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Understand the use of the multimeter and maintenance tips

Multimeters, also known as multiplex tables, multimeters, tri-meters, and multi-use meters, are indispensable measuring instruments for power electronics and other departments. Generally, voltage, current and resistance are the main purposes. The multimeter is divided into a pointer multimeter and a digital multimeter according to the display mode. It is a multi-functional, multi-range measuring instrument. The general multimeter can measure DC current, DC voltage, AC current, AC voltage, resistance and audio level, etc. Some can also measure AC current, capacitance, inductance and semiconductor. Some parameters.
How to use the multimeter
1. Be familiar with the functions of the multimeter before use. According to the object to be measured, select the gear position, range and pen jack correctly.
2. When the size of the measured data is unknown, the range switch should be set to the maximum value, and then switched from the large range to the small range, so that the meter pointer can be indicated at 1/2 or more of the full scale.
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3. When measuring the resistance, after selecting the appropriate magnification file, touch the two test leads to make the pointer point to zero. If the pointer deviates from the zero position, adjust the “zero adjustment” knob to zero the pointer to ensure accurate measurement results. . If you can't zero or the digital display sends a low voltage alarm, you should check it in time.
4. When measuring the resistance of a certain circuit, the power of the circuit under test must be cut off.
5. When using a multimeter for measurement, pay attention to the safety of personal and instrumentation equipment. Do not touch the metal part of the test pen by hand during the test. Do not switch the gear switch with power to ensure accurate measurement and avoid accidents such as electric shock and burning of the instrument. .
Multimeter maintenance
1. Do not connect more than 1000V DC voltage or higher than 700V AC RMS voltage.
2. Do not connect the voltage source while the function switch is in Ω and position.
3. Do not use this watch when the battery is not installed or the back cover is not tightened.
Multimeter repair
1. Visual inspection
If it is found that such as wire breakage, desoldering, short circuit, fuse tube break, burnt component, etc., you can touch the temperature rise of the battery, resistor, transistor, and integrated block. Refer to the circuit diagram to find out the cause of abnormal temperature rise.
2. Voltage measurement
Measure whether the working voltage of each key point is normal, and find the fault point faster. Such as measuring the operating voltage, reference voltage of the A / D converter.
3. Short circuit method
The short circuit method is generally used in the A/D converter method. This method is used more often when repairing weak current and micro electric instruments.
4. Open circuit method
Disconnect the suspicious part from the whole unit or unit circuit. If the fault disappears, it indicates that the fault is in the disconnected circuit. This method is mainly suitable for the case where the circuit is short-circuited.
5. Measuring element method
When the fault has been reduced to somewhere or several components, it can be measured online or offline. If necessary, replace it with a good component. If the fault disappears, the component is broken.

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