From: jthorn@astro.indiana-zebra.edu   
      
   Phillip Helbig (undress to reply) wrote   
   > >> In fact, the difference between your real weight (i.e. that   
   > measured at rest with respect to the Earth) and what you measure   
   > in the elevator is an indication of the acceleration.   
      
   Luigi Fortunati  wrote:   
   > I was careful to weigh *after* the initial acceleration and *before* of   
   > the final deceleration, both uphill and downhill.   
      
   How do you know that the vertical acceleration was zero during your   
   measurement intervals?  Do you have data from an accelerometer and/or   
   an independent measure of the elevator's position as a function of time   
   (see below)?   
      
      
   Luigi Fortunati  also   
   > Furthermore, my electronic scale is very tested.   
      
   Since you've tested it, can you tell us its integration time and/or   
   sampling frequency (i.e., the number of *independent* results per   
   second it produces), and how these compare with the relevant timescales   
   of the elevator motion?   
      
   Also, note that some scales act as "rectifiers", spuriously introducing   
   a DC bias into their results when high-frequency vibrations (as might   
   be produced by an elevator's guide wheels rolling on their tracks) are   
   present.  Is your scale tested for this?  If so, what's its rated   
   vibration-as-a-function-of-frequency-envelope for achieving accurate   
   results?   
      
      
   > Since the experiment is reproducible easily, I invite everyone to repeat   
   > it personally in their lifts and to report their results here.   
      
   To usefully study what's going on here, we need *both* the scale-measured   
   apparent weight as a function of time, and an independently-measured   
   position as a function of time.  The latter could be obtained by, e.g.,   
   using an open-cage elevator and sighting to a stationary scale fixed   
   to one of the elevator-shaft walls.   
      
   With this data, we could compare the apparent weight to the second   
   time derivative of the position.   
      
   Without all of this data, we don't actually know that the elevator was   
   indeed moving at constant vertical velocity during the measurement   
   intervals.   
      
   --   
   -- "Jonathan Thornburg [remove -animal to reply]"    
      Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA   
      currently on the west coast of Canada   
      "There was of course no way of knowing whether you were being watched   
       at any given moment.  How often, or on what system, the Thought Police   
       plugged in on any individual wire was guesswork.  It was even conceivable   
       that they watched everybody all the time."  -- George Orwell, "1984"   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)