The four-wire method uses a pair of wires as the current output wire, and the other pair of wires introduces the voltage drop on the measured resistance into a multimeter for measurement. Because the current of the voltage wire is very small, the measured resistance value is closer to the actual value. Compared with the wire method, the four wire method does not use a bridge, but only uses a constant current source for transmission, measures the voltage, and finally calculates the resistance value, and feeds the current back to the two terminals of the circuit. There are two terminals on the voltage measurement circuit. There are a total of four terminals, so it is called "four-wire measurement". The measurement accuracy of the four-wire method is relatively high.

The characteristic of the four-wire method of the DC resistance tester is that the power supply circuit and the measuring circuit are separated. The panel consists of two current terminals and two voltage terminals. The resistance of the measuring circuit is almost negligible, almost close to itself, so it can Measure micro-ohm resistance. However, due to the limited current, the DC resistance tester is usually used in the measurement range of 0-2000Ω. In addition, the four-wire method also uses the measurement principle of the loop resistance tester.

DC resistance is widely used in power systems, but is mainly used to measure the coil resistance of inductive loads. For example, the DC resistance of the transformer coil, the DC resistance of the transformer, the coil resistance of the reactor, etc.