Microfading Tester International Discussion Group

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  • 1.  Setting the current for the 3000K LED using the Instytut Fotonowy MFT

    Posted 20 days ago

    Hello MFT community,

    I am wanting to shorten the test duration for a sample by increasing the current. Following the Getty protocol for plotting the calibration data in excel, the maximum current within the linear range is 800mA. Is there any danger or risks that I need to consider if I decide to set the current to a higher level than the linear range - say 900 or 950mA. Would this affect the reliability of the ageing data?

    For context, we are trying to see how long it will take for a sample to reach a certain DE in the test, but also don't want each test run to be 1.5 hours long.

    Any advice that you can provide would be appreciated.

    Thanks,

    Noni



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    Noni Zachri
    Paper and Photographs Conservator
    Grimwade Conservation Services
    North Melbourne
    Australia
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  • 2.  RE: Setting the current for the 3000K LED using the Instytut Fotonowy MFT

    Posted 16 days ago

    Dear Noni,

    I think it's OK to use a higher current of 900 or 950 mA to elevate the power of your light source. The obvious consequence is that it will fade faster, which is what you want!

    In terms of using a current value that is less linear than the range of values from ~400-800 mA, this might impact potential modeling of the results. If we stay within the more linear range, one might assume that an increase in current will produce a predictable increase in power and, presumably, a predictable change in color.

    Have any other Fotonowy users employed currents of 900 mA in testing?



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    Vincent Laudato Beltran
    Scientist, Getty Conservation Institute
    Chair, MFT-IDG
    vbeltran@getty.edu
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  • 3.  RE: Setting the current for the 3000K LED using the Instytut Fotonowy MFT

    Posted 14 days ago
    Hello Noni,
    I routinely use a current of 900 mA (automated MFT form Iinstytut Fotonowy). The light output calibration is performed up to 950 mA, so I don't have to rely on data extrapolation. Using a higher current shortens the measurement time. I usually use a dose of 2 Mlxh as the criterion for the end of the measurement, and at 900 mA for a CT=5500K LED, it takes in my case just 10 minutes.
    Best,
    Tomasz


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    Tomasz Łojewski, PhD
    Faculty of Materials Science and Ceramics 
    AGH University of Krakow, Poland
    home.agh.edu.pl/~lojewski