The 4-20 mA current loop is the de-facto industrial standard for analog signal transmission since the 1970s. This calculator handles the bidirectional conversion between the current value (mA) and the process variable (PV) for any range.

NAMUR NE 43 defines the diagnostic bands :

• < 3.6 mA : sensor failure or wire break
• 3.6 – 4 mA : underrange (saturation low)
• 4 – 20 mA : normal operating range
• 20 – 21 mA : overrange (saturation high)
• > 21 mA : sensor failure (overcurrent)

A modern transmitter signals diagnostic faults explicitly via these out-of-range values rather than failing silently inside the normal band.