Three Important Precautions for Measuring Variable Resistors with a Multimeter
There are many issues that need to be paid attention to when using adjustable resistor products, such as when using a multimeter to measure adjustable resistors. Here are three precautions for measuring adjustable resistance with a multimeter, as follows:
Note 1: The measuring range should be determined based on the measured resistance value, so that the pointer indicates the middle section of the scale line for easy observation;
Note 2: Do not touch the two ends of the resistor or the metal part of the probe when inspecting the heating element resistor. Otherwise, it may cause testing errors;
Note 3: After confirming the range of the resistance range through inspection, we need to perform zero adjustment. The method is to short-circuit the two probes (directly touch each other), adjust the "zero adjustment" device so that the pointer accurately points to the "0" on the Ω scale line, and then measure the resistance value of the resistor.
Test the quality of diodes, transistors, and voltage regulators on the road:
Because in practical circuits, the bias resistance of transistors or the peripheral resistance of diodes and voltage regulators are generally large, mostly in the hundreds or thousands of ohms range. Therefore, we can use the R × 10 Ω or R × 1 Ω range of a multimeter to measure the quality of the PN junction in the circuit. When measuring on the road, the PN junction should have obvious forward and reverse characteristics when measured in the R × 10 Ω range (if the difference in forward and reverse resistance is not significant, the R × 1 Ω range can be used for measurement). Generally, the forward resistance should indicate around 200 Ω when measured in the R × 10 Ω range, and around 30 Ω when measured in the R × 1 Ω range (there may be slight differences depending on different phenotypes). If the measurement result shows that the forward resistance is too high or the reverse resistance is too low, it indicates that there is a problem with the PN junction, and the tube is also problematic. This method is particularly effective for maintenance, as it can quickly identify faulty pipes and even detect pipes that are not completely broken but have deteriorated characteristics. For example, when you measure the forward resistance of a PN junction with a low resistance range and it is too high, if you solder it down and measure it again with the commonly used R × 1k Ω range, it may still be normal. In fact, the characteristics of this tube have deteriorated and it cannot work properly or is unstable.
