How to measure DC working voltage with a multimeter?
There are eight points to pay attention to when measuring DC working voltage with a multimeter. The IC pin voltage will be affected by peripheral components. If there is no fault, the IC is likely to be damaged. Anti-slip measures should be taken for the test leads or probes.
1. When the measured voltage of a certain pin does not match the normal value, the quality of the IC should be judged based on whether the pin voltage has any important impact on the normal operation of the IC and the corresponding changes in the voltage of other pins.
2. The IC pin voltage will be affected by peripheral components.
When peripheral components leak, short circuit, open circuit or change value, or the peripheral circuit is connected to a potentiometer with variable resistance, the pin voltage will change due to different positions of the potentiometer's sliding arm.
3. 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 point that deviates the most from the normal value and check whether the peripheral components are faulty. If there is no fault, the IC is likely to be damaged.
4. For dynamic receiving devices, such as TVs, the voltages of each IC pin are different when there is a signal or not.
If it is found that the pin voltage should not change but changes greatly, and it should change with the signal size and the position of the adjustable component but does not change, it can be determined that the IC is damaged.
5. For devices with multiple working modes, such as video recorders, the voltages of each IC pin are also different in different working modes.
6. The multimeter must have a large enough internal resistance, at least 10 times greater than the resistance of the circuit being measured, to avoid large measurement errors.
7. Usually, turn each potentiometer to the middle position. If it is a TV, the signal source should use a standard color bar signal generator.
8. Anti-slip measures should be taken for test leads or probes.
Any instantaneous short circuit can easily damage the IC. It is necessary to prevent the test lead from sliding. The measures are as follows: take a piece of bicycle valve core and put it on the test lead tip, and extend the test lead tip by about 0.5mm. This can make the test lead tip well connected with the point being tested. contact, it can effectively prevent slipping, and there will be no short circuit even if it hits a nearby point.
