How to use the resistance range of a multimeter (mechanical meter) to judge the quality of a capacitor

1. Check the quality of electrolytic capacitors with the resistance range of a multimeter
The two leads of electrolytic capacitors are divided into positive and negative. When checking the quality of electrolytic capacitors with lower withstand voltage (6V or l0V), the resistance range should be set to R×100 or R×1K. Connect the red test lead to the negative end of the capacitor and the black test lead to the positive end. At this time, the pointer of the multimeter will swing and then return to zero or near zero. Such electrolytic capacitors are good. The larger the capacity of the electrolytic capacitor, the longer the charging time, and the slower the pointer swings.

2. Use a multimeter to determine the positive and negative leads of electrolytic capacitors
For some electrolytic capacitors with lower withstand voltage, if the positive and negative lead marks are unclear, you can judge based on its characteristics that the leakage current is small (the resistance value is large) when it is positively connected and the leakage current is large when it is reversely connected. The specific method is: use the red and black test pens to touch the two leads of the capacitor, remember the size of the leakage current (resistance value) (the resistance value indicated when the pointer swings back and stops), then short-circuit the positive and negative leads of the capacitor, swap the red and black test pens, and then measure the leakage current. The judgment is based on the indication of the small leakage current. The lead that contacts the black test pen is the positive end of the electrolytic capacitor. This method is more difficult to distinguish the polarity of electrolytic capacitors with small leakage current.

3. Check the variable capacitor with a multimeter
The variable capacitor has a set of fixed plates and a set of moving plates. Use the resistance range of the multimeter to check whether there is any contact between the moving and fixed plates. Use the red and black test leads to connect the moving and fixed plates respectively, rotate the shaft handle, and the meter pointer does not move, indicating that there is no short circuit (touching plate) between the moving and fixed plates; if the pointer swings, it means that there is a short circuit in the capacitor.

4. Use the resistance range of the multimeter to roughly identify the quality of capacitors with a capacity of more than 5000PF The resistance range of the multimeter
can be used to roughly identify the quality of capacitors with a capacity of more than 5000PF (those below 5000PF can only be used to determine whether the capacitor is broken down). When checking, set the resistance range to the high value of the range, and the two test pens are in contact with the two ends of the capacitor. At this time, the pointer swings quickly and then recovers. Reverse connection, the swing amplitude is larger than the first time, and then recovers. Such a capacitor is good. The larger the capacity of the capacitor, the larger the swing of the meter pointer during measurement, and the longer the time it takes for the pointer to recover. We can compare the size of the capacity of the two capacitors based on the swing of the meter pointer.