4–20 mA Scaling Calculator

Convert between loop current and process value for any instrument range.

Direction

Range low (LRV, at 4 mA)

Range high (URV, at 20 mA)

Engineering unit (label)

Loop current (mA)

Process value

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How 4–20 mA scaling works

Industrial transmitters map a measurement range linearly onto a 4–20 mA current loop: 4 mA represents the lower range value (LRV) and 20 mA the upper range value (URV). The conversion is

P V = L R V + (U R V - L R V) \cdot \frac{I - 4}{16}

The live zero at 4 mA lets the receiver detect a broken wire (0 mA) as a fault rather than a valid reading. Per NAMUR NE 43, currents below ≈3.8 mA or above ≈20.5 mA indicate sensor failure.

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