Summary of usage skills of multimeter in home appliance maintenance
When using a multimeter, attention should be paid to:
1) Identify the functions of each range of the multimeter
2) Measure three to four resistances and record them
3) Measure the AC voltage and record it
4) Measure the DC voltage and record it
Multimeter: mainly used to measure AC and DC voltage, current, DC resistance, and transistor current amplification bits. Currently, there are two common types: digital multimeter and mechanical multimeter
1) Digital multimeter
On the multimeter, you will see a conversion knob as shown in the figure, which refers to the gear position of the secondary quantity
V~: Refers to the gear position for measuring AC voltage
V -: Refers to the DC voltage measurement gear
MA: Refers to the gear position for measuring DC voltage
Ω (R): Refers to the gear used to measure resistance
HFE: Refers to the gear used to measure 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, convenient and accurate reading (digital display)
2) Mechanical multimeter
The appearance of a mechanical multimeter is somewhat different from that of a digital meter, but their shift knobs are similar and their gear positions are also basically the same
On the mechanical watch, you will see a dial as shown in the picture, with eight scales on the dial:
The scale marked with "Ω" is used for measuring resistance
The scale marked with "~" is used to measure AC/DC voltage and DC current
The scale marked with "HFE" is used for measuring the transistor
The scale marked with "LI" measures the current and voltage of the load
The scale marked with "DB" measures the level
3) Use of a multimeter
① Digital multimeter: Before measuring, set the gear to the measurement position. It should be noted that the range marked on the gear position is the maximum value
② Mechanical multimeter: The method for measuring current and voltage is the same as the mathematical equation, but when measuring negative current, the reading must be multiplied by the value on the gear to obtain the measured value. For example, the current gear is "X100", the reading is 200, and the measurement question is "200X100=20000 Ω=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) Precautions:
① Adjust the "zero point" (only available in mechanical watches). Before using the watch, first check if the pointer is pointing to the "zero position" on the left end. If it is not, slowly turn the "starting zero position" correction screw in the center of the watch case with a small screwdriver to make the pointer point to the zero position
② When using a multimeter, it should be placed horizontally (mechanical only)
③ Before testing, it is necessary to determine the measurement content and turn the range conversion knob to the corresponding measurement position shown to avoid burning the meter head. If the size of the measured physical quantity is not known, it is necessary to start testing from a large range
④ The pen should be correctly inserted into the corresponding socket
⑤ During the testing process, do not arbitrarily rotate the gear change knob
⑥ After use, be sure to adjust the gear change knob to the maximum range of AC voltage
⑦ When measuring DC voltage and current, attention should be paid to the positive and negative terminals of the voltage, the flow direction of the current, and the correct connection with the probe
