(1) The experience certificate of the electroscope is excellent. The neon tube does not emit light when the device is inspected, which does not mean that the device has no electricity. If the AC voltage is lower than 50V and the DC voltage is lower than 90V, the electroscope does not emit light. Electric shock may still occur when the human body touches the device, because the safe voltage should be lower than 36V (communication).
(2) When a person stands on the insulating pad and checks the 220V AC voltage with an electroscope, the neon tube glows; but when a person stands on the ground with excellent insulation and uses an electroscope to check the DC voltage higher than the ignition voltage, the neon tube does not emit light. If one end of the DC power supply is grounded, the neon tube glows.
(3) When using an electroscope to check an excellent metal case that is not grounded (connected to zero), sometimes the neon tube will also emit weak light. This is because the normal insulation resistance of low-voltage electrical equipment is less than 1MΩ, and there is a large scattered capacitance between the shell of some equipment and the conductor, while the current limiting resistance of the electroscope is 1~3MΩ, and the leakage current passes through the insulation resistance and the scattered capacitance. , the current limiting resistor and the human body to the ground, the voltage added to the neon tube exceeds its ignition voltage, so the electroscope emits light. Because the leakage current is microampere level, it is harmless to human body. Will not constitute an electric shock incident. However, if the neon tube is brighter, it may be due to poor insulation of the equipment, serious leakage, and risk of electric shock. At this time, use a megohmmeter or a multimeter to check the insulation status of the equipment, and it must not be numb.
