The insulation resistance of all electrical devices and equipment must comply with the requirements of relevant norms and standards to ensure safety during on-site operation. Whether it is electrical cables, sectional protection equipment, or motors, generators, etc., the electrical conductor parts must be isolated using materials with high insulation resistance to prevent current from flowing out.
Over time, the quality of the insulating material will deteriorate due to the influence of the environment where the equipment is located, working conditions, or other external forces. This reduces the resistivity of the insulating material, thereby increasing the leakage current, which may lead to serious accidents that threaten personal or property safety, and may cause factory production to stop and result in economic losses.
The insulation resistance tester is suitable for measuring the resistance values of various insulating materials, as well as the insulation resistance of transformers, motors, cables, and electrical equipment. It ensures that these devices, appliances, and circuits operate in a normal state, preventing accidents such as electric shock injuries and equipment damage.
For test samples with significant capacitive loads, a suitable voltage level, a sufficiently large output short-circuit current, a wide range of insulation value measurement, and an insulation resistance tester that can automatically discharge the tested item are generally selected. Otherwise, the resistance value will be affected to a large extent, causing a significant error in the absorption ratio test results. For test sites with strong interference, a pointer-type insulation resistance tester should be selected because a digital display one has larger fluctuations in measurement data, making it impossible to confirm the true resistance value. The pointer-type megohmmeter itself is relatively resistant to strong magnetic field interference (due to the damping effect of the mechanical dial). Even if there is an impact, the pointer display only shows a slight oscillation, and the indication range is also very intuitive.
For situations where there is less interference and precise measurement of insulation resistance values is required, a digital display should be selected because digital displays are intuitive and have higher accuracy. For scenarios where the measurement of large-capacity test samples such as absorption ratio and polarization index is needed, an intelligent insulation resistance tester capable of automatically measuring the absorption ratio and polarization index should be chosen.
The insulation resistance tester can be used to measure the resistance values of various insulating materials as well as the insulation resistance of transformers, motors, cables, and electrical equipment. During on-site tests, some common problems may arise.
What does the magnitude of the output short-circuit current represent?
Longer cables, motors with more windings, transformers, etc. belong to capacitive loads. When measuring the resistance of such objects, the magnitude of the short-circuit current output can reflect the internal resistance of the high-voltage output source inside the megohmmeter.
Why use the “G” terminal of the instrument to measure higher resistance values?
The “G” terminal (shielding terminal) of the instrument is designed to eliminate the influence of moisture and dirt in the testing environment on the measurement results. When measuring high resistance values, if the results are found to be unstable, using the G terminal can help reduce errors.
Apart from measuring the resistance value, why is the absorption ratio and the polarization index also measured?
In the insulation test, the insulation resistance value at a certain moment cannot fully reflect the quality of the insulation performance of the test sample. Firstly, for the same insulation material, when the volume is large, the insulation resistance is small; when the volume is small, the insulation resistance is large. Secondly, after adding high voltage, insulation materials all have processes of charge absorption ratio (DAR) and polarization (PI).
Why can a relatively high direct current voltage be generated?
According to the principle of DC conversion, the insulation resistance tester powered by several batteries is processed through a boosting circuit. The lower supply voltage is raised to a higher output DC voltage. Although the generated high voltage is relatively high, the output power is relatively small.
Post time: Mar-23-2026