Wire gauge and voltage drop calculator
A field transmitter sits at the end of a long cable run and you need to know if the loop still has enough compliance voltage. Loop voltage drop for field wiring with copper temperature correction, plus a 4 to 20 mA compliance-voltage budget.
Open the calculator in EM·LINKBelow is a worked example. The working calculator runs free in EM·LINK.
Worked example
Example inputs
Example result
6.79 V above a 12 V minimum at full scale, 20 mA.
| Quantity | Value |
|---|---|
| Conductor diameter | 0.644 mm |
| Cross-section | 0.326 mm² |
| Resistance per metre | 0.0530 Ω |
| Loop resistance (200 m) | 10.59 Ω |
| Cable drop at 20 mA | 0.212 V |
| Sense resistor drop | 5.00 V |
At 60 °C the cable drop rises to 0.245 V. This run could reach about 3.3 km before the transmitter falls below 12 V.
Calculations run in your browser. Nothing is sent to us.
The working calculator is Wire Gauge & Voltage Drop in EM·LINK, our free browser tool. The button opens it directly.
How to read the result
Example: 24 V supply, 100 m of AWG 22, 250 ohm sense at 20 mA leaves about 18.8 V at the transmitter.
Most industrial transmitters need at least 12 V, so check margin before pulling cable.
How this is calculated
The AWG number sets the conductor diameter. Copper resistivity is corrected for temperature, and the current flows out and back, so the cable length counts twice.
The full derivation, step by step, is in the EM·LINK documentation.
Calculated per AWG definition (ASTM B258). 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
How much voltage drop on 100 m of AWG 22 at 20 mA?
About 0.21 V at 20 °C for the loop, out and back (about 10.6 ohm of copper).
What compliance voltage does a 4 to 20 mA transmitter need?
Commonly 12 V or more. Check the datasheet.
Does temperature matter?
Yes. Copper resistance rises about 0.39 percent per C.
Related tools
- 4 to 20 mA and 0 to 10 V loop scaling calculator, to scale the loop current once the budget checks out.
- RTD PT100 and PT1000, for the lead-wire error on a 2-wire RTD run.
- ADC resolution and noise, to see what the receiving input can actually resolve.