Identification and detection of crystal diodes 2

(3) Maximum reverse current/RM. Maximum reverse PIC16LF84A-04I/SS.html" target="_blank" title="PIC16LF84A-04I/SS">PIC16LF84A-04I/SS The current is the reverse current at the maximum reverse operating voltage, and the smaller this value, the better the unidirectional conductivity of the diode.

3. Detection of ordinary diodes

Commonly used crystal diodes include 2AP, 2CP, 2CZ, and 1N4000 series.

Generally, diodes have polarity markings on the casing. If there are no markings, the polarity of the diode can be determined by its small forward resistance and large reverse resistance, and this characteristic can also be used to detect the quality of the diode.

(1) Performance discrimination. The testing method is that the greater the difference between the forward and reverse resistance values of the crystal diode, the better. The greater the difference between the two, the better the unidirectional conductivity of the diode. If the forward and reverse resistance values of the diode are very similar, it indicates that the tube is broken. If both the forward and reverse resistances are small or zero, it indicates that the tube has been broken down and the two electrodes have short circuited; If both the forward and reverse resistances are high, it indicates that there is an open circuit inside the tube and it cannot be used.

(2) Polarity discrimination. When testing the forward and reverse resistance, when the measured resistance value is small, the electrode connected to the black probe is the positive terminal of the diode, and the electrode connected to the red probe is the negative terminal of the diode.

The forward and reverse resistance values of the diode are significantly different from the range (R × 100, R × lk) selected for the multimeter ohm range, which is a normal phenomenon.

4. Detection of light-emitting diodes

(1) Discrimination of positive and negative polarity. Most light-emitting diodes are transparent or semi transparent. By observing the size of the two metal plates inside the light-emitting diode, the polarity of the diode can also be determined. Usually, the larger end of the metal sheet is the negative electrode, and the smaller end of the metal sheet is the positive electrode. If the LED is new, it can be judged by the length of the pins, that is, the long pin is the positive pole and the short pin is the negative pole.diode