The actua l resistance value can be measured by connecting the two surface pens (no matter positive or negative) to the pins at both ends of the resistance.
In order to improve the measurement accuracy, the range should be selected according to the nominal value of measured resistance.Because of the non-linear relation of the ohmstop scale, the middle part of the scale is more fine.
Therefore, the pointer indicator should be located at the middle part of the scale as much as possible, that is, within the range of 20%-80% radians of the full scale start, so as to make the measurement more accurate.Different levels of resistance error.
An error of plus or minus 5%, plus or minus 10%, or plus or minus 20% was allowed between readings and nominal resistance values.If not, beyond the error range, the resistance value is changed.
Note: test, especially in more than dozens of k Ω measuring the resistance of the resistance, hand don't touch the pens and and resistance of the conductive part;
When the resistance being tested is soldered down from the circuit, at least one head should be soldered to prevent other elements in the circuit from influencing the test and causing measurement error.
Although the resistance value of the color ring resistance can be determined by the color ring logo, it is better to test the actual resistance value with a multimeter.
Testing of cement resistance.The method and notice of testing cement resistance are identical with that of testing ordinary fixed resistance.
Detection of fused resistor.In the circuit, when the circuit is opened by the fusing resistor, it can be judged according to experience: if it is found that the surface of the fusing resistor is black or burnt, it can be determined that the excessive load is caused by the electric current passing through it exceeding many times the rating value;
If the surface is open without any trace, the current passing through is just equal to or slightly greater than its rated fuse value.
For the judgment of the quality of the fuse resistor without any trace on the surface, it can be measured by means of the universal meter R x 1. In order to ensure the accuracy of measurement, one end of the fuse resistor should be welded from the circuit.
If the measured resistance value is infinite, this circuit breaker has failed. If the measured resistance value is far from the nominal value, it indicates that the resistance value should not be used again.
In the maintenance practice, it is found that there are a few fusing resistors in the circuit are broken short circuit phenomenon, and attention should be paid to the detection.
Potentiometer detection.When checking the potentiometer, the first thing to do is to turn the handle to see whether the handle rotation is smooth, whether the switch is flexible, whether the "click" sound is crisp when the switch is on or off, and listen to the sound of the contact point and resistance body friction in the potentiometer.
When testing with a multimeter, the appropriate resistance of the multimeter should be selected according to the resistance value of the potentiometer, and then the following method can be used for testing.