25-08-2017, 09:32 PM
Signal Conditioning
Signal.ppt (Size: 572.5 KB / Downloads: 94)
4-20 mA Analog electrical transmission standard
Signal is a current loop where 4 mA represents zero percent signal and 20 mA represents the one hundred percent signal.
The "live zero" at 4 mA allows the receiving instrumentation to distinguish between a zero signal and a broken wire or a dead instrument and provides good noise immunity.
The live zero also allows low-power instruments to be directly powered from the loop.