How to detect diodes

Last Update Time: 2018-12-03 14:00:20

1) the polarity discrimination of diodes

Observe the symbol marks on the shell. A symbol, usually marked with diodes, on a shell, with the end of a triangular arrow   is positive and the other is negative.

(2) observe the color dots on the shell. On the shell of a point-contact diode, there are usually polar dots (white or red) and a positive pole at one end. There are also diodes marked with colored rings, one end of which is negative.

(3) observe the contact needle in the glass shell. For point-contact diodes, if the markings are blurred, the black or white paint layer on the shell can be slightly scraped off, and the internal structure of the diode can be observed through glass, with a positive electrode at one end of the metal touch pin. One end of the semiconductor chip is a negative pole.

4)Observe the length of the pin. For light-emitting diodes, the pin length is positive and the pin short is negative.

5) to measure and discriminate with multimeter. Put the pointer multimeter in the RX1kQ block, first use the red and black meter pen arbitrary measurement the resistance between the two ends of the diode, and then exchange the meter pen to measure the number of times. If the pole tube is good, the difference between the two measurements is very big, in which the black meter pen is connected with a positive pole, and the red meter pen is connected with a negative plate.

2) judging the quality of two-plate tube

To judge the quality of two-plate tube, the common method is to test the positive and reverse resistance of the pole tube, and then judge it. The smaller the forward resistance, the better the reverse resistance, the greater the difference between the two. The general forward resistance is hundreds of euros or hundreds of kilos. The reverse resistance is several hundred megabyors or infinity, and such diodes are good. If both forward and reverse resistances are infinite, they represent internal breakage. If the forward and reverse resistance are zero, then the PN junction breakdown or short circuit, indicating that the second straight tube is bad. If the positive and reverse resistance is the same, the diode is also bad.

5. Selection of diodes

When selecting diodes, different types and characteristics of pole tubes are generally selected according to the requirements of specific circuits. The detector diode should be used in the test circuit, the voltage regulator tube should be used in the voltage regulator circuit, and the switch diode should be used in the rectifier circuit. It is also necessary to pay attention to the difference between the parameters and characteristics of different types of diodes.

If you want to know more, our website has a product specification for diodes, you can go to ALLICDATA ELECTRONICS LIMITED to get more information