Resistors play a vital role in circuits, and the stability of their performance is directly related to the normal operation of the entire circuit system. Therefore, mastering the detection method of resistors is crucial to ensure the reliability of the circuit. Detection methods vary depending on the type of resistor. The detection methods for fixed resistors and fused resistors will be introduced in detail below.
1. Detection of fixed resistors
When testing a fixed resistor, you first need to connect the two test leads of the multimeter (no need to distinguish between positive and negative) to the two pins of the resistor, so that the actual value of the resistance can be measured. In order to improve the accuracy of the measurement, the range should be selected to match the nominal value of the resistance being measured. Due to the non-linear characteristics of the ohm scale, the best measurement range is the 20% to 80% area in the middle of the scale, which ensures the accuracy of the reading. Depending on the resistance error level, the allowable error range is usually ±5%, ±10% or ±20%. Readings outside of this range may indicate a change in resistor value.
When testing, you should pay attention to the following points: Especially when measuring a resistance value of tens of kΩ or more, avoid direct contact with the test leads and the conductive parts of the resistor with your hands; before testing, the resistor should be soldered off the circuit or Solder open at least one end to avoid interference from other components in the circuit, which could cause measurement errors. In addition, although the resistance value of the color ring resistor can be determined by the color ring mark, it is best to use a multimeter to conduct the actual resistance test before use.
2. Detection of blown resistors
In a circuit, when an open circuit occurs in a fuse resistor, a preliminary judgment can be made based on its appearance. If the surface of a fused resistor appears blackened or scorched, it usually means that it is overloaded and the current flowing through the resistor is much higher than the rated value. If there are no obvious traces on the surface of the fuse resistor but an open circuit occurs, this may indicate that the current passing through is just equal to or slightly greater than its rated fuse value.
For fuse resistors with no traces on the surface, you can use the R×1 block of a multimeter to detect them. To ensure accurate measurements, one end of the resistor should be soldered off the circuit. If the measured resistance value is infinite, it means that the fuse resistor has been opened and failed; if the measured resistance value is very different from the nominal value, the resistor has changed value and should not be used anymore. In maintenance practice, attention should also be paid to detecting whether any fuse resistors are broken down and short-circuited in the circuit.
Through the above detection method, the performance of the resistor can be effectively evaluated to ensure the stable operation of the circuit system. Especially in complex or high-precision circuit designs, accurate detection of resistors is particularly critical, helping to promptly detect and solve potential circuit problems.