Insulation resistance meter circuit diagram

The insulation resistance meter (also known as the megohmmeter) measures the insulation resistance value under the rated voltage. Although the multimeter can also measure the
insulation resistance value of several thousand ohms, the insulation resistance value it measures is only It can be used as a reference, because the battery voltage used by the multimeter is low, and the insulating material is not easy to breakdown when the voltage is low. Generally , the electrical equipment
being measured must be connected to a higher working voltage, so only insulation can be used. Use a resistance meter to measure . It is also generally stipulated that when measuring the insulation resistance of electrical equipment with a rated voltage above 500v, an iooo-2soov insulation resistance meter must be used. To measure electrical equipment with voltages below 500v, it is appropriate to use a 500v insulation resistance meter.     The measurement method of the insulation resistance meter is as follows.     1) Before measurement, the insulation resistance meter should be subjected to an open circuit test first and then a short circuit test. The needle of the meter should point to ~ (infinity) l during the open circuit test and swing to "o" during the short circuit test. This indicates that the insulation resistance meter is in normal working condition and can measure electrical equipment.   2) Select the voltage level of the insulation resistance meter according to the rated voltage of the electrical equipment under test : generally to measure the insulation of electrical equipment below 50V, a 250V insulation resistance meter can be used; to measure the insulation of electrical equipment between 50 and 380V. A 500v insulation resistance meter can be used. When measuring electrical equipment below 500V, the insulation resistance meter should be selected with a reading starting from zero, otherwise it will be difficult to measure . Because under normal circumstances, when there is no fault in the electrical equipment, its insulation resistance is o. When it is above 5 Mfl, who can energize the electrical equipment for use. If an insulation resistance meter with a reading starting from 1Mfl is selected, the insulation resistance less than 1MC1 cannot be read.     When selecting external wires for the insulation resistance meter, single multi-stranded actinium wires should be used instead of double-stranded insulated wires, and the insulation strength should be above 500v . Otherwise it will affect the accuracy of the measurement.     3) When measuring the insulation resistance of electrical equipment, the power supply of the equipment must be disconnected first. If it is a capacitor or a long cable line, it should be measured after discharge.     4) When using the insulation resistance meter, it must be kept away from strong magnetic fields and placed flat. When shaking the megohmmeter, avoid vibration to the meter. 5) The surface of the electrical equipment     under test should be cleaned before measurement to avoid inaccurate measurement results.     6) When it comes to the insulation resistance of a guillotium capacitor, the withstand voltage of the capacitor must be greater than the voltage value output by the insulation resistance meter. After measuring the capacitance, you should first remove the insulation resistance meter wire and then stop shaking the handle to prevent the charged capacitor from discharging into the insulation resistance meter and damaging the meter. The measured capacitance needs to be discharged using a resistor.