The FMVSS humidity test, as described in 571.108 S8.7, for forward automotive lamps permits environmental conditions to vary within a given tolerance. Pre-soak conditions of the lamp for the test may vary. The tolerances during the soak portion of the test allow for a + 4 degree C variation (from the initial 38 degree C environment) and a + 10 % variation from the initial 90 % environment relative humidity. Tolerances during the wind portion of the test allow for a + 40 C variation (from the initial 23 degree C environment), a + 10 % variation from the initial 30 % environment relative humidity, and a - 0.153 m/s (- 30 ft/min) variation from the initial 1.68 m/s (330 ft/min) airspeed setting. Utilizing a climate control wind tunnel, this study demonstrates that the tolerances on the environmental test conditions will produce substantial test result variation. The discussion emphasizes the best environmental condition to minimize time to clear condensation for a particular automotive lamp. The moisture clearing time requirements, such as FMVSS Humidity test can produce widely varying test results for any lamp. lt is common to retest a lamp to the FMVSS requirement until it passes. The variables that effect clearing time have been identified and quantified. Within the tolerance of the FMVSS Humidity test the moisture concentration within the lamp can vary by a factor of 1.905, which leads to varying water droplet sizes. This in turn can vary evaporation time by a factor of 1.537. The humidity during the WIND portion of the test will effect clearing time by another factor of 1.167. Taking these three effects into account compares well with test results. Finally, cleanliness of the lamp surfaces will vary the amount of condensation and size of condensation droplets. To improve consistency when testing to the FMVSS Humidity requirement, the following is recommended. Precondition the lamps in a controlled low humidity environment before starting the SOAK portion of the test. Maintain tighter tolerance and consistent settings on temperature and humidity levels during the test. Use of sensor instrumentation to monitor test conditions will provide understanding of results. Always use a clean lamp sample to reduce condensation formation on the inside surface of the lens.


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    Title :

    The effect of environmental conditions on moisture clearing time in automotive lamps


    Additional title:

    Die Einflüsse von Umweltbedingungen auf Feuchtigkeitsabklingzeiten in Automobillampen


    Contributors:
    Bielecki, J.W. (author) / Chang, M. (author) / Poorman, T. (author)


    Publication date :

    2003


    Size :

    5 Seiten, 2 Bilder, 2 Tabellen, 8 Quellen




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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