DC Resistance Tester is a specialized instrument used in power testing to measure the DC resistance of inductive loads such as transformer windings, mutual inductors, reactors, and motor windings. It is one of the most effective means to detect defects such as poor coil welding quality, inter-turn short circuits, poor contact of tap changers, and broken conductors. Combining the latest technical standards and market product features from 2025-2026, here is the core analysis of this equipment: 1. Core Functions and Testing Principles Main Uses: Transformer Winding Testing: Detect three-phase resistance unbalance rate (usually required to be ≤2% or 4%), identifying inter-turn short circuits or loose lead connections. On-Load Tap Changer (OLTC) Inspection: Quickly capture the transition resistance waveform during switching to determine contact erosion or sticking. Loop Resistance Measurement: Although micro-ohmmeters are more common, some high-precision DC resistance testers can also be used for circuit breaker conductive loop testing. Technical Principle: Utilizes the four-terminal method (Kelvin connection) to eliminate the influence of lead resistance, uses a constant current source to output stable DC current, and employs high-precision AD conversion to collect voltage drop, thereby calculating the resistance value (