Although this can not suppose a great problem in the devices of measurement with an ample angle of view, the superiors to forty degrees or more, for the angle devices Straits, the differences in the readings can be considerable. (It is possible to indicate that IT BACKS WATER (Internationale Commission of l" Eclairage) the recommendation is to use the mechanical axis of the LED instead of the optical axis like measurement reference) – the measurement of the yield in a certain time interval or when it became stabilized finally. When the LED receives the first current, the temperature of the union is increased due to the consumed electric power. (The temperature of the union of the LED is determined by Tj = Ta + (* If Vf) * Rth (ja)), and it can take several seconds or several minutes before the exit of light has reached the heat balance and a stable value. A diminution in the 5-20% production or is not infrequent more.

Often it is not practical to wait for lengths periods of time between the accomplishment of the tests in the LED, reason why approximately settles down like standard an interval of five seconds like an acceptable limit in the traction of the stabilization. – To assure that the room temperature is constant during the test. The LED usually changes of brightness and color with the temperature. As it increases the temperature, it diminishes the production and the changes of color towards the least upper bound of the phantom. – To always use a current source direct voltage plateau (Vf). – To use a configuration of easily reproducible test. Felipe Garci’a is consulting of Ibertest the International Testing of material and Traction original Author and source of the article