How to use a 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. There are currently two common types of digital multimeters and mechanical multimeters.
1) Digital multimeter
On the multimeter, you will see a conversion knob as shown in the figure, which refers to the gear of the secondary quantity.
V~: represents the gear for measuring AC voltage.
V -: represents the gear for measuring DC voltage.
MA: Refers to the gear used to measure the DC voltage.
Ω (R): represents the gear used to measure resistance.
HFE: Refers to the gear used to measure resistance.
The red pen on the multimeter indicates the positive pole of the external circuit, while 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 for measuring AC/DC voltage and DC current.
The scale marked with "HFE" is used to measure the transistor.
The scale marked with "LI" measures the current and voltage of the load.
The scale marked with "DB" measures the level.
3) The 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 is the maximum value.
② Mechanical multimeter: The method of measuring current and voltage is the same as the mathematical formula, but when measuring the 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=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) Notes:
① Adjust the "zero point" (only available in mechanical watches). Before using the watch, check if the pointer is pointing to the left "zero position". 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 The multimeter should be placed horizontally when in use (mechanical only)
③ Before testing, it is necessary to determine the measurement content and turn the range conversion knob to the corresponding measurement gear 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 inserted correctly into the corresponding socket.
⑤ During the testing process, do not rotate the gear change knob arbitrarily.
⑥ After use, be sure to adjust the gear change knob of the non meter to the 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 direction of the current flow, and the connection with the meter probe
