How to measure capacitance with an analog multimeter
Detection of fixed capacitors
(1) Detection of fixed capacitors with a capacity above 0.01 pF. Adjust the pointer multimeter to the R×10k ohm range and perform ohm zero adjustment. Then use the red and black test leads of the multimeter to touch the two pins of the capacitor respectively, and observe the multimeter pointer. changes, as shown in Figure 1. If the pointer of the multimeter swings slightly to the right when the test leads are turned on, and then returns to infinity. After changing the test leads, measure again, and the pointer also swings to the right and returns to infinity, then it can be judged that the capacitor is normal; , if the pointer of the multimeter swings to near "0", it can be judged that the capacitor has been broken down or has serious leakage; if the pointer does not return to infinity after swinging when the test lead is turned on, it can be judged that the capacitor is leaking; if the multimeter is used twice If the pointer does not swing, it can be judged that the capacitor is open circuit.
(2) Detection of fixed capacitors with a capacity less than 0.01 pF. When detecting small capacitors below 10 pF, because the capacitance is too small, a multimeter is used to measure it. It can only check whether there is leakage, internal short circuit or breakdown: choose when measuring. Use the R×10k scale of the multimeter. Connect the two test leads to the two pins of the capacitor. The resistance should be infinite. If the measured resistance value is zero, it can be determined that the capacitor is damaged by leakage or internal breakdown.
(3) To detect 10pF~0.01; tF fixed capacitor can use the following method. Set the multimeter to the R×10k range, and select two transistors 3DC6 (or 9013) with a value greater than 100 to form a composite tube. The circuit schematic is shown in Figure 2. The amplification effect of the composite tube is used to amplify the charging current of the capacitor under test to increase the swing range of the multimeter pointer. Connect the capacitance to be measured between the base b and collector c of the composite tube. The red and black test leads of the multimeter are connected to the emitter e and collector c of the composite tube respectively. If the pointer of the multimeter swings slightly and then returns to infinity, the capacitor is normal; if the pointer does not move or cannot return to infinity, the capacitor is damaged. During the test operation, especially when measuring small capacitance capacitance, it is necessary to repeatedly exchange the two points of contact between the pins of the capacitor under test to clearly see the swing of the multimeter pointer.
