Photodiode is a kind of detector that can convert light into electricity or signal. It is widely used in all walks of life in the world. However, there are many photodiodes on the market, and the quality of their use is far from reaching the standard that we use.

　　 Anyway, the quality problem of photodiodes is more serious. After we buy photodiodes, we can use methods to check them to make sure. Generally speaking, we start to detect the photodiode, usually the resistance file of the multimeter Rx1k can be used. At this time, when there is no light shining in the photosensitive diode, it actually looks like an ordinary diode, and it only has this unidirectional conductive effect. The data we detected should be the forward resistance of 8-9kΩ and the reverse resistance of more than 5MΩ.

　　 When we are testing, if we do not know the positive and negative poles of the photodiode, we can also use the general method of measuring the positive and negative poles of ordinary diodes to help ourselves determine. In other words, when measuring the positive resistance, the position where the black test lead is locked in the hand is the anode of the photodiode. At the same time, we can observe the deflection amplitude of the multimeter after irradiating the photodiode with light.