Digital multimeter to test the continuity of wires

　　1. Digital multimeter is a powerful tool for electronic measurement. It can be used to measure the continuity of circuits in daily life. Multimeters are divided into digital multimeters and pointer multimeters. Generally, they are divided into voltage range (AC + DC), current range (AC + DC), and resistance range. The resistance range is used to measure continuity, which is the simplest function.

　　2. Let's take a dental probe as an example. The probe is a plastic handle with two metal needles connected, which is similar to our usual skinned wires. In order to determine whether point A and point B are conductive, we use the following steps:

　　1) First, make sure the wiring is correct. Insert the black wire into the COM port and the red wire into the V (omiga, or diode port)

　　2) Set the gear to 200 on the resistance scale, or the "buzzer, diode" scale.

　　3) Connect a red or black pen to the A and B terminals to be measured. If A and B are disconnected, the LCD screen will display "1", indicating infinite resistance.

　　4) Use the same method to measure points A and C to determine whether they are connected. If the wire is connected, there will be a buzzer prompt sound, and the LCD screen will display a number close to "0", in this case it will display "0.001"; when using the resistance range, if the wire is connected, it will display a jumping number less than 200. The accuracy of the multimeter is different, and the measurement number is also different, but when it is connected, it will be a number close to zero.

　　The above method can be applied in daily life, such as measuring the continuity of wires, the on and off of electrical switches, etc.

　　3. In daily life, there are other devices that can also be measured in this way, such as headphones and speakers, but their resistance will be slightly larger. The figure below is a schematic diagram of a headphone. You can see that there are two channels, left and right. In fact, the common end and the left and right channel ends are connected to a coil respectively, which vibrates and makes sound when powered on. The resistance of the coil is generally 30-100 ohms.

　　4. When measuring, you can connect the red and black test leads to the common terminal and the left and right channel terminals respectively. Be careful not to touch the wires between the red and black test leads. As shown in the example below, the resistance between the left channel and the common terminal is 33 ohms, indicating that this channel is normal. The same method can be used to judge the other channel.

　　5. For pointer multimeter:

　　1) Connect the red and black test leads correctly

　　2) Connect the red and black test leads to both ends of the line to be measured

　　3) If the pointer resistance is close to zero or relatively small, it means the line is connected. If it does not move or the resistance is very large, it means the line is disconnected.