How to Convert 4–20 mA to Engineering Units: Formula & Examples
In industrial instrumentation, a 4–20 mA signal is useful only when the receiving system can translate the measured current into a meaningful process value. A transmitter may send 12 mA, but an operator usually needs to see a pressure, temperature, flow rate, level or percentage—not just a current value. This conversion is called signal scaling . It is used in PLCs, DCSs, remote I/O systems, panel meters and other control-system devices. In this practical guide, we will learn the 4–20 mA scaling formula, understand why 4 mA represents the lower range value, calculate real industrial examples, and see how an analog input value is converted into engineering units. Scope of this article: The main formula applies to a transmitter whose 4–20 mA output is configured as a linear representation of the measured variable. It assumes that the configured lower range value (LRV) and upper range value (URV) are known. Square-root extraction, custom characterisation, digital communicat...