Selectable-Range Current Loop

Abstract:Thisarticleshowsanexampleofimplementinga4-20mAor0-20mAcurrent-loopoutputusingavoltageoutputdigital-to-analogconverter(DAC)andaVtoIconverter.Maxim>AppNotes>A/DandD/ACONVERSION/SAMPLINGCIRCUITSAMPLIFIERANDCOMPARATORCIRCUITSSWITCHESANDMULTIPLEXERSKeywords:4-20mA,0-20mA,currentloop,currentlooptransmission,DAC,V/I,VtoI,converter,digitaltoMay31,2002analogconverterAPPLICATIONNOTE1085Selectable-RangeCurrentLoopAbstract:Thisarticleshowsanexampleofimplementinga4-20mAor0-20mAcurrent-loopoutputusingavoltageoutputdigital-to-analogconverter(DAC)andaVtoIconverter.Current-loopsignals,asopposedtovoltagesignals,arecommonlyusedinindustrialsystemsbecausetheyaremuchlesssubjecttonoiseandrelativelyindifferenttolinelength(becausethecurrentisunaffectedbylineresistance).ThecircuitofFigure1allowsdigitalselectionbetweenthetwostanda