In the illuminating article “What is a Four-wire RTD?” from Instrumentation Tools, the Kelvin or four-wire method emerges as a solution to wire resistance issues in electrical measurement techniques.

Primarily utilized for precise resistance measurements in laboratory settings, the four-wire technique employs four wires to connect the resistance under test, such as an RTD, to the measuring instrument. Two wires convey excitation current to the RTD, while the other two sense voltage drop across the RTD resistor element and transmit the signal to the voltmeter.

Calculation of RTD resistance utilizes Ohm’s Law, dividing the measured voltage displayed by the voltmeter by the regulated current value from the current source.

Diving into the intricacies of four-wire RTD circuits, this analysis highlights the insignificance of wire resistances due to the isolation of voltage drops from the voltmeter. This method ensures precise measurements by minimizing the impact of wire resistance on the accuracy of the readings.

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