How to test capacitors with a multimeter Capacitors are one of the most commonly used electronic components. The shape of the capacitor and the circuit symbol Color? -10 shown. The universal symbol for capacitors is "C". Capacitors are mainly composed of metal electrodes, dielectric layer and electrode leads, the two electrodes are insulated from each other. Therefore, it has the basic performance of "isolation current AC".
With a digital multimeter to detect the capacitor, can be carried out in the following ways.
One, with the capacitance of direct detection of some digital multimeter has the function of measuring capacitance, the range is divided into 2000p, 20n, 200n, 2μ and 20μ five files. Measurement can be discharged capacitance two pins directly into the table on the Cx jack, select the appropriate range can be read after the display data.
2000p, suitable for measuring capacitance less than 2000pF; 20n, suitable for measuring capacitance between 2000pF and 20nF; 200n, suitable for measuring capacitance between 20nF and 200nF; 2μ, suitable for measuring capacitance between 200nF and 2μF; 20μ, suitable for measuring capacitance between 2μF and 20μF.
Experience has shown that some models of digital multimeter (e.g., DT890B +) in the measurement of 50pF below the small capacitance when the error is large, the measurement of the capacitance of 20pF below the almost no reference value. At this time, you can use the series connection method to measure small value capacitors. Method is: first find a 220pF or so of capacitance, with a digital multimeter to measure the actual capacity of C1, and then to be measured in parallel with the small capacitance to be measured out of its total capacity of C2, then the difference between the two (C1 - C2) that is to be measured the capacity of the small capacitor. With this method to measure 1 ~ 20pF of small capacitance is very accurate.
Two, with the resistance file detection practice has proved that the use of digital multimeter can also observe the charging process of capacitors, which is actually a discrete digital quantities to reflect the changes in charging voltage. Set the digital multimeter measurement rate of n / s, then in the observation of the capacitor charging process, every second to see n independent of each other and the sequential increase in the number of readings. According to this display feature of the digital multimeter, you can test the capacitor and estimate the size of the capacitance. The following is the use of digital multimeter resistance file detection of capacitors, for not set the capacitance file of the instrument is very practical. This method is suitable for measuring 0.1μF ~ several thousand microfarads of large-capacity capacitors.
1.Measurement method of operation will be dialed to the appropriate digital multimeter resistance gear, the red pen and black pen were in contact with the measured capacitor Cx poles, then the display value will start from "000" gradually increased until the display overflow symbol "1". If "000" is always displayed, the value will increase gradually until the overflow symbol "1" is displayed. If always show "000", the capacitor internal short circuit; if always show overflow, the capacitor may be internal open circuit between the poles, but also when the selected resistance gear is not appropriate. Check electrolytic capacitors need to pay attention to, the red pen (positively charged) connected to the positive terminal of the capacitor, the black pen connected to the negative terminal of the capacitor.
2. Measurement principle of measuring capacitors with resistance gear measurement principle. Measurement, the positive power supply through the standard resistance R0 to the measured capacitor Cx charging, just started charging the moment, because Vc = 0, so the display "000". With the gradual increase of Vc, the display value increases. When Vc = 2VR, the meter starts to display the overflow symbol "1". The charging time t is the time required for the display to change from "000" to overflow, and this time interval can be measured by a quartz meter.
3. Using the DT830 type digital multimeter to estimate the capacitance of the measured data using the DT830 type digital multimeter to estimate the capacitance of 0.1 μF ~ thousands of microfarads of capacitors, in accordance with the Table 5-1 selection of the resistance file, the table gives a range of capacitance can be measured and the corresponding charging time. The data listed in the table is also a reference value for other models of digital multimeter.
The principle of selecting the resistance range is: when the capacity is small, it is appropriate to choose a high resistance range, and when the capacity is large, it should be used in a low resistance range. If the high resistance gear estimate large-capacity capacitors, due to the charging process is very slow, the measurement time will last a long time; if the low resistance gear check small-capacity capacitors, due to the charging time is very short, the meter will always show the overflow, can not see the change process.