100A Handheld Contact Resistance Tester

Product Introduction

Currently, conventional QJ44 double-arm DC bridges are widely used in power systems for measuring contact resistance. However, such bridges operate at test currents only in the milliampere range, making it difficult to detect defects such as reduced conductor cross-sectional area in circuits. When measuring contact resistance in high-voltage switch conductive circuits, the presence of oil films and oxide layers between contacts causes measured values to be several times higher than actual contact resistance, failing to accurately reflect the true resistance value. To address this, the Ministry of Electric Power standard SD301-88 "Acceptance and Preventive Test Procedures for AC 500kV Power Equipment" and the revised "Preventive Test Procedures for Power Equipment" stipulate that the measurement current for circuit breaker and isolator contact resistance must not be less than 100A DC to ensure accurate test results.

This product is designed in accordance with the latest Chinese power industry standard DL/T845.4-2019, integrating high-frequency switching power supply technology with digital circuit technology. It is suitable for measuring the loop resistance of switch control equipment. The test current employs the nationally recommended 100A DC. It directly measures loop resistance at 100A and displays the result digitally. This instrument delivers precise measurements and stable performance, meeting the requirements for on-site high-voltage switch maintenance by power and supply departments, as well as loop resistance testing at high-voltage switch manufacturers.

Product Parameter (specification)

Measurement Range	1 to 1999 μΩ
Resolution	1 μΩ
Test Current	DC 100 A
Measurement Accuracy	0.5% ± 1 digit
Display Method
Current	3½-digit LED display
Resistance	3½-digit LED display
Power Supply	AC 220 V ±10%, 50 Hz
Operating Environment	Temperature
-10°C to 40°C Humidity	≤80% RH
Dimensions	390 × 300 × 150 mm³
Weight	6 kg (excluding accessories)

Product feature and application

(1) High Current: Utilizing the latest power supply technology, it delivers sustained high-current output over extended periods, overcoming the limitations of pulse-type power supplies with their transient current spikes. This effectively breaks through the oxide film on switch contacts, yielding reliable test results.

(2) Strong Anti-Interference Capability: Even under severe interference conditions, the final digit on the LCD display remains stable within ±1 digit range, ensuring consistent readings with excellent repeatability.

(3) Extended Service Life: Incorporates high-precision resistors to minimize environmental temperature effects on measurements. Military-grade connectors enhance vibration resistance.

(4) Portable Design: Compact size and lightweight construction.

Prodection details

This device may be used to measure contact resistance (loop resistance) in high-voltage switches with great accuracy. It can also be used in other situations where high-current, micro-resistance measurement is needed.

Company Qualifications

FAQ

1)What testing principle does the MEHL-W100A Loop Resistance Tester employ? How does it operate specifically?

Answer: This instrument utilizes the current-voltage method (also known as the four-wire method) testing principle. The specific operation process is as follows: A current source supplies current to the resistance under test (Rx) through the "I+" and "I-" ports, with the current magnitude read via an ammeter; Simultaneously, the voltage drop across Rx is measured via the "V+, V-" ports and read by the voltmeter; Finally, the resistance value of the measured resistor is calculated using the measured current I and voltage V.

2)What are the key requirements for wiring when using the MEHL-W100A Loop Resistance Tester?

Answer: Key wiring requirements include: 1. Wiring must follow the four-terminal method: current clamps attach to the outer side of the test specimen, voltage clamps to the inner side, and current and voltage must share the same polarity; 2. Connections between the instrument panel and test leads must be securely tightened to prevent loosening; 3. Ensure the instrument is properly grounded before wiring, and never test the loop resistance of energized circuits; 4. Current leads must not be replaced by the user.

3)What advantages does the MEHL-W100A Loop Resistance Tester offer over the traditional QJ44 dual-arm DC bridge?

Answer: Compared to the traditional QJ44 dual-arm DC bridge, its main advantages are: 1. Higher test current (DC 100A) effectively breaks through switch contact oxide layers, preventing overestimated readings and accurately reflecting contact resistance values in compliance with relevant Ministry of Power standards; 2. Superior interference resistance ensures stable readings and excellent repeatability even in highly disturbed environments; 3. Extended service life: High-precision resistors eliminate temperature-induced measurement variations, while military-grade connectors enhance vibration resistance; 4. Compact size and lightweight design facilitate portability, making it ideal for field testing scenarios.

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