Detection of LED with Multimeter

Light-emitting diode (LED) is a kind of direct current is injected into the light emitting device, semiconductor crystal stimulated electronic from high level to low level recovery, emit the photons, which is commonly referred to as spontaneous emission transition. When the LED PN junction with forward bias, the injection of minority carriers and the majority carriers (electrons and holes) compound and light. It is worth noting that, for a large number of high-energy particles in their respective spontaneous emission in a row angular frequency v =Eg/h wave, but no fixed phase relationship between the columns of light, can have different polarization directions, and each particle emitted light along all possible directions, a process called spontaneous emission. The emission wavelength can be said to:

Lambda (m) =1.2396/Eg (eV)

Light-emitting diode (LED) by P GaAs, phosphide material. There is a junction inside it, also having a single conductivity, but the light emitting diode in the forward conduction will be light, the brightness of the light with the conduction current increased, a wavelength of light and color.

Ordinary light emitting diode multimeter detection method:

Multimeter R * 10K file measurement with 10K * Omega block pointer multimeter can largely determine the quality of light emitting diode. Normally, the diode forward resistance is ten to 200K, reverse resistance to /. If the forward resistance value is 0 or, the reverse resistance value is very small or is easy to be damaged. Kinds of detection methods, can not see the light of the light-emitting diode, because the X 10K block can not provide a larger forward current LED.

Two multimeter measuring if there are two pieces of pointer multimeter (preferably the same type) can check the luminous light emitting diode. Use a wire to connect the "+" terminal of one of the multimeter to the "-" terminal of the other table. The rest of the pen is connected to the positive electrode (P area) of the light emitting tube, and the remaining "+" pen is connected to the negative electrode of the light emitting diode (N). Two multimeter with x 10 ohm. Under normal circumstances, after the switch can be normal luminescence. If the brightness is very low, and even do not emit light, can be used to dial the two multimeter 1 x, if it is still dark, and even do not emit light, indicating that the light-emitting diode performance is bad or damaged. It should be noted that the two meter can not be measured at the beginning of the meter in the x 1, so as to avoid excessive current, damage led.

Dry battery external auxiliary power measurement series with 3V voltage source or two and a multimeter (pointer or digital can) can accurately measure the optical and electrical properties of light emitting diode. To this end, the circuit can be connected as shown in figure 10. If the measured VF between 1.4 ~ 3V, and the luminous brightness of normal, can be explained that the normal light. If the measured VF=0 is 3V or VF, and do not light, that light emitting tube has been bad.