The paper’s purpose is to describe and discuss the study of LED diodes, measured with the help of the TERALED system. A short description of the measurement system is given. Four batches of 5 mm LEDs and two batches of PowerLED diodes are measured and the comments and discussion of the measured results are given. The experiments show clearly that some manufacturer’s LEDs do not match the parameters given in the datasheet. The reasons are not clear, but it seems to us that the problems of degradation of the construction materials of LEDs are not connected with the degradation of the semiconductor material itself.
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