Electrical & Electronics
4–20 mA Signal Scaling Calculator
Convert loop current to engineering units or calculate current from a measured value.
Your inputs
Your results
- Value
- —
- Current
- —
- Percentage of span
- —
| Current · mA | Value |
|---|
—Map loop current to engineering readings
Convert a linear current-loop signal to a measurement or calculate the current for a desired reading. Increasing and descending scales are supported. The tool performs arithmetic mapping; it does not read hardware or calibrate a sensor.
Step by step
- Choose conversion from current or from the engineering reading.
- Enter the readings assigned to the lower and upper current endpoints, then choose a unit label.
- Enter the measured current or desired reading. Review the result, span percentage and range warning.
Settings and limits
- Scale endpoints
- Endpoints must differ. A descending engineering scale is valid; the upper-current endpoint can represent a lower reading.
- Out-of-range values
- The calculation extrapolates beyond the entered span and flags the result. It does not clamp values or diagnose a fault.
- Unit label
- The unit labels the engineering result. Changing it does not convert the endpoint numbers.
Worked example
The first example maps the midpoint current to the midpoint reading. Compare it with the reference table shown by the tool.
Example input
x4 = −50 °C; x20 = 150 °C; I = 12 mA
x4 = 100; x20 = 0; I = 8 mA| x4 | x20 | I | x | % |
|---|---|---|---|---|
| −50 °C | 150 °C | 12 mA | 50 °C | 50% |
| 100 | 0 | 8 mA | 75 | 25% |
The second example reverses the engineering scale. Higher current then represents a lower reading.
Questions and troubleshooting
Why is the percentage negative?
The input lies below the lower-current endpoint. Percentages outside the span indicate extrapolation.
Does this validate sensor accuracy?
No. Verify calibration, measurement uncertainty, wiring and loop supply conditions separately.
Can I use it for a nonlinear sensor?
Only after applying the required linearisation elsewhere. This mapping assumes a straight-line relationship.