How to use a multimeter to test some common electronic components

Whenever a circuit board fails to operate normally and the circuit is found to be fine after inspection, it is very likely that an electronic component is broken. If you want to repair it, you must find the problematic component and replace it. However, finding the problematic component is a technical job and requires certain skills. Today I will teach you how to use a multimeter to detect some commonly used electronic components.

Resistance detection

The most direct way to detect resistance is to measure it with the resistance range of a multimeter. Generally, the resistance size will be marked on the resistor. Select the appropriate resistance range and connect the red and black test leads to both ends. If the readings are close, it is normal, otherwise it is broken. When measuring large resistance, be careful not to touch the red and black test leads with both hands. It is not dangerous, but to ensure the accuracy of the resistance measurement. It is okay to touch one of the test leads with your hand.

Potentiometer detection

Normally, a potentiometer has three pins. First, use a multimeter to select the resistance range to test whether the resistance between two of the three pins is the same as or close to the marked resistance value. If there is a big difference, it means that the potentiometer is damaged. If it is normal, continue to measure the two pins with the multimeter, and then rotate the potentiometer counterclockwise to a position close to the off position. At this time, the smaller the resistance, the better. Then rotate it clockwise. If the resistance gradually increases and the final resistance is close to the marked resistance, the potentiometer is normal.

Fixed capacitor detection

In addition to using a multimeter to select the appropriate range of the capacitance range to measure capacitance values, you can also use the resistance range to measure. When measuring, you must select the appropriate resistance range and use two test leads to connect the two pins of the capacitor respectively. The resistance should be infinite. If the resistance is 0, the capacitor is damaged.

Electrolytic capacitor testing

The measurement methods of electrolytic capacitors and fixed capacitors are a little different. Of course, you can choose to use the capacitance block for detection, which everyone knows. Let me talk about the method of measuring with the capacitance block. First, select the appropriate resistance block, and the red and black test leads touch the two poles of the capacitor respectively. At this time, the displayed value will increase from 0 until the overflow symbol 1 is displayed. If it always displays 0, it means that the capacitor is short-circuited internally. If it always displays 1, it means that the capacitor is open between the poles. It is also possible that the resistance block is not selected appropriately. Here you must pay attention. When measuring, since electrolytic capacitors have positive and negative poles, you must not connect them reversely. Usually, the red test lead is connected to the anode of the capacitor (the one with the long leg), and the black test lead is connected to the cathode of the capacitor (the one with the short leg). The pointer of the multimeter is just the opposite.

Inductance detection

Similarly, select the resistance range of the multimeter and connect the test leads to both ends of the inductor. If the measured resistance value is zero, the inductor is short-circuited internally. Under normal circumstances, the DC resistance of the inductor being measured is directly related to the diameter of the enameled wire used to wind the inductor coil and the number of wire windings. As long as the resistance value can be measured, the inductance can be considered normal.

Diode detection

Set the multimeter to the diode detection position, connect the red test lead to the anode of the diode and the black test lead to the cathode of the diode. If the display shows the voltage drop of the diode (usually 0.5 for silicon tubes and 0.2 for germanium tubes), the diode is normal. Replace the test leads. If the display shows 1, it is normal, otherwise it is broken down. If the results of both tests are 0 or 1, the diode is damaged.

Light Emitting Diode Detection

Similarly, set the digital multimeter to the diode detection position, touch the anode of the LED with the red test lead, and the cathode of the LED with the black test lead (same as the diode above). If you see it glow, it is normal, otherwise it is damaged.