Method for detecting leakage of circuit board and protective measures
Published time: 2019-08-15
Leakage is a current leakage caused by insulation damage or other causes. Leakage occurs when there is a certain potential difference between the electrical enclosure and the mains and the live line for some reason. The best way to detect leakage is to use an electric pen to contact the charged body. If the bubble is bright, it will be extinguished immediately, which proves that the charged body is static; if it is long, it is leaking.
1. Use the on/off file of the multimeter to measure the ground and the part of the circuit. If the meter shows resistance, it is judged not to be insulated.
2, but in fact, if the leakage is measured, you should use a megohmmeter, which is also a shake table. Because the voltage at both ends of the test pen is very low when measuring the multimeter, it generally does not exceed 9v, and it cannot break through the gap leakage. The megohmmeter can reach more than 1000v. Connect the multimeter connector to measure the AC power corresponding to the binding post, then use a pen to measure the zero line or the ground line. The other pen measures the area where you suspect the leakage, and see the number of the universal use. If it is 0, say there is no leakage here, no Voltage! If it is 220 or other voltage display exceeding 36V, it is leaking, which means it is not safe here!
3. Measure the insulation resistance with the multimeter resistance file 200M file, first determine which line is leaking, or which two lines are shorted.
1 The easiest way is to exchange the position of the live and neutral wires (such as turning the two-phase plug 180 degrees into the socket), this method is generally very effective. Because some electrical appliances must follow the principle of “left zero right fire”, the leakage of the casing will occur after the insertion. In particular, computers and printers must strictly follow this principle. I have encountered this situation. After the plug is inserted, the computer mainframe and the printer are powered. The hand does not dare to touch the metal case. The test is done with an electric pen. The bubble is very bright. The voltage measured by the multimeter and the ground reaches 160. After multiple volts, the position of the live and neutral lines is exchanged and the power is not taken.
2 Clean the dust on the board, especially the dust on the power board. Because if there is too much dust, it will conduct electricity (especially when it is wet). When the high voltage and low voltage parts are connected, the outer casing may be charged. In this case, the dust on the circuit board should be cleaned. If the dust after moisture is difficult to remove, clean it with absolute alcohol. After it is finished, blow it off with a hair dryer to remove moisture.
3 If the above method does not work, then the most effective way is to ground the case. By directing this electricity to the ground, people will not be "electricized."
A leakage protection switch or a leakage protection socket should be installed to prevent the occurrence of serious leakage accidents.
The leakage protector for the purpose of electric shock protection can be installed on small-scale trunk lines. Protect the lines and equipment below. It is also possible to selectively install a leakage protector on the branch or for a single device. The normal leakage current is relatively small, and the rated operating current of the leakage protector can be selected to be smaller, but generally, it is not necessary to pursue a small operating current, and an excessively small operating current is prone to frequent disturbances.
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