LED positive and negative can be measured with a multimeter.
The output pulse current makes the pointer jitter for positive. Self-flash light-emitting diode inside the integrated circuit in the multimeter inside the role of 1.5V battery voltage began to oscillate, the output of the pulse current to make the pointer jitter, just because the voltage is too low to make the light-emitting diode light. But this phenomenon shows that the multimeter red and black pens are connected to the correct way, that is, the multimeter black pen is connected to the positive side of the flash light-emitting diode.
Note that in determining the positive and negative self-flash light-emitting diode, do not measure the ordinary diode, that resistance is small that measurement, the black pen is connected to the diode positive. Light-emitting diodes can efficiently convert electrical energy into light energy, in modern society has a wide range of uses, such as lighting, flat panel display, medical devices.
Light-emitting diode light-emitting principle
Diode is a semiconductor device in one of the most common devices, most semiconductors are most made from adulterated semiconductor materials (atoms and other substances) light-emitting diode conductor material is usually aluminum arsenide crop, in the pure aluminum arsenide crop, all the atoms are perfect and their neighbors Combined, leaving no free electrons connected to the current.
Light-emitting diodes, such as those used in digital display clocks, the size of the gap determines the frequency of the photons, in other words, the color of the light. When all diodes emit light, most are not very efficient. In a normal diode, the semiconductor material itself attracts a large amount of light energy and ends. A light emitting diode is covered by a plastic bulb concentrating light in a particular direction.
Refer to Baidu Encyclopedia-LED light-emitting diode for the above