Electronic multimeter to measure LED turn signal current
How to measure the LED turn signal current with an electronic multimeter? Use a multimeter to detect the current of ordinary light-emitting diodes. Three measurement methods are provided: use the R×10K range of the multimeter to measure, use two multimeters to measure together, and connect an external auxiliary power supply to measure.
Due to the characteristics of the LED lamp, the lighting current should be low-voltage DC, so the digital multimeter should be turned to the DC current block, 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 in series to the break. After the power is turned on, the LED light is lit. 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 is 1 milliamp (equal to 1000 microamps), and the number of LED lights is 100, then 1000÷100=10 (microamperes), that is, the current passing through each LED light is 10 microamps. Give it a try. (Please pay attention to safety, the voltage before rectification is 220v)
A light-emitting diode (LED) is a light-emitting device that directly injects current. It is the result of photons being emitted when excited electrons inside the semiconductor crystal return from a high energy level to a low energy level. This is commonly known as a spontaneous emission transition. When the LED When the PN junction is forward biased, 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, they spontaneously emit a column of angular frequencies. It is a light wave with ν =Eg/h, but there is no fixed phase relationship between the light waves in each column. They can have different polarization directions, and the light emitted by each particle propagates in 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 emits light when it is forward-conducted. The brightness of the light increases as the conduction current increases, and the color of the light is related to the wavelength.
Multimeter detection method for ordinary light-emitting diodes:
1. Use the R×10K range of the multimeter to measure
The quality of the light-emitting diode can be roughly judged by using a pointer multimeter with a ×10kΩ block. 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 very small or 0, it is easily damaged. With this detection method, the lighting condition of the luminous tube cannot be seen in person, because the ×10kΩ block cannot provide a large forward current to the LED.
2. Use two multimeters to measure together.
If you have two pointer multimeters (preferably the same model), you can better check the lighting conditions of the light-emitting diodes.
Use a wire to connect the "+" terminal of one multimeter to the "-" terminal of the other meter.
The remaining "-" pen is connected to the positive electrode (P area) of the luminous tube under test, and the remaining "+" pen is connected to the negative electrode (N area) of the luminous tube under test. Both multimeters are equipped with ×10Ω block.
Under normal circumstances, it will light up normally after being turned on. If the brightness is very low or even does not emit light, you can dial both multimeters to ×1Ω. If it is still very dark or even does not emit light, it means that the LED has poor performance or is damaged.
Note that you cannot set the two multimeters to ×1Ω at the beginning of the measurement to avoid excessive current and damage to the light-emitting diodes.
3. External auxiliary power supply measurement
The optical and electrical characteristics of the light-emitting diode can be measured more accurately with a 3V regulated source or two dry batteries connected in series and a multimeter (either analog or digital).
