4-20mA Signal Converter
Convert engineering range values to a 4-20mA analog signal loop current and vice-versa, ideal for instrumentation loop tests, transmitter calibration, and commissioning of HART field devices.
Range value → 4-20mA
4-20mA → Range value
Formulas
Current (mA) = 4 + (value − range min) / (range max − range min) × 16
Value = range min + (current (mA) − 4) / 16 × (range max − range min)
About the 4-20mA analog signal
The 4-20mA current loop is the industry-standard analog signal for industrial process control and automation. A 4mA reading represents the live zero (0%) of the transmitter range, while 20mA represents full scale (100%). This converter helps technicians and engineers during loop tests and loop calibration: simulate a process value to verify the current reading expected at the PLC, DCS, or SCADA input card, or read a loop current from a multimeter or calibrator and translate it back to the engineering range.
It is also useful when scaling HART field devices such as pressure, temperature, level, and flow transmitters: check the PV (primary variable) scaling against the mA signal, verify over-range and under-range conditions, and validate sensor ranges before commissioning. Readings below 4mA typically indicate a broken wire or faulty transmitter, while readings above 20mA point to an over-range condition or saturation fault.