Testing method for capacitance of chip capacitors

The capacitance is usually measured with a capacitance bridge, which can get the accurate capacitance. In the absence of special instruments, the capacitance of the capacitor can be estimated with the high resistance of a multimeter, but it is only suitable for the measurement of large-capacity capacitors.

The following is a method for using a multimeter to detect the capacitance of an electrolytic capacitor. First, set the ohmmeter of the multimeter to the R x 1k position, and short-circuit the probes to zero. Connect the black probe of the multimeter to the positive pole of the electrolytic capacitor and the red probe to the negative pole of the electrolytic capacitor, as shown in Figure 4-9. Since the capacitor is not charged at first, when the two probes are just connected to the capacitor, the battery in the multimeter charges the capacitor through the probes. As the current flows through the circuit, the needle of the multimeter deflects. The larger the positive pole of the capacitor, the larger the deflection angle of the needle. If the capacitance is small, the deflection angle of the needle is small during detection. Based on this principle and the experience of actual detection, the position where the needle should deflect corresponding to different capacitances can be given to determine the capacitance of the capacitor being measured. The relationship between the needle deflection position and the capacitance is shown in Table 4-13 for reference during detection.
        
        
As the amount of charge on the capacitor increases, the charging current becomes smaller and smaller. If the capacitor does not leak electricity, after a period of time, when the voltage on the capacitor is equal to the battery voltage, the charging current will decrease to zero, and the multimeter needle will slowly return from the initial deflection position to the position of infinite resistance (i.e. the starting point). In fact, electrolytic capacitors always have leakage current, and the needle cannot return to the starting point. It is generally believed that as long as the needle can cross the 200 scale when returning, the leakage current is very small and the capacitor can be used.
       
After the test, the two pins of the capacitor should be short-circuited for discharge to prevent it from being affected when retesting.