Introduction to Measuring Light-Emitting Diodes (LEDs) with a Multimeter
The forward voltage drop of infrared light-emitting diodes is generally 1.3-2.5V, and the forward and reverse resistance of infrared light-emitting diodes can be measured using a pointer multimeter with R × 10k settings. Normally, the forward resistance value is about 15~40k Ω (the smaller the value, the better); The reverse resistance is greater than 500k Ω. If both the forward and reverse resistance values are measured to be close to zero, it indicates that the infrared light-emitting diode has been internally broken down and damaged. If both the forward and reverse resistance values are measured to be infinite, it indicates that the diode has been opened and damaged. If the measured reverse resistance value is much less than 500k Ω, it indicates that the diode has been damaged due to leakage.
Due to the infrared light emitted by infrared light-emitting diodes, it is not visible to the human eye. In addition to using the above method to determine the quality of the PN junction, a photosensitive device (such as a 2CR or 2DR silicon photovoltaic cell) can be prepared as a receiver, and a multimeter can be used to measure the voltage changes at both ends of the photovoltaic cell. To determine whether the infrared light-emitting diode emits infrared light when subjected to an appropriate forward current.
Visual inspection method to determine the positive and negative electrodes of light-emitting diodes (applicable to infrared light-emitting diodes and ordinary light-emitting diodes packaged in transparent resin)
LEDs have two pins, usually the long pin is the positive pole and the short pin is the negative pole. Infrared light-emitting diodes and transparent packaged ordinary light-emitting diodes have clear and visible electrodes inside their shells. The wider and larger electrode inside is the negative electrode, while the narrower and smaller electrode is the positive electrode.
