the test method of the diode

1, detection of low-power crystal diode

A, identify positive and negative electrodes

(A) observe the symbol on the shell. Normally the diode is marked with a diode symbol, one end with a triangular arrow is positive and the other end is a negative pole.

(B) observe the color points on the shell. On the housing of the spot contact diodes, the polar color points (white or red) are usually marked. Generally marked with one end of the color point is positive. There are also diodes marked with color ring, with one end of the color ring is negative.

(C) to a smaller value of a measurement shall prevail, the black table is connected to one end of the positive pole, red pen then connected to the end of the negative.

B. Detects the highest reverse breakdown voltage. For AC power, because the ever-changing, so the highest reverse voltage is the diode to withstand the AC peak voltage.

2, detection of two-way trigger diode

Place the multimeter in the corresponding DC voltage block. The test voltage is provided by the megger. Test, shake the megger, million the same method to measure the VBR value. Finally, the comparison between VBO and VBR, the smaller the absolute difference between the two, indicating that the measured bidirectional trigger diode symmetry the better.

3, the detection of transient voltage suppression diode (TVS)

With a multimeter to measure the quality of the tube for a single pole of the TVS, according to the measurement of ordinary diode method, can be measured positive and reverse resistance, the general forward resistance of 4kΩ or so, the reverse resistance is infinite.

For the two-way polar TVS, any exchange red, black pen to measure the resistance between the two pins should be infinite, otherwise, that the pipe performance is bad or has been damaged. 4 high frequency variable resistance diode detection

Identification of positive and negative high-frequency varistor diodes and ordinary diodes in the appearance of the difference is the color of its color is different, ordinary diode color color is generally black, and high-frequency varistor diodes color color was light. Its polarity is similar to the ordinary diode, that is, with a green ring at one end of the negative, without a green ring at the end of the positive.

4, varactor diode detection

Will the multimeter red, black pen how to adjust the amount of varactor diode resistance between the two should be infinite. If the measurement, found that the multimeter pointer to the right there is a slight swing or resistance is zero, indicating that the measured varactor diode leakage failure or has been broken bad.

5, single-color light-emitting diode detection

In the multimeter to attach a special energy to 1.5V dry batteries, the multimeter set R × 10 or R × 100 block. This connection is equivalent to give the multimeter connected to the 1.5V voltage, the detection voltage increased to 3V (LED open voltage of 2V). When testing, use the multimeter two table pen to rotate the two pins of the LED. If the tube performance is good, there must be a normal light, this time, the black table pen is connected to the positive red pen is connected to the negative pole.

6, infrared light-emitting diode detection

A, identify the infrared light-emitting diode positive and negative electrodes. Infrared light two

The pole has two pins, usually the long pin is positive and the short pin is negative. Because the infrared light-emitting diode was transparent, so the shell of the electrode is clearly visible, the internal electrode is wider and larger one for the negative, and narrow and small one for the positive.

B, the first measurement of a red LED positive and negative resistance, usually the positive resistance should be about 30k, reverse resistance to 500k or more, so that the tube can be used normally.

7, infrared receiver diode detection

A, identify the polarity of the pin

(A) from the appearance of identification. Common infrared receiver diode appearance color is black. Recognize the pin when facing the receiving window, from left to right, respectively, for the positive and negative. In addition, there is a small chamfering plane at the top of the tube of the infrared receiving diode. The pin with the chamfering plane is usually negative and the other end is positive.

(B) first use a multimeter to determine the normal diode positive and negative electrode method to check, that is, exchange red and black pen two measuring tube resistance between the two pins, the normal, the resistance should be a large and a small. To the smaller value of a prevail, the red pen then the footsteps of the negative pole, the black pen then the pin is positive.

B, detection performance is good or bad. Measure the infrared receiver diode positive and reverse resistance with a multimeter electrical resistance. According to the size of the positive and reverse resistance, the infrared receiver diode can be judged to be good or bad.

8, the detection of laser diodes

In accordance with the detection of ordinary diode positive and reverse resistance method, you can laser diode pin order to determine the order. However, the detection should pay attention to, because the laser diode forward voltage drop than the ordinary diode to be large, so the detection of forward resistance, the multimeter pointer slightly slightly deflected only right.