DC resistance tester checks whether the winding has inter-turn short circuit



The DC resistance tester, also often called a micro-ohmmeter or transformer DC resistance tester, is an electronic measuring instrument specifically designed for high-precision measurement of low resistance values (typically in the milliohm or even microohm range). It is widely used in power system commissioning tests, preventive tests, and equipment maintenance.

⚡ Core Working Principle

The measurement of the DC resistance tester is based on Ohm's law (R=V/I).

Internally, the instrument outputs a known and stable DC test current to the object under test through a constant current source, while simultaneously measuring the voltage drop across the object with high precision, thereby automatically calculating the resistance value.

To achieve high-precision measurement and eliminate interference, it commonly adopts the following two core technologies:

Four-wire (Kelvin) measurement method: Uses separate current output terminals (C1, C2) and voltage sampling terminals (P1, P2). This method completely eliminates the influence of test lead resistance and contact resistance on the measurement results, ensuring that the true resistance of the measured object is obtained.

Constant current source and automatic arc suppression technology: Provides a stable test current with multiple selectable ranges. For inductive loads such as transformers and motors, the instrument has automatic arc suppression and inductance compensation functions, which can safely absorb the magnetic energy stored in the inductive load after the test, preventing high-voltage back electromotive force from damaging equipment or endangering personnel safety.