4 to 20 mA and 0 to 10 V loop scaling calculator
You need to turn a loop current into engineering units and ADC counts, and catch a broken wire before it shows up as a fake zero. Sense resistor voltage, ADC counts, engineering units, resolution per count, and wire-break detection to NAMUR NE 43.
Open the calculator in EM·LINKBelow is a worked example. The working calculator runs free in EM·LINK.
Worked example
Example inputs
Example result
Inside the NE 43 measuring range of 3.8 to 20.5 mA. No fault.
| Quantity | Value |
|---|---|
| Sense voltage | 1.890 V |
| ADC counts | 2345 |
| Counts at 4 mA | 745 |
| Counts at 20 mA | 3723 |
| Resolution | 0.0034 bar per count |
| Wire-break limit (3.6 mA) | 670 counts |
A 21 mA fault reads 3.150 V (3909 counts), still under the 3.3 V reference.
Calculations run in your browser. Nothing is sent to us.
The working calculator is 4–20 mA / 0–10 V Loop Scaling in EM·LINK, our free browser tool. The button opens it directly.
How to read the result
Most scaling mistakes come from the sense resistor. A 250 ohm resistor puts 20 mA at 5 V, which clips a 3.3 V ADC. On a 3.3 V reference, 150 ohm keeps the whole NAMUR NE 43 range, including the 21 mA fault level, inside the ADC.
NE 43 bands tell you whether a low reading is a real low process value or a wire break.
How this is calculated
The loop current flows through the sense resistor. The ADC converts that voltage to counts, and the 4 to 20 mA span maps linearly onto the engineering range.
The full derivation, step by step, is in the EM·LINK documentation.
Calculated per NAMUR NE 43. These tools are an engineering aid, not a certification.
Next step
Logging these sensors across the plant? Embedos Edge takes analog and digital I/O.
Common questions
What sense resistor should I use with a 3.3 V ADC?
150 ohm. It puts 20 mA at 3.0 V and the 21 mA fault level at 3.15 V, so faults are still visible. 165 ohm would clip faults at 3.3 V. The classic 250 ohm is meant for 5 V systems.
What current means a broken wire on a 4 to 20 mA loop?
Per NAMUR NE 43, below 3.6 mA is treated as a wire break or under-range fault.
Does it handle 0 to 10 V inputs?
Yes, the same scaling works for voltage inputs.
Related tools
- RTD PT100 and PT1000, when the transmitter in the loop is an RTD head transmitter you want to check.
- ADC resolution and noise, to see how many of those counts are real and how many are noise.
- Thermocouple type K and J, for direct thermocouple inputs without a transmitter.