Sparky tools
4-20 mA Signal Scaler
What process value is 12 mA, or what current is 50 kPa? Linear and square root.
Data: No standard tables used. Linear and square-root scaling only. About standard editions
For reference only. Always verify instrument scaling against the manufacturer data sheet and site calibration records.
Signal Scaler Inputs
Linear scaling: standard for pressure, temperature, level
The process variable unit label (display only)
mA
Calibration Reference
5-point table for linear scaling: 0 to 100 kPa
| % Range | Signal (mA) | PV (kPa) |
|---|---|---|
| 0% | 4.000 | 0.000 |
| 25% | 8.000 | 25.000 |
| 50% | 12.000 | 50.000 |
| 75% | 16.000 | 75.000 |
| 100% | 20.000 | 100.000 |
About 4-20 mA Signals
- 4 mA = 0% of range (zero / LRV). A live zero allows fault detection: a true 0 mA indicates a broken loop.
- 20 mA = 100% of range (span / URV).
- Square root extraction is used with DP (differential pressure) flow transmitters because flow rate is proportional to the square root of differential pressure.
- NAMUR NE 43 defines signal levels for fault indication: <3.6 mA and >21.0 mA are typically used for diagnostics.
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