Method of measuring capacitance with multimeter

Today I will share with you a method to measure capacity. The method is very simple. Since we want to measure capacitance, we just take out the multimeter to observe the gear for measuring capacitance and whether the position of the needle needs to be changed. The editor only has the multimeter shown in the picture below, so I can only take the following model as an example. In fact, there are many types of multimeters, like the second picture below is another one, but the measurement methods of different multimeters are basically the same. If you learn one, you can basically learn all of them.

In the picture above, we can see that there is a capital "f" sign in the lower left corner of the dial. In fact, it represents the gear for measuring capacitance, which is named after the international unit of capacitance, Farad. The next step is to rotate the needle to a range larger than the capacitance being measured. In fact, the closer the better. For ease of operation, we directly use the maximum range of the multimeter. In addition, we need to see if the position of the needle needs to be changed. Generally, the position of the black test lead has a fixed sign "com", so we only need to change the position of the red test lead. The symbol of capacitance is "c", and there is a "cx" on the multimeter, so we can insert the red test lead into this hole.

Next we can measure. The picture below shows a washing machine capacitor. This type of capacitor is relatively large and has a high withstand voltage, but its capacity is not large compared to aluminum electrolytic capacitors. There is no distinction between positive and negative poles, so the two test leads can be connected at will during measurement. However, one thing to note is that the hands cannot touch the two test leads at the same time, as this will affect the measurement results. If the operation is correct, the capacitance measured at this time can be seen on the multimeter. The capacitor in the video is marked as 4uf, and the measured value is 4.3uf.

The washing machine capacitor mentioned above does not distinguish polarity, which is easier to understand, but there is another type of polar capacitor, which has polarity. If it is a new polar capacitor, the long pin is the positive pole and the short pin is the negative pole. The one soldered on the board can be distinguished by the outer packaging. In short, it has polarity. So when we use a multimeter to measure its capacity, do we also need to distinguish between positive and negative poles?

Talking is useless, let's actually test it. The figure below is measured according to the normal order of understanding, that is, the red test lead is connected to the positive pole and the black test lead is connected to the negative pole. At this time, we can see on the multimeter's display that the measured capacitance is 109uf, and there is no "-" sign in front of the number.

Then we change the order of the capacitor pins, that is, connect the red test lead to the negative pole of the capacitor, and the black test lead to the positive pole of the capacitor, and then look at the size of the capacitor measured at this time. The figure below is the size of the capacitor measured by changing the order of the capacitor pins. We can clearly see that the size measured at this time is 109.2uf, which is almost the same as the capacity measured last time, and there is no "-" mark in front of the number. Therefore, we can assume that when using a multimeter to measure the size of the polarity capacitor, it has nothing to do with the order in which the pins are connected.

When measuring with a multimeter, you do not need to distinguish the polarity of the capacitor, but this does not mean that the polarity of the capacitor is not distinguished when it is soldered to the circuit board. If the capacitor is soldered to the circuit board, it can easily cause the capacitor to explode if it is accidentally soldered backwards. Therefore, we must pay attention to the polarity of the capacitor when soldering the circuit.