Resistor fault measurement and modification method
1. Fault measurement method of resistor:
(1) Measuring method of digital multimeter (take DT9208 as an example)
When measuring the resistance of the resistor, the digital multimeter should be set to the appropriate range. If the resistance value of the resistor to be measured is 3 kΩ, the range of the multimeter should be set to 20 k. The two test leads respectively touch the two ends of the resistor that needs side measurement, as shown in Figure 1-30. At this time, the resistance of the resistor is displayed digitally.
In order to improve the accuracy of side measurement, be careful not to hold both ends of the resistor and the test lead with two hands, as shown in Figure 1-31. Because this is equivalent to connecting a human body resistor in parallel with the resistor on the passive side. This effect is more obvious when the resistance value of the side measurement is large, and the resistance value of the side measurement is reduced.
(2) Measuring method of pointer multimeter
When measuring the resistance of the resistor, the pointer multimeter should be set to the appropriate range of the most resistor on the side. As shown in the figure, the two test leads should be touched and short-circuit the zero adjustment potentiometer to adjust the pointer of the multimeter to ” At the zero point of the “Ω” scale line, touch the test leads to the two ends of the resistor to be tested. At this time, the reading on the “Ω” scale line is the resistance value of the resistor.
Troubleshooting methods for resistors:
(1) If the resistor body is broken, scorched, or the lead wire is broken, it can be judged by appearance observation. Broken resistors should be replaced.
The scorched resistors, even when they are on the double side, have not found any changes in resistance, and should be replaced at this time. Because after the resistor is scorched, the noise figure will increase, which is most prone to noise. After the scorched resistor is energized, the resistance value is also unstable.
When the lead wire is broken, the protective paint on the broken end or the cap can be scraped off, and a new lead wire can be welded again. The operation should be fast when welding, so as to avoid the resistance value of the resistor from being overheated.
(2) It is impossible to make judgments on the resistors with internal failure or change in resistance value only by external observation. Use a multimeter to check. Do not use resistors whose resistance changes in general. ‘
- Resistors whose leads will be broken are most likely to cause noise and poor contact. When checking, shake the lead lightly by hand, it may be found loose. When measuring with the multimeter side, it may also be found that the resistance value pointed by the multimeter needle is unstable. After this type of resistor is found, it should be re-soldered.