Methods for Testing Fixed Capacitors
Release Date:
2023-02-22
1. Testing small capacitors below 10 pF: Because fixed capacitors below 10 pF have such a small capacitance, using a multimeter to measure them can only provide a qualitative assessment of whether there is leakage, an internal short circuit, or dielectric breakdown. When measuring, select the R×10k range on the multimeter and connect the two test leads arbitrarily to the capacitor’s two terminals; the resistance reading should remain high throughout. If the measured resistance (indicated by the needle swinging to the right) reads zero, it means the capacitor is damaged due to leakage or internal breakdown.
1. Testing small capacitors below 10 pF: Because fixed capacitors below 10 pF have such a small capacitance, using a multimeter to measure them can only provide a qualitative assessment of whether there is leakage, internal short circuit, or breakdown. During measurement, select the R×10k range on the multimeter and connect the two test leads arbitrarily to the capacitor’s two terminals; the resistance reading should remain high throughout. If the measured resistance (indicated by the needle swinging to the right) reads zero, it means the capacitor is damaged due to leakage or internal breakdown.
2. Testing fixed capacitors ranging from 10 pF to 0.01 μF: Determine whether charging occurs, thereby assessing the component’s condition. Set the multimeter to the R×1k range. Both transistors should have a β value of at least 100 and low leakage current; silicon transistors such as the 3DG6 can be used to form a composite transistor. Connect the multimeter’s red and black leads respectively to the emitter (e) and collector (c) of the composite transistor. Due to the amplifying effect of the composite transistor, the charging and discharging process of the capacitor under test is amplified, increasing the deflection of the multimeter pointer and making it easier to observe.
It should be noted that during testing, especially when measuring capacitors with relatively small capacitance, the leads of the capacitor under test must be repeatedly swapped between terminals A and B in order to clearly observe the deflection of the multimeter pointer. For fixed capacitors with a rating of 0.001 μF or greater, the R×10k range on the multimeter can be used to directly determine whether the capacitor is undergoing a charging process and whether there is an internal short circuit or leakage; furthermore, the magnitude of the pointer’s rightward deflection can be used to estimate the capacitor’s capacitance.
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