What is the insulation resistance testing standard for a multimeter
1, The insulation resistance of the movable part of the high-voltage distribution device shall not be less than 1M Ω, and the insulation resistance of the high-voltage main circuit shall not be less than 250M Ω.
2, For AC motors with insulated stator rated voltage above 1000V, use a 2500V megger to measure. The stator should not be less than 1M Ω and the rotor resistance should not be less than 0.5M Ω. For motors with rated stator voltage below 1000V, use a 1000V megger to measure. The insulation value should not be less than 0.5M Ω. For motors with rated stator voltage below 500V, use a 500V megger to measure. The insulation value should not be less than 0.5M Ω.
3, After repairing the AC motor, measure the insulation resistance of the winding between phases and between phases and ground. For motors below 500V, the insulation resistance after repair shall not be less than 1M Ω, and for motors above 500V, the insulation resistance of the winding after repair shall not be less than 5M Ω.
4, Cable insulation resistance test: The insulation resistance of newly installed and laid cables shall not be less than 50M Ω; The insulation resistance of high-voltage cables during operation shall not be less than 2M Ω; When measuring the insulation resistance of low-voltage cables, the power supply and load side should be disconnected. After the measurement is completed, the three-phase of the cable should be discharged to ground.
What are input resistance and output resistance
1. Input resistance: refers to the equivalent resistance seen from the input end of the amplification circuit.
2.The larger the Ri, the smaller the current that the amplification circuit extracts from the signal source, and the input voltage Ui obtained by the amplification circuit is closer to the signal source voltage Us.
3.However, if the internal resistance Rs of the signal source is constant, in order to increase the input current, Ri should be made smaller.
4.Therefore, the size of the input resistance of the amplification circuit should be designed according to needs.
5. Output resistance: refers to the Thevenin equivalent resistance seen from the output end of the amplifier, which serves as the internal resistance of the load signal source to illustrate the amplifier's ability to carry a load.
6. Output resistance is an important indicator used to balance the impact of an amplifier on the signal source. The larger the output resistance, the smaller the current the amplifier receives from the signal source.
