S025 Orientation Test

Viso Systems Forums Light Inspector software Questions S025 Orientation Test

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    I have just downloaded version 5.88 of the Light Inspector software and am interested in the orientation testing function.

    In your opinion do you think the capability supplied by the software is enough to satisfy the S025 specification? Namely that the device under test must be tested in its operating orientation, or else a correction factor must be applied. I personally think the method suggested by the software (warming up the test device in its operating position, then quickly swapping to its test position and measuring the intensity change) would give a good idea of a correction factor that could be applied to the test in post processing, however it does not account for factors such as cooling due to airflow over the test device when moving from its operating position to its test position. Whether or not this causes any discernible difference to the comparison I’m not sure.

    Otherwise do you have any suggestions relating to satisfying the orientation requirements of S025? We test with a LabSpion.

    Thank you.


    According to CIE S 025/E:2015 (Test Method for LED lamps, LED luminaires and LED Modules), the light source shall remain in its designed operating condition throughout the stabilization and testing period. If this requirement is not met, the measurements shall be corrected to the performance in the designed operating position.

    Many LED lighting fixtures are intended to emit light primarily upward or downward, whereas the burning position in Viso goniometers is horizontal. Hence, Viso offers a systematic approach to make such corrections.

    The CIE standard advices to use an auxiliary photometer to measure the light source in both positions. Viso of course wishes to use the excellent photometer already in place. We believe that moving the light source fast (< 20 sec) from burning position to measuring position will not affect the output significantly - neither in terms of incurred airflow, nor in terms of changing internal temperature conditions. Naturally, we imply that the light source should be warmed up in the laboratory in close vicinity to the C-plane head so that all conditions except the burning position stay unaltered.

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