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Loop Cable Voltage Drop

Copper pair drop by gauge and length.

Inputs

Cable and current

Loop current, design at 20 mA plus alarms.

One-way cable metres, doubled inside.

Copper section; 0.5 is 20 AWG, 0.75 is 18 AWG.

Copper resistance rises 0.393 % per C above 20 C.

Result

Drop (V)
0.688
Loop resistance (ohm)
34.40
Calculation details
Cable loss (mW)
13.76

Verify

Check before relying.

Copper length is a voltage.

  • One-way metres doubled for the pair
  • Conductor section from the cable print
  • Terminals add ~0.1 V each when corroded
This calculator is a first-pass screening tool. Verify nameplate data, wiring, module configuration, and calibrator readings before acting.

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