Precautions for measuring DC voltage with a multimeter
How to measure DC voltage with a multimeter, use the DC voltage block of the multimeter to measure the DC power supply voltage and the working voltage of peripheral components, and the precautions for measuring DC voltage for your reference.
How to measure DC voltage with a multimeter
When the power is on, use the DC voltage block of the multimeter to measure the DC power supply voltage and the working voltage of the peripheral components; detect the DC voltage value of each pin of the IC to the ground, and compare it with the normal value, and then compress the fault range and find the damaged components. .
Notes on measuring DC voltage:
1. The multimeter must have a large enough internal resistance, at least 10 times greater than the resistance of the circuit under test, so as to avoid large measurement errors.
2. Usually, turn each potentiometer to the middle position. If it is a TV, the signal source should use a standard color bar signal generator.
3. Take anti-skid measures for test pens or probes. The IC is easily damaged due to any momentary short circuit. The following methods can be taken to prevent the test pen from sliding: take a piece of bicycle valve core and put it on the test pen tip, and grow the test pen tip by about 0.5mm. It will not short-circuit even if it hits adjacent points.
4. When the measured voltage of a certain pin is inconsistent with the normal value, the quality of the IC should be judged by analyzing whether the voltage of the pin has an important influence on the normal operation of the IC and the corresponding changes in the voltages of other pins.
5. IC pin voltage will be affected by peripheral components. When there is leakage, short circuit, open circuit or change in value of peripheral components, or the peripheral circuit is connected to a potentiometer with variable resistance, the position of the potentiometer sliding arm will vary, which will cause the pin voltage to change.
6. If the voltage of each pin of the IC is normal, it is generally considered that the IC is normal; if the voltage of some pins of the IC is abnormal, you should start from the maximum deviation from the normal value to check whether the peripheral components are faulty. If there is no fault, the IC is likely to be damaged.
7. For a dynamic receiving device, such as a TV, the voltage of each pin of the IC is different when there is a signal or not. If it is found that the pin voltage should not change but changes greatly, and the voltage that changes with the signal size and the different positions of the adjustable components does not change, it can be determined that the IC is damaged.
8. For devices with multiple working modes, such as video recorders, under different working modes, the voltage of each pin of IC is also different.
