Signal Loop Wiring Calculator
Loop resistance · voltage budget · max cable length
Loop
Wire
Series Devices (burden)
Add each device in the loop with its burden resistance (Ω). Sense resistors, PLC AI cards, indicators and recorders all add up in series.
Result
Enter your supply, wiring and series devices to get the total loop resistance, total voltage drop, a Pass/Fail voltage-budget check with the exact margin, or switch to reverse mode to find the maximum cable length the loop can support
The voltage budget is checked at the worst case — maximum loop current, which is 20 mA for a 4-20mA loop — because that is when the voltage drop across the wiring and burden is greatest. Total resistance is the round-trip wire resistance plus every series burden; the transmitter itself also needs a minimum operating voltage, so include that as the minimum-voltage figure or as a burden as appropriate. Built-in gauge resistances are typical copper values at about 20 °C, and real resistance rises with temperature, so raise the value for hot runs. HART communication needs at least 230–250 Ω of loop resistance to work, which is a separate consideration from this voltage check. Always confirm against the device datasheets and your cable specification.