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bathroom scale hysteresis

Discussion in 'Misc Electronics' started by [email protected], May 28, 2005.

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  1. James Meyer

    James Meyer Guest

    Occam might agree, but only if he never read the whole thread.

    Jim
     
  2. Ken Taylor

    Ken Taylor Guest

    Occam should have grown a beard - much simpler.

    Ken
     
  3. Andre

    Andre Guest

    Our bathroom scale has exactly the same problem - the same reading is
    repeated when you weigh yourself a number of times.

    If the first reading were, say 160.3, further readings would be either
    160.3 exactly, or something outside the range of 160.3 plus/minus 1.

    These results, I believe, is a result of clever firmware and not
    mechanical or sensor characteristics.
     
  4. GaryG

    GaryG Guest

    I have a hard time believing that they would do that. Why would they go to
    the trouble of "lying" to users of their product?

    If I noticed my scale doing that, I would not be happy. Fortunately, my
    4-year old Tanita does not seem affected by this problem (I've tested it a
    number of different ways, and never once noticed the problem described by
    the OP).

    Perhaps it's limited only to low-end scales.

    Oddly enough, nobody complaining about this "problem" has mentioned brand
    names either...
     
  5. Having spent some time in the weiging industry, i can assure you that
    the cheap portable bathroom scales that you buy are neither:
    a. repeatable
    b. accurate
    c. linear

    In fact, most will become more innacurate in the most common weight
    ranges.

    In AU, a cheap set is $20, a good repeatable set is $400. The
    expensive scale can be recalibrate and remains linear. Should it not
    be linear a multi-point cal can be done. The cheap set can only be
    thrown.

    Most cheap sets are innacurate of the shelf as they are made in china
    and fail to take into account local gravitational constants
     
  6. GaryG

    GaryG Guest

    Do you have any experience with the newer digital models? Not the low-end
    ones, but ones like the Tanita with ostensible 0.2 lb resolution, priced
    around $50-90 (US).

    For instance, http://tinyurl.com/49swe, or the more expensive German-made
    Soehnle brand http://tinyurl.com/3t6kt.

    GG
     
  7. Guest

    Hi,
    Thanks to all who took time to reply.

    Yesterday I went to a Bed, Bath, & Beyond store where there were
    several models on display.

    I brought with me several 0.5 liter water bottles (approx 1 lb.) and
    half-consumed one (approx 0.5 lb.) so that I could adjust my weight in
    0.5 lb. increments. I tried 3 models and found two that I think
    exhibited this programmed hysteresis, and one that did not.

    The $40 Thinner TH300 uses load cells and reports to 0.5 lb.
    Holding an empty shopping basket and full pockets, I measured at 181.0
    six times in a row. Then, holding ~0.5# in my basket, I still measured
    181.0. Again, holding ~1#, I still measured 181.0. Then, when holding
    ~1.5#, apparently past the programmed hysteresis threshold, scale
    reported 182.5.

    The $50 Tanita BF679 reports to 0.2 lb. It did not have hysteresis.
    Each measurement was independent, reporting like 178.2, 178.4, 178.6,
    178.4, ... (I wasn't holding an empty shopping basket for this one).

    The $60 WeightWatcher WW60 (Scales by Conair) uses load cells and
    reports to 0.1 lb.
    I (plus basket) measured 180.7 six times in a row. Then holding ~0.5
    lb., I measured 180.7 again. Then, holding ~1#, I measured 181.9 .

    So, I see this programmed hysteresis in some models, with a breakaway
    delta of ~1#.

    I had thought I originally noticed this two months ago in several
    Taylor models and a Tanita, but I wasn't able to test any Taylors
    yesterday and my one Tanita test didn't show it.

    Best regards,
    John Ruckstuhl
     
  8. GaryG

    GaryG Guest

    Outstanding report...thanks!

    My experience with Tanita has been the same - no hysteresis noted.

    Consumer Reports magazine tested several models of body fat scales in the
    last year or so. As I recall, they liked the Tanita the best - they warned
    that body fat was quite variable, and probably not very accurate, but that
    the body weight reported by Tanita was better than most other units (not
    sure if they tested for hysteresis).

    GG
     
  9. The high end Soehnle scales can be calibrated, but the ones show look
    like you standard cheap crap. I could well be wrong here. Some Soehnle
    stuff is quiet good.

    Tanita, never seen anything but cheap crap.

    The good scales I am familiar with are manufactured by a company
    called AND. Try do a google for AND though!!
     
  10. Guest

    I suspect that many modern, microprocessor -controlled bathroom scales>

    There's no such thing you jerkoff.
     
  11. I presume that he was referring to scales with an LED display. I imagine
    that these *do* have a microprocessor of sorts inside, to perform
    analogue-to-digital conversion on the output of a strain-gauge attached to
    the part you stand on, and then to convert this reading to signals which
    control the segments of the display.

    Now who's the jerkoff? ;-)
     
  12. Noah Little

    Noah Little Guest

    That's true. But the point in question was the "no such thing" put
    forth by a previous poster. That's clearly not true.
     
  13. Noah Little

    Noah Little Guest

    Occam like that, too.
     
  14. A balance scale at a gym I used to frequent had about a 5 lb
    difference at the 200 lbs mark, depending on whether you moved the big
    weight to the 200 lb notch, or moved it to the 150 lb notch and the
    small weight to the 50 lb mark.

    Seth
     
  15. I have a Taylor bathroom scale, with a 1# hysteresis. I weigh myself
    every morning. Each new weight is either the exact same as the
    previous weight or at least 1.2 lbs different. (The scale shows
    weight to 0.2 pounds.)

    Seth
     
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