It is mainly used to detect the contact resistance of equipment such as high-voltage switch circuit breaker busbar connection points



A loop resistance tester (also known as a contact resistance tester or micro-ohmmeter) is a precision instrument specifically designed to measure the resistance at conductor connection points in electrical circuits.

It is mainly used to detect the contact resistance of equipment such as high-voltage switches, circuit breakers, and busbar connection points. By measuring resistance values at the micro-ohm (μΩ) level, it determines whether electrical connections are good and whether there are hidden dangers such as looseness, oxidation, or corrosion.

⚙️ Working Principle

The core working principle of the loop resistance tester is based on Ohm's law (R=U/I) and the four-terminal measurement method (also known as the four-wire method or Kelvin method).

High current injection: The high-frequency switching power supply inside the instrument outputs a constant DC high current (usually 50A, 100A, 200A, or even higher) to the circuit under test.

Precise voltage measurement: While injecting the high current, the instrument uses independent voltage measurement terminals to precisely measure the voltage drop across the circuit under test.

Automatic resistance calculation: Based on the measured voltage and current values, the internal microprocessor automatically calculates the resistance of the circuit and directly displays it on the screen.

Why are high current and the four-wire method needed?

High current: It can effectively break through the oxide film and oil film on the surface of switch contacts, thereby measuring the true metal contact resistance and avoiding falsely high readings caused by the oxide layer.

Four-wire method: By separating the current output terminals (C1, C2) from the voltage measurement terminals (P1, P2), the influence of the test lead's own resistance and contact resistance on the measurement results can be completely eliminated, ensuring the accuracy of micro-ohm level measurements.