4–20 mA table: current vs percentage of range (and 1–5 V)
4 to 20 mA current for every 5% of range, voltage across a 250 Ω resistor (1 to 5 V) and percentage for every mA, with the NAMUR NE 43 failure limits.
In a 4–20 mA signal, 4 mA is 0% of the configured range (LRV) and 20 mA is 100% (URV). The relationship is linear: each 1% of range is worth 0.16 mA. Many input cards read the current across a 250 Ω resistor, giving 1 to 5 V.
| % of range | mA | V across 250 Ω |
|---|---|---|
| 0 | 4.00 | 1.000 |
| 5 | 4.80 | 1.200 |
| 10 | 5.60 | 1.400 |
| 15 | 6.40 | 1.600 |
| 20 | 7.20 | 1.800 |
| 25 | 8.00 | 2.000 |
| 30 | 8.80 | 2.200 |
| 35 | 9.60 | 2.400 |
| 40 | 10.40 | 2.600 |
| 45 | 11.20 | 2.800 |
| 50 | 12.00 | 3.000 |
| 55 | 12.80 | 3.200 |
| 60 | 13.60 | 3.400 |
| 65 | 14.40 | 3.600 |
| 70 | 15.20 | 3.800 |
| 75 | 16.00 | 4.000 |
| 80 | 16.80 | 4.200 |
| 85 | 17.60 | 4.400 |
| 90 | 18.40 | 4.600 |
| 95 | 19.20 | 4.800 |
| 100 | 20.00 | 5.000 |
| mA | % of range |
|---|---|
| 4 | 0.00 |
| 5 | 6.25 |
| 6 | 12.50 |
| 7 | 18.75 |
| 8 | 25.00 |
| 9 | 31.25 |
| 10 | 37.50 |
| 11 | 43.75 |
| 12 | 50.00 |
| 13 | 56.25 |
| 14 | 62.50 |
| 15 | 68.75 |
| 16 | 75.00 |
| 17 | 81.25 |
| 18 | 87.50 |
| 19 | 93.75 |
| 20 | 100.00 |
Outside 4 to 20 mA
Below 4 mA or above 20 mA the signal has left the range: it may be saturation, a transmitter failure or a loop problem. Transmitters configured for NAMUR NE 43 measure from 3.8 to 20.5 mA and signal a failure with 3.6 mA or less, or 21 mA or more. Zero or almost zero means an open loop or no supply.
The percentages apply to any range. To get to the process unit (bar, °C, m³/h), use the endpoints configured in the instrument.
Values calculated from the reference functions; they do not replace measurement or a calibration certificate.