Multimeter test method for ordinary light-emitting diodes:
The use of × 10kΩ block pointer multimeter can be roughly determine the good and bad light-emitting diodes. When normal, the diode forward resistance value of tens to 200kΩ, the value of the reverse resistance is ∝. If the forward resistance value of 0 or ∞, the reverse resistance value is very small or 0, it is easy to damage. Kind of detection methods, can not field to see the light-emitting situation of the light-emitting diode, because × 10kΩ block can not provide a large forward current to the LED.
With two multimeter with the measurement
If there are two pointer multimeter (* good with the same model) can be better to check the light-emitting diode light-emitting situation. Use a wire to connect the "+" terminal of one multimeter to the "-" terminal of the other. The remaining "-" pen connected to the positive pole of the measured light-emitting diode (P area), the remaining "+" pen connected to the negative pole of the measured light-emitting diode (N area). Two multimeter are set × 10Ω block. Under normal circumstances, the normal light can be connected. If the brightness is very low, or even do not emit light, the two multimeter are dialled to × 1Ω if, if still very dark, or even do not emit light, then the light-emitting diode performance is poor or damaged. It should be noted that you can not begin to measure the two multimeter placed in the × 1 Ω, so as not to overcurrent, damage to the light-emitting diode.
External auxiliary power supply measurement
With 3V regulated source or two series-connected dry cell and multimeter (pointer or digital can be) can be more accurate measurement of light-emitting diode light, electrical characteristics. To do this, connect the circuit as shown in Figure 10. If the measured VF between 1.4 ~ 3V, and the light-emitting brightness is normal, it can be said that the light-emitting normal. If the measured VF = 0 or VF ≈ 3V, and does not emit light, that the light-emitting tube is bad.
