When the measured object is connected to the power supply, it should be taken out of the running state before the measurement, cut off the power supply, and the measured object is not allowed to be charged for the test. Otherwise, not only the insulation resistance cannot be measured, but the megohmmeter will be damaged and the human body will be damaged. Electric shock and other accidents. For the tested object after disconnecting the power supply, it should be fully discharged between the tested points or short-circuit to the ground after the electrical test, especially the equipment containing capacitors and equipment with large capacitance, such as large motors, long cables , Large-capacity transformers, etc., the discharge time needs to be longer, generally two to three minutes, and if necessary, the measured point and related parts of the measured object should be short-circuited for a period of time and then opened. Wait for a period of time. Short-circuit, repeat this several times, until it is confirmed that there is no residual charge, then the measurement can be performed. Although some measured objects are not directly related to the power supply, if there are high-voltage, high-current conductors or radiating electromagnetic field signals inside or near it, such influencing factors must also be eliminated. In short, the insulation resistance can be measured only when the object under test is not charged and cannot be induced by other power sources, so as to ensure the safety of personnel and instruments and the accuracy of the test results.

In order to ensure the accuracy of the test results, the measurement part of the measured object must be cleaned. For example, the vicinity of the measured point and the surface of the measured object should be wiped clean, and there should be no dirt or moisture, so as not to affect the measurement due to its leakage factor. Accuracy. For the test points connected to the test line on the test object, it is also required to be clean and clean. All dust, oil and rust should be eliminated, contact resistance should be reduced, and the reliability of electrical contact should be ensured.