First, the detection method and experience of the resistor
Detection of fixed resistors.
The actual resistance value can be measured by connecting the two test leads (not positive or negative) to the two ends of the resistor. In order to improve the measurement accuracy, the range should be selected according to the nominal value of the measured resistance. Due to the non-linear relationship of the ohmic scale, its middle section is finer. Therefore, the pointer indication value should fall as far as possible to the middle position of the scale, that is, within the range of 20%~80% radians of the full scale, so that The measurement is more accurate. Depending on the level of resistance error. Errors of ±5%, ±10%, or ±20% are allowed between the reading and the nominal resistance, respectively. If it does not match, if the error range is exceeded, the resistance value is changed.
Detection of the fuse resistor. In the circuit, when the fuse resistor is melted and disconnected, it can be judged according to experience: if the surface of the fuse resistor is found to be black or burnt, it can be concluded that its load is too heavy, and the current passing through it exceeds the rated value many times; If the surface is open without any traces, it means that the current flowing is exactly equal to or the pin is greater than its rated blown value. Judging whether the fuse resistor has no trace on the surface can be measured by the multimeter R×1 block. To ensure accurate measurement, one end of the fuse resistor should be soldered from the circuit. If the measured resistance is infinite, it means that the fuse resistor has failed open circuit. If the measured resistance value is far from the nominal value, it indicates that the resistance value is not suitable for reuse. In the maintenance practice, it is found that there are also a few blown resistors that are short-circuited in the circuit, and attention should be paid when testing.
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