: This article shows an example of implementing a 4-20mA or 0-20mA current-loop output using a
voltage output digital-to-analog converter (DAC) and a V to I converter.


Current-loop signals, as opposed to voltage signals, are commonly used in industrial systems because they are
much less subject to noise and relatively indifferent to line length (because the current is unaffected by line
resistance). The circuit of Figure 1 allows digital selection between the two standa