The method of measuring capacitance with a multimeter by using the resistance range.
Practice has proved that a digital multimeter can also be used to observe the charging process of a capacitor. In fact, this reflects the change of the charging voltage in discrete digital quantities. Suppose the measurement rate of the digital multimeter is n times per second. During the observation of the capacitor's charging process, n independent and successively increasing readings can be seen every second. Based on this display characteristic of the digital multimeter, the condition of the capacitor can be detected and the capacitance value can be estimated. The following is the method of detecting a capacitor using the resistance range of a digital multimeter, which is very useful for meters without a capacitance range. This method is suitable for measuring large - capacity capacitors from 0.1 μF to several thousand microfarads.
Set the digital multimeter to an appropriate resistance range. Touch the two poles of the capacitor Cx to be measured with the red and black probes respectively. At this time, the display value will gradually increase from "000" until the overflow symbol "1" is displayed. If "000" is always displayed, it indicates that there is a short - circuit inside the capacitor. If the overflow is always displayed, it may be due to an open - circuit between the internal poles of the capacitor, or the selected resistance range may be inappropriate. When checking an electrolytic capacitor, note that the red probe (positively charged) should be connected to the positive pole of the capacitor, and the black probe to the negative pole.
Method of Measuring Capacitance with a Multimeter Using the Capacitance Range
Some digital multimeters have the function of measuring capacitance, and their ranges are divided into five levels: 2000p, 20n, 200n, 2μ, and 20μ. During measurement, directly insert the two leads of the discharged capacitor into the Cx jack on the meter panel. After selecting an appropriate range, the displayed data can be read. The 2000p range is suitable for measuring capacitors less than 2000 pF; the 20n range is suitable for measuring capacitors between 2000 pF and 20 nF; the 200n range is suitable for measuring capacitors between 20 nF and 200 nF; the 2μ range is suitable for measuring capacitors between 200 nF and 2 μF; the 20μ range is suitable for measuring capacitors between 2 μF and 20 μF.
Experience has shown that some models of digital multimeters (such as DT890B +) have relatively large errors when measuring small - capacity capacitors below 50 pF, and the measurement of capacitors below 20 pF has little reference value. In this case, the series method can be used to measure small - value capacitors. The method is as follows: First, find a capacitor of about 220 pF and measure its actual capacitance C1 with a digital multimeter. Then, connect the small capacitor to be measured in parallel with it and measure the total capacitance C2. The difference between the two (C2 - C1) is the capacitance of the small capacitor to be measured. This method is very accurate for measuring small - capacity capacitors from 1 pF to 20 pF.
