Signals and sensors

4–20 mA scaling calculator

Convert a 4–20 mA current to an engineering value, reverse the calculation and check optional loop-voltage headroom.

Calculate

Signal and engineering range
mA
For display only, for example bar, °C or l/s.
Optional loop-voltage checkOptional

Complete all four values to check headroom at the calculated current.

V
V
Ω
Ω

Worked example

Engineering value

50 %

Loop current
12 mA
Position across the 4–20 mA span
50 %

The signal is within the 4–20 mA measuring span.

Method and assumptions

Formula

Value = low + (mA − 4) × (high − low) ÷ 16

This is a linear mapping. Confirm the transmitter transfer function and any fault-current convention in its datasheet.

Limits of this result

  • A loop-headroom check requires all four optional values. It applies only at the calculated current and does not prove operation at maximum or fault current.
  • Verify transmitter and receiver voltage limits, maximum loop voltage, isolation, wiring polarity and the device-specific fault-current convention.

Technical sources

  1. 4–20 mA Current Loop FundamentalsNational Instruments · updated 2025-02-03

Put the value to work

Read the related engineering guidance, or carry this task into System Builder to identify the signal path and EpiSensor products.

Continue in System Builder Read: What Is SCADA?

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