In a current loop, the output voltage from a sensor is first converted to a proportional current, in which 4mA normally represents the sensor's zero-level output and 20mA represents the full-scale output. A receiver at the remote end converts the 4-20mA current back to a voltage, which can be further processed by a computer or display module. The typical 4-20mA current-loop circuit consists of four elements: a sensor/transducer, a voltage-to-current converter, a loop power supply, and a receiver/monitor. In loop-powered applications, the sensor drives the voltage to- current converter, and the other three elements are connected in series to form a closed loop. This is the figure of the operation diagram.
