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friction of a pen on a digitizer tablet

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  • friction of a pen on a digitizer tablet

    Dear BIOMCH-Ls,

    Maybe because I posted my question on 'Veterans-day' , until now I have
    received only one reaction. I will give it a second try with extra
    information added.

    I have a question concerning the friction of a pen on a digitizer tablet
    (Calcomp 9000). In an experiment where subjects had to make a precise
    single fast movement
    from one point to the other, axial pen pressure and velocity were measured.
    A secondary, cognitive load, condition was included. Motor preparation and
    motor performance of 2 groups
    were investigated.

    We measured the development of mean axial pen pressure during 3 phases:
    holding the pen still on the tablet (P1) - reaction (P2) - actual movement (P3)
    The first number between the parenthesis is the condition without cognitive
    load, the 2nd number is the condition with load

    GRP1: P1(117;131) / P2(129;149) / P3(142;158)
    GRP2: P1(118;113) / P2(139;134) / P3(183;199)

    Both groups reacted in 'P3' on the cognitive load with a +- 15 gram raise.
    GRP1 raised pen pressure from 142 to 158 grams, GRP2 from 183 to 199
    Both groups performed the task at comparable speed. RTs were higher in GRP2

    My question: Is the force increase needed to move the pen along the
    trajectory equal for both groups? My hunch is (but that is not scientific)
    that GRP2 will need disproportionate more force input -1- because of
    the tablets' elastic properties, the tablet will spring back and the pen
    point is pressed more into the tablet, thus more friction and -2- the
    springing back curve and friction curve are not linear.
    Do I need to consider more mechanisms to shed more light on the issue?

    I will, of course, post a summary of responses.


    Gijs Bloemsaat

    __________________________________________________ _________
    Gijs Bloemsaat
    Nijmegen Institute for Cognition and Information
    University of Nijmegen - Dept. of Experimental Psychology
    Room B.01.02
    P.O. Box 9104, 6500 HE Nijmegen, The Netherlands
    Voice +31 (0)24 3612758 Fax +31 (0)24 3616066
    __________________________________________________ __________

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