DC Resistance Tester is a core instrument in preventive and commissioning tests of power equipment, mainly used to measure the DC resistance of inductive loads such as transformer windings, generator stator/rotor windings, transformer coils, reactors, cable joints, and switch contacts. Its core purposes are: to check the integrity of conductive circuits (such as broken wires, poor contact), verify inter-turn short circuits in windings, evaluate the contact condition of tap changers, and calculate load losses. In the technological context of 2026, this equipment has fully entered the era of "high-speed, intelligent, multi-channel integration," completely solving the pain points of traditional testing such as "slow charging, difficult discharging, and messy data." 1. Core Working Principle and Challenges Principle: It adopts the four-terminal method (Kelvin connection), injecting a stable DC current into the test object through a constant current source (