Application of Multimeter in Home Appliance Maintenance
The use of multimeters in home appliance repairs When using multimeters, you need to pay attention to:
1). Identify the functions of each file 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: It is mainly used to measure AC and DC voltage, current, DC resistance, and transistor current amplification digits, etc. Now there are mainly two types of digital multimeters and mechanical multimeters.
1) Digital multimeter
On the multimeter, you will see the conversion knob as shown in the figure, and the knob refers to the gear position of the secondary quantity.
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 range of measuring resistance.
HFE: Indicates the scale of measuring resistance.
The red pen of the multimeter indicates that it is connected to the positive pole of the external circuit, and the black pen indicates that it is connected to 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 the gear knobs and gear positions of the two are similar.
On a mechanical watch, you will see a dial as shown in the figure, and there are eight scales on the dial:
The one marked with "Ω" is the scale used for measuring resistance.
The ones marked with "~" are scales used for measuring AC and DC voltages and DC currents.
The one marked with "HFE" is the scale used when measuring the triode.
Marked with "LI" is the scale for measuring the current and voltage of the load.
The one marked with "DB" is the scale for measuring the level.
3) Use of multimeter
①Digital multimeter: Before measuring, switch to the measurement position. It should be noted that the range marked on the position is the maximum value.
②Mechanical multimeter: The method of measuring current and voltage is the same as the mathematical formula, but when measuring the cathode, the reading must be multiplied by the value on the gear to get 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). Precautions:
① Adjust the "zero point" (only for mechanical watches). Before using the watch, first check that the pointer is on the "zero position" at the left end. Adjust the screw so that the pointer points to zero.
②When the multimeter is used, it should be placed horizontally (only for machines)
③Before the test, determine the measurement content, turn the range conversion knob to the corresponding gear for the measurement shown, so as not to burn the meter head, if you do not know the size of the measured physical quantity, start the test with a large range first.
④The test leads should be correctly inserted into the corresponding sockets.
⑤During the test, do not rotate the gear change knob arbitrarily.
⑥ After use, be sure to adjust the range change knob of the unused meter 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 flow direction of the current, and connect (when) correctly with the test leads.
