Introduction to the Two-wire Transmitter and the 4-20mA Current Loop


In many control loops, we use 2-wire transmitters to convert various process signals representing flow, speed, position, level, temperature, pressure, strain, pH, etc., to 4-20mA DC for the purpose of transmitting the signal over some distance with little or no loss of signal. This paper reviews the operation and advantages of the 4-20mA transmission standard and the use of loop-powered transmitters.

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