Distinguishing the quality of crystal diodes 2

Polar tubes should be considered as the elders of the semiconductor device family. Long ago, people were fond of assembling a mineral radio to listen to radio broadcasts, which was later made into crystal diodes.

The most obvious property of a diode is its unidirectional conductivity, which means that current can only flow from one side but not from the other side (from the positive pole to the negative pole). We use a multimeter to measure the common 1N4001 silicon rectifier diode. When the red probe is connected to the negative terminal of the diode and the black probe is connected to the positive terminal of the diode, the probe will move, indicating that it can conduct electricity; Then connect the black probe to the negative terminal of the diode and the red probe to the positive terminal of the diode. At this point, if the multimeter needle does not move at all or only deviates slightly, it indicates poor conductivity. In the multimeter, the black probe is connected to the positive terminal of the internal battery

Several common diodes are shown in the figure. There are several types of packaging, including glass, plastic, and metal. Figure 2 is the circuit symbol of a diode, as its name suggests. A diode has two electrodes and is divided into positive and negative poles. The polarity is usually indicated on the outer shell of the diode. Most people use a ring of different colors to represent the negative electrode, and some directly mark it with a "-" sign. High power diodes are often packaged in metal and have a nut to secure them to the heat sink.