Firstly, the output voltage of the resistance range of a pointer multimeter and a digital multimeter is different. Generally, the maximum output voltage of a pointer multimeter is 9 volts, while a digital multimeter generally has a maximum output voltage of 3 volts. At the same time, not only do they output different voltages, but we choose different ranges when measuring, and the output voltage of the resistance range of a digital multimeter varies from 1.0 volts to 3.0 volts, The resistance output voltage of a pointer multimeter is generally higher than that of a digital multimeter. The output voltage of a pointer multimeter is greater than the voltage drop value of the diode, and the diode can conduct. However, sometimes a digital multimeter is smaller than the voltage drop value of the diode, causing the diode to not conduct. This can cause infinite forward and reverse resistance values when measuring the diode.

Secondly, the voltage drop characteristics of the second stage transistor are different, which can also cause deviations in the results of measuring the second stage transistor using a pointer multimeter resistance level compared to using a digital multimeter to measure the second stage transistor. For example, silicon and germanium tubes generally have a voltage drop value between {{0}}.3 volts and 0.6 volts, but some more special second stage transistors, such as high-voltage diodes, have a larger conduction voltage drop and generally need to reach 0.7 volts or more, while our digital multimeter resistance level voltage is lower, It is not possible to conduct the diode, so it will cause the resistance value to appear infinite during measurement.

When measuring the quality of a diode with a digital multimeter, it is best to choose the diode gear. The diode gear of a digital multimeter is generally around 2.6 volts, which is generally greater than the forward voltage drop value of the diode, and the diode can conduct in both directions.