How to see the positive and negative signs of a universal SMD diode?

     When using universal SMD diodes, pay attention to the positive and negative poles of the diode. After the positive and negative poles are reversed, the finished sample or product may not work. If a diode is used for rectification, it will be caused by incorrect polarity. Burning an entire board or product has serious consequences. To avoid such consequences, you must understand how to check the positive and negative signs of an SMD diode!

       First download the physical identification scheme of the universal SMD diode:

• The side with 4 horizontal lines in the red area above is negative and the other side is positive; different manufacturers of universal SMD diodes also have different logos. The picture above is a horizontal line, there are two horizontal lines, and some are a white rectangle. But no matter what kind of logo it is, let's summarize one thing: the negative side has a clear logo, and the positive side has no silkscreen for identification.

  In addition to distinguishing SMD diodes by identification, there is another way to more accurately distinguish between positive and negative poles, that is, use a multimeter to distinguish between the positive and negative poles of an SMD diode:

       Multimeters are divided into pointer and digital. With the development of electronic technology, pointer multimeters are now rarely used, so how to check digital multimeters:

      Set the multimeter to diode position, place test leads on both sides of the SMD diode, and then look at the value on the display screen:

1. The screen displays 1. This means the resistance is infinite, the black test pen is the negative pole and the red test pen is the positive pole;
2. The screen shows about 0.600, the value is displayed, and the multimeter beeps: the red test pencil is the negative electrode and the black test pencil is the positive electrode;
3. Of course, there is a third situation, that is, regardless of how the test leads are placed, the displayed value on the screen is close to 0, and the multimeter emits a sound, which indicates a breakdown of the SMD diode. broken, broken and can no longer be used.

 With the above method of distinguishing the positive and negative poles of an SMD diode, we can understand that there are disadvantages in distinguishing the external identification of an SMD diode. The best way is to use a multimeter to check the difference. If you produce products in batches, then, of course, it is impossible to test each SMD diode once! To avoid this problem, when buying materials for universal SMD diodes, you need to pay attention to the choice of quality manufacturers who have been engaged in the production of SMD diodes for a long time.