How to measure the diode correctly?

Diode is an electronic device made of semiconductor materials. Its main materials are silicon, selenium, germanium, etc., which have unidirectional conductivity. How to measure the diode correctly?

Generally, the pin polarity of diode can be identified according to the identification information, as shown in the figure. It can also be judged by multimeter.

The fabrication materials of diodes can be divided into germanium semiconductor materials and silicon semiconductor materials. It is also critical to accurately distinguish the fabrication materials of diodes when selecting and replacing diodes. When measuring the diode with a digital multimeter, the actual measurement is the forward voltage of the diode, while the pointer multimeter measures the forward and reverse resistance of the diode. Be sure to pay attention to this difference.

Use a digital multimeter to test the diode. First, insert the red probe into the "V Ω" jack. The polarity of the probe is "+". Insert the black probe into the "COM" jack. The polarity of the probe is "-". Adjust the range knob of the multimeter, and set the gear of the digital multimeter to the "diode" gear. Put the red and black probes on the two pins of the diode at random. When the multimeter screen displays within the range of 0.5~0.7V, it indicates that the diode is positively conducting, indicating that the diode is a silicon diode. At this time, the red probe is connected to the anode of the diode, and the black probe is connected to the cathode of the diode, as shown in the above figure. When the multimeter screen displays "1", it indicates that the measured diode is reverse biased. If the measured positive conduction voltage of diode is 0.2~0.3V, it means that the diode is germanium diode, and the pin identification is the same as that of silicon tube. If the forward and reverse voltages are infinite or both are zero (the buzzer sounds) or close, it means that the diode has an open circuit or a short circuit or its performance has deteriorated.