Electronic multimeter to measure the current of led turn signal (ordinary light emitting diode)
How to measure the current of LED turn signal with electronic multimeter
Due to the characteristics of LED lamps, the lighting current should be low-voltage direct current, so the gear of the digital multimeter should be set to the DC current position, and then find the rectified DC input on the LED lamp board, disconnect it, and then turn the digital The test leads of the multimeter are connected to the fracture in series, and the LED lights are lit after the power is turned on. At this time, the current displayed by the multimeter is the total flow. Divide the total flow by the number of LED lights to get the current value of each LED light. For example : The total flow rate is 1 mA (equal to 1000 microamps), and the number of LED lights is 100, then 1000÷100=10 (microamperes), that is, the current passed by each LED light is 10 microamperes. Try it out. (Please pay attention to safety, the voltage is 220v before rectification)
A light-emitting diode (LED) is a light-emitting device that directly injects current. It is the result of emitting photons when the excited electrons in the semiconductor crystal return from a high energy level to a low energy level. This is commonly referred to as a spontaneous emission transition. When the LED The PN junction is applied with a forward bias, and the injected minority carriers and majority carriers (electrons and holes) recombine and emit light. It is worth noting that for a large number of particles at high energy levels, each spontaneously emits a row of angular frequencies It is the light wave of ν = Eg/h, but there is no fixed phase relationship between the columns of light waves, and there can be different polarization directions, and the light emitted by each particle propagates along all possible directions. This process is called spontaneous emission. Its emission wavelength can be expressed by the following formula: λ(μm)=1.2396/Eg(eV)
Light-emitting diodes (LEDs) are generally made of materials such as gallium arsenide phosphide and gallium phosphide. There is a PN junction inside it, which also has unidirectional conductivity, but the light-emitting diode will emit light when it is conducting forward, and the brightness of the light will increase with the increase of the conduction current, and the color of the light is related to the wavelength.
Multimeter detection method for ordinary light-emitting diodes:
1. Use the R×10K file of the multimeter to measure
Using a pointer multimeter with a ×10kΩ block can roughly judge whether the light-emitting diode is good or bad. Normally, the forward resistance of the diode is tens to 200kΩ, and the reverse resistance is ∝. If the forward resistance value is 0 or ∞, and the reverse resistance value is small or 0, it is easy to be damaged. With this detection method, the luminescence of the luminescent tube cannot be seen on the spot, because the ×10kΩ block cannot provide a large forward current to the LED.
2. Use two multimeters to measure
If you have two pointer multimeters (preferably the same model), you can better check the light-emitting diodes.
Connect a wire from the "+" post of one of the multimeters to the "-" post of the other meter.
The remaining "-" pens are connected to the positive electrode (P area) of the luminous tube under test, and the remaining "+" pens are connected to the negative electrode (N area) of the luminous tube under test. Both multimeters are set to ×10Ω block.
Under normal circumstances, it can emit light normally after being connected. If the brightness is very low or even does not emit light, both multimeters can be dialed to × 1Ω. If it is still very dark or even does not emit light, it means that the performance of the light-emitting diode is poor or damaged.
Note that the two multimeters cannot be placed in ×1Ω at the beginning of the measurement, so as to avoid excessive current and damage the light-emitting diodes.
3. External auxiliary power measurement
The optical and electrical characteristics of light-emitting diodes can be measured more accurately with a 3V regulated source or two dry batteries in series and a multimeter (either pointer or digital).
