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LED General measurement
- Jul 31, 2017 -

Detection of ordinary light - emitting diodes

(1) with a multimeter. 

The use of a 10 × × block with a pointer multimeter can roughly determine the light and good diode is good or bad. Normally, the diode forward resistance is tens to 200kΩ, and the value of the reverse resistance is α. If the forward resistance value is 0 or ∞, the reverse resistance value is small or 0, it is easy to damage. This detection method, can not really see the luminous light tube, because × 10kΩ block can not provide a larger forward current to the LED.

If there are two pointer multimeter (preferably with the model) can better check the light emitting diode light situation. Use one wire to connect the "+" terminal of one of the multimeters to the "-" terminal of the other meter. The remaining "-" pen connected to the positive side of the LED (P area), the remaining "+" pen connected to the negative side of the measured tube (N area). Two multimeter are set × 10kΩ block. Under normal circumstances, after the normal light will be connected. If the brightness is very low, or even not light, you can dial two multimeters are to 1 mΩ if, if still dark, or even no light, then the light-emitting diode performance is bad or damaged. It should be noted that can not be measured at the beginning of the two multimeter will be placed in × 1mΩ, so as not to excessive current, damage to light-emitting diodes.

(2) external power measurement. 

With 3V regulator or two series of dry batteries and multimeter (pointer or digital can be) can be more accurate measurement of light-emitting diode light and electrical characteristics. For this reason, the circuit can be connected as shown in Fig. If the measured VF between 1.4 ~ 3V, and the luminous brightness of normal, can show normal light. If the measured VF = 0 or VF ≈ 3V, and no light, indicating that the LED is bad.

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