Why 4-20mA used in Instrumentation?

Any process parameter such as Temperature, Pressure, Flow, Density is sensed, measured by a sensor and is converted to an electrical signal in the form of voltage. The voltage from the sensor is sent to the transmitter to convert in a standard form of the current output signal.
1) A major reason is that the loop current does not vary with long field wiring, if the voltage developed in the loop, called the Compliance Voltage, can sustain the maximum loop current.
2)Another benefit is that the current loop has a low impedance and is not particularly susceptible to noise or EMI at large. For analog sensor data transmission, a 4-20 mA current loop is a very common method to convey the sensor data acquired.
3) A third advantage is a live-zero feature of the loop (the 4mA low limit), which makes the loop self-diagnostic if there is a break or bad connection in the loop or a loop power supply failure.
#4-20mA, #CurrentLoop, #AnalogtoDigital,

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