How to detect the winding resistor?
First, the detection of fuse resistors
Once the fuse resistor is blown out, the surface of which is burned or black, and the fuse resistor in this phenomenon does not need to be detected, it can be determined that it is damaged. For the determination of the fuse resistor of the surface without any traces, the multimeter can be detected.
A section of the fuse resistor is welded from the circuit, and the resistance value is measured using the multimeter R × 1 gear. If the measurement resistance is infinite, then this fuse resistor has failed to open;
Second, the detection of fixed resistors
Using a multimeter, select the measured range according to the size of the measured electrical resistance, and the actual resistance values ??can be measured by the two ends of the resistor, respectively. Then, if the error is allowed to allow the error to be compared, the resistor has changed value if the error range is exceeded.
Note: When testing, the measured resistor should be sold from the circuit, at least one segment is to be welded, so as to avoid the impact on the test in the circuit; test the resistor of tens of thousands of obloids, hands do not touch The conductive portion of the form pen and the resistor may result in an error.
Third, the detection of potentiometers
1. Experience testing
The empirical test is to judge by the observation of the potentiometer appearance and manual experiment. The normal potentiometer should have no abnormalities, discoloration, etc. Otherwise, the potentiometer is not normal.
2, the multimeter test method is tested with the multimeter test, according to the size of the measured potential resistance, the appropriate resistance gear is selected, mainly for two aspects of testing.
Fourth, the detection of cement resistors
The cement resistor is actually one of the fixed resistors, but the structure is more complicated than normal fixed resistors. Its detection methods and precautions are identical to the test normal fixed resistors.
V. Testing of photosensitive resistors
1, light transmission detection
In the light transmissive state, use the multimeter to contact the two scales of the photosensitive resistor. If the multimeter pointer has a larger swing, the resistance is significantly reduced, the smaller this value, the better the performance of the photosensitive resistor. If this value is large or infinite, it means that the inside of the photoresistor is damaged inside, cannot be used.
2, prototype detection
Use a black sheet to cover the light-transmissive exposure of the photosensitive resistor, use a meter to measure the resistance value, at this time, the pointer of the multimeter should be substantially different, the resistance should be large or close to infinity, the greater this value, and the photosensitive The better resistance performance. If this value is small or close to zero, the photosensitive resistor is damaged and cannot be used.
3, intermittent light receiving detection method
The light-transmissive window of the photosensor is aligned with the incident light, shake with a small black sheet on the window of the photosensitive resistor, so that it is disconnected, if the multimeter pointer swings with the shake of the black sheet, explain the photosensitive resistance The photosensitive properties of the unit are normal. If the multimeter pointer clock stops in a certain location, it is not swing with the shaking of the black tab, indicating that the performance of the photosensor has become inferior and cannot be used.