A fixed resistor testing.
A two tables document (regardless of sign), respectively, at both ends of the pin contact resistance can be measured actual resistance value. In order to improve the measurement accuracy, the measured resistance should be based on the size of the nominal value to select the range. Since Ohm block scale nonlinear relationship, it's in the middle period of more sophisticated indexing should therefore be possible to make the value of the pointer indicates the scale of the fall in the middle position, that is, within the full-scale start of 20% to 80% range in radians, so more accurate measurement. According to a different level of resistance error. Are allowed between reading and nominal resistance has ± 5%, ± 10% or ± 20% of the errors. If not match, is out of tolerance, then the value of the resistance value.
B Note: When testing, particularly in the measure over tens of kΩ resistor values, the hands do not touch the conductive part of the table pen and resistance; the resistance welding down is detected from the circuit, at least to open a welding head, in order to avoid circuit Other elements produce test the impact, causing measurement error; color ring resistor color ring logo although able to be determined, but it is best to use a multimeter to test resistance at the time of its actual use.
2 cement resistance testing. Cement resistance detection methods and precautions and testing ordinary fixed resistors identical.
3 fuse resistors detection. In the circuit, when the fuse resistor fuse open, can make judgments based on experience: If it is found fuse resistors or charred black surface, it can be concluded that it overloaded by more than its current rating due to many times; If the surface without any trace of the open, it indicates that the current flowing through exactly equal to or slightly greater than its rated value fuse. For the surface without any trace of the fuse resistor to judge good or bad, can make use multimeter R × 1 block to measure, in order to ensure accurate measurement, should fuse resistors from one end of the circuit under the welding. If the measured resistance is infinite, then this fuse resistors has failed open, if the measured resistance falls far short of the nominal value, indicating that the resistance change value, should not be used again. Maintenance practices found that a small number of fuse resistors in the circuit is short-circuit breakdown phenomenon, attention should also be detected.
4 potentiometer test. Check the potentiometer, the first to turn the knob handle, and see whether the smooth rotation of rotary handle, switching is flexible, switch on, when off "clicks" Are crisp and listen potentiometer resistor internal contacts and friction sound, if "imperfections" sound, indicating poor quality. When tested with a multimeter first potentiometer resistance measured according to the size, choosing an appropriate multimeter resistance gear, then the following method can be detected.