Method of detecting fixed capacitors.

Last Update Time: 2019-11-06 11:05:23

   1. A method for detecting 51-100pF fixed capacitors using a pointer multimeter.

   First, the detection circuit.

   For capacitors between 51-100pF, it is impossible to measure the quality of capacitors by using multimeter directly. If you measure directly, the pointer will not move at all. Three transistor of the same type (such as 3DC201C, etc.) of  a β value greater than 200, can be connected into a multi-composite tube test circuit (the intermediate tube base electrode is connected to the front tube emitter, the rear tube base electrode is connected to the middle tube emitter, and the three-tube collector electrode is connected together). Dial the multimeter to Rx 10k gear, black watch pen to the collector of the composite tube, red watch pen to connect the emitter of the rear tube, between the b and e poles of the front tube, as shown in figure 1.


Second, the detection method.

Pick up the capacitor under test, and then replace the capacitor, two ends  reverse connections. Comparing the deflection of the watch needle between the two times, it should be micro pendulum and return to ∞, indicating that the capacitor is normal; if the watch needle is not moving at all or the resistance value is 0, both of them indicate that there is a problem with the measured capacitor and can no longer be used.


    2. A method for detecting high voltage fixed capacitors between 0.01 μ F and 51pF using a pointer multimeter.

    The high voltage and small capacity electrical appliances between 0.01 μ F and 51pF cannot be measured directly by multimeter. If you measure it, the pointer won't move at all. This kind of capacitor can be checked by adding AC220V power supply measuring capacitor. The specific methods are as follows:

    As shown in figure 1, the capacitor is serially connected between the multimeter, the multimeter is dialed to the measuring AC 250V voltage gear position, and then the meter pen is plugged into one end of the capacitor AC power supply. The pointer should swing. The smaller the capacity, the smaller the wobble. If the watch needle does not move at all, it means that the capacitor is broken and cannot continue to be used. In carrying out the above measurements, attention should be paid to safety.


    3. A method for detecting fixed capacitors above 0.01pF using a pointer multimeter.

    First, the normal measurement law.

    Touch the pins at both ends of the capacitor with the multimeter Rxl0k, and the pointer on the table should swing slightly in the direction of "0"-the larger the capacity value, the greater the amplitude of the wobble, and then restore to ", and then exchange the multimeter pen for position to measure. See if the needle wobbles again. If it conforms to the above law, it indicates that the capacitor measured is good.

    Second, the law of capacitance fault.

   (1). If the watch pin is placed near "0" when the two pins of the capacitor are hit, the capacitor has been broken through.

   (2). If you place it in another position and do not return to the "position, the capacitor has leakage.

   (3). If the pointer does not swing at all, repeatedly change the meter pen to measure do not swing, indicating that the capacitor has been damaged.

   The above three cases show that the capacitor has been damaged and cannot continue to be used.

III. Issues that need to be explained.

If the multimeter does not have Rx 10k gear, it can also be indirectly measured by adding serial DC voltage.


    4. A method for detecting insulation resistance of fixed capacitors using a pointer multimeter.

    The dielectric insulation resistance between the two pins of the non-polar capacitor is measured by using the pointer type high ohmic block, which should be close to ∞. If the measured resistance value is less than 1M0, it indicates that the measured capacitance has obvious leakage or dielectric has been broken down and damaged and cannot continue to be used. 

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