How to test high resistance? Detailed explanation of practical methods and techniques for high resistance testing

Electronics, electrical and materials fields, highresistanceMeasurement is an important part of ensuring equipment performance and safety. High resistance usually refers to materials or components with very high resistance values, which may reach the megohm level or even higher. Accurate testing of high resistance is important for judging insulation performance, material quality and circuit safety. This article will systematically introduce the basic concepts, common methods and precautions of high resistance testing to help readers master the core skills of high resistance testing.

High resistance generally refers to a resistor with a resistance greater than 1 megaohm (MΩ). Due to the extremely high resistance value, it is difficult to accurately measure the resistance range of a conventional multimeter, and the test process is easily affected by environmental humidity, temperature and the internal resistance of the test instrument. Therefore, high resistance testing requires the use of specialized testing equipment and scientific testing methods.

(1) Insulation resistance tester (megohmmeter): This is the most commonly used high resistance testing instrument, which can provide high-voltage DC power supply and measure the resistance of insulating materials.

(2) High resistance meter: specially designed for measuring extremely high resistance values, with high input impedance and high sensitivity.

(3) Bridge method: Use Wheatstone bridge or electrometer bridge to accurately measure high resistance, suitable for laboratory environment.

(1) Preparation: Confirm that the test object is powered off and clean the test surface.

(2) Connect the test instrument: Connect the test leads of the megohmmeter to both ends of the object under test.

(3) Apply test voltage: Select the appropriate test voltage (usually 250V, 500V or 1000V) according to the regulations of the material being tested.

(4) Read data: After maintaining the voltage for a certain period of time, read the resistance value to determine the insulation performance.

Ambient humidity and temperature have a significant impact on high resistance measurements. Excessive humidity will create conductive paths on the material surface, resulting in low measurement values; rising temperature may reduce the material resistance. The test should be carried out in a dry and constant temperature environment, or the results should be temperature corrected.

High resistance measurements are highly susceptible to static interference, causing data fluctuations. When testing, you should wear an anti-static bracelet and use an anti-static pad to avoid static interference from the human body, and ensure that the instrument is well grounded.

The bridge method eliminates the influence of the instrument's own impedance and improves measurement accuracy by balancing the bridge circuit. This method is suitable for precision testing of material resistance in laboratories, but the operation is complicated and is suitable for use by professionals.

(1) Misunderstanding: Use an ordinary multimeter to measure high resistance. Solution: Use a dedicated high resistance meter or megger.

(2) Misunderstanding: Ignoring environmental conditions. Solution: Control ambient humidity and temperature.

(3) Misunderstanding: The test time is too short. Solution: Maintain the test voltage for a certain period of time to stabilize the reading.

高电阻测试完成后，应详细记录测试条件（电压、环境温度、湿度）、测试时间及测量值，便于后续分析和质量追踪。

高电阻的准确测试是保障电子设备和绝缘材料性能的重要环节。通过选择合适的测试仪器，如兆欧表和高阻计，结合规范的测试步骤和良好的测试环境，可以有效提升测量的准确性和可靠性。同时，掌握电桥法等专业测量技术，有助于满足高精度测试需求。避免常见误区，做好数据记录与分析，是实现高电阻测试科学化管理的关键。希望本文的介绍能帮助您更好地理解和掌握高电阻的测试方法。