Testing Small Capacitors (Below 10pF): Since the capacitance of fixed capacitors below 10pF is extremely low, using a multimeter for measurement allows only for a qualitative assessment-specifically, checking for leakage, internal short circuits, or dielectric breakdown. To perform this test, select the R×10k range on the multimeter; connect the two test probes to the capacitor's two leads (in either order). The measured resistance value should be infinite. If a finite resistance value is detected (indicated by the pointer deflecting to the right), it signifies that the capacitor is damaged by leakage or has suffered an internal breakdown.
Testing Fixed Capacitors (10pF to 0.01μF): The condition of these capacitors is determined by observing whether a charging phenomenon occurs. For this test, set the multimeter to the R×1k range. This method utilizes a compound transistor configuration; the two transistors used should each have a current gain (β value) of 100 or higher and exhibit low leakage current. Silicon transistors-such as the 3DG6 model-are suitable for constructing this compound pair. The multimeter's red and black probes are connected to the compound transistor's emitter (e) and collector (c), respectively. Thanks to the amplifying effect of the compound transistor, the charging and discharging process of the capacitor under test is amplified, resulting in a larger deflection of the multimeter's pointer and making the observation process much easier.
Important Note: During the testing procedure-particularly when measuring capacitors of smaller capacitance-it is necessary to repeatedly reverse the connections of the capacitor's leads against points A and B in order to clearly observe the deflection of the multimeter's pointer. For fixed capacitors with a capacitance of 0.01μF or higher, the multimeter's R×10k range can be used directly to check for the presence of a charging process, as well as for internal short circuits or leakage. Furthermore, by observing the magnitude of the pointer's deflection to the right, one can estimate the approximate capacitance value of the capacitor.