Detailed Explanation of Digital Multimeter Capacitance File and Capacitance Measurement Method
Not all digital meters have a capacitance range. If you are not sure, you can check whether there is a mark "F" on the turntable of your digital watch or you can choose a marked capacitance range. For example, the digital watch in the picture above has 20 The mark of the m F range indicates that the capacitance range is 20 m F, that is, 20000 uF, and there is only one gear, so there is no need to consider the problem of range mismatch when measuring.
Let's take a 100 uF polar capacitor as an example. Remember to discharge the capacitor before measuring, otherwise it may burn out the multimeter. The discharge method is also very simple. If you want to be lazy, you can directly short the two pins. Connected, but it is better to connect a resistor in series in the middle.
After charging the capacitor, you can measure it. Connect the test lead to both ends of the polar capacitor (it is better to connect the red test lead to the positive pole of the polar capacitor, and the black test lead to the negative pole of the polar capacitor). If the capacitance is normal, you can see it after a while. To the capacity of the capacitor displayed on the multimeter, for example, the capacitor marked 100 uF, the actual measurement result is 103.8 uF.
When measuring capacitance, the precautions are similar to measuring resistance. Remember not to touch the two test leads at the same time, so as not to affect the measurement results.
How to measure aluminum electrolytic capacitors with the capacitance file of a digital multimeter ()
1. The capacity value of the electrolytic capacitor cannot be measured online, because there are distributed factors in the circuit, which are inaccurate in most cases and must be measured after soldering.
2. If you must judge whether the electrolytic capacitor is invalid online, please use the ESR meter (equivalent series resistance) to judge. Online measurement of ESR values can quickly pick out problematic electrolytic capacitors.
3. The measurement of electrolytic capacitors is not like measuring resistance. It is difficult to judge whether the electrolytic capacitor is good or bad after one measurement. The error of measuring electrolytic capacitors with the capacitance gear of general digital multimeters is relatively large.
How to measure capacitance with a multimeter
The measurement of the capacitor can only be judged accurately with a mechanical watch.
Turn the multimeter to 1K or 100 ohm, and connect the two test leads to the two electrodes of the capacitor under test. Observe the reaction of the hands of the watch. If the hands of the watch quickly approach zero, then slowly go back (towards infinity), and stop somewhere, it means that the capacitor is basically good. The closer the return stop position is to infinity, the better the quality, and the farther it is, the more leakage. If the needle of the multimeter quickly swings to the zero position or close to the zero position and does not move, it means that the two poles of the capacitor have a short circuit fault and cannot be used. If the needle does not move at all when the test lead and the two poles of the capacitor are connected, it means that the internal connection of the capacitor has been disconnected and cannot be used.
