The use of multimeter in home appliance maintenance

Things to note when using a multimeter:

1) Identify the functions of each gear of the multimeter.
2) Measure three to four resistors and record them.
3) Measure AC voltage and record them.
4) Measure DC voltage and record them.

Multimeter: Mainly used to measure AC and DC voltage, current, DC resistance, and transistor current amplification digits, etc. There are two common types of multimeters: digital multimeters and mechanical multimeters.

1) Digital multimeter

On the multimeter, you will see a conversion knob as shown in the figure. The knob indicates the gear of the secondary measurement.

V~: indicates the gear for measuring AC voltage.
V-: indicates the gear for measuring DC voltage.
MA: indicates the gear for measuring DC voltage.
Ω(R): indicates the gear for measuring resistance.
HFE: indicates the gear for measuring resistance.

The red pen of the multimeter indicates the positive pole of the external circuit, and the black pen indicates the negative pole of the external circuit.
Advantages: anti-magnetic, easy to read, accurate (digital display)......

2) Mechanical multimeter

The appearance of a mechanical multimeter is somewhat different from that of a digital meter, but the gear knobs of the two are similar, and the gears are basically the same.

On a mechanical meter, you will see a dial as shown in the figure, with eight scales on the dial:

the scale marked with "Ω" is used to measure resistance.
The scale marked with "~" is used to measure AC and DC voltage and DC current.
The scale marked with "HFE" is used to measure transistors.
The scale marked with "LI" is used to measure the current and voltage of the load.
The scale marked with "DB" is used to measure the level.

3) Use of multimeter

① Digital multimeter: Before measuring, turn to the measuring gear. It should be noted that the gear marked is the range, that is, the maximum value.
② Mechanical multimeter: The method of measuring current and voltage is the same as the mathematical formula, but when measuring voltage, the reading must be multiplied by the value on the gear to obtain the measured value. For example: the current gear is "X100" and the reading is 200, the measurement question is 200X100=20000Ω=20K, the "Ω" scale on the dial is from left to right, from large to small, while the others are from left to right, from small to large

4) Notes:

① Adjust the "zero point" (only for mechanical meters). Before using the meter, first check that the pointer is pointing to the "zero position" on the left end. If not, use a small screwdriver to slowly turn the "starting point zero position" correction screw in the center of the case to make the pointer point to the zero position.
② The multimeter should be placed horizontally when used (only for mechanical meters)
③ Before testing, determine the measurement content and turn the range conversion knob to the corresponding gear position shown to avoid burning the meter head. If you don't know the size of the physical quantity to be measured, start the test from a large range.
④ The test leads should be correctly inserted into the corresponding sockets.
⑤ During the test, do not rotate the gear conversion knob arbitrarily.
⑥After use, be sure to adjust the unused meter position change knob to the maximum range of AC voltage.
⑦When measuring DC voltage and current, pay attention to the positive and negative poles of the voltage, the direction of the current, and the correct connection of the meter leads.