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Humidity Chamber and Optotrack Measurements

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  • Humidity Chamber and Optotrack Measurements

    Greetings to everyone,

    I have a two part question.

    PART 1: We are planning to buy or make a humidity chamber for material
    testing with a MTS or Instron test machine. We need a temperature controlled
    and humidity controlled test environment. The chamber would be approx. a 500
    mm cube with a supply of high humidity air at a temperature of 37C.

    We have information from MTS regarding their temperature controlled water
    bath and also spray nozzles to create a high humidity condition. The
    humidity supply is not under closed-loop control and the standard chamber
    size (250mm diameter cylinder) is not a suitable size.

    Does anyone have experience (or comments) regarding buying, making and/or
    using a humidity and temperature controlled test chamber. Are small scale
    commercial ones available or have people made their own (if at all)?

    PART 2. We will be using an Optotrack 3020 (active infrared markers)
    to record rigid body motion during testing in the above mentioned chamber.
    Therefore, a clear plastic? glass? barrier will be between the camera and
    the markers. We have not yet done a calibration check under these conditions
    and anticipate some kind of effect due to this barrier.

    The only similiar reference I have found is a paper by Lam et al.,
    (Calibration Characteristics of a Video Dimension
    Analyser (VDA) System, J Biomech 25(10):1227-1231 1992) which assessed the
    calibration of a 2D visible light measurement system with a 6.4mm thick,
    low-refractive index glass between the camera and specimen. They found
    changes in the calibration parameters with the glass and also by varying the
    angle of incidence.

    I would be happy to hear from anyone with experience using an Optotrack (or
    other active infrared system) with a clear sheet between the cameras and
    markers, or thoughts about distortion of 3D measurements, best type of
    material, etc.

    I will post a summary of responses.

    Thanks for your help.

    Darrell Goertzen

    M.E. M|ller Institute for Biomechanics
    University of Bern
    Murtenstrasse 35, P.O.Box 30
    CH-3010 Bern

    Tel: +41 (0)31 632 4976
    Fax: +41 (0)31 632 4951