bathroom scale hysteresis

john.ruckstuhl · 2005-05-28T00:35:03+00:00

Sneaky scales fudge weights deliberately.I suspect that many modern, microprocessor -controlled bathroom scaleshave programmed in hysteresis to increase user confidence in thescale's accuracy. The scale remembers fresh measurements, say 166.2#,and if it next measures same weight +/- a little (within a short time),say 166.8#, then the scale decides to report the *original* measurement166.2#. Neat. Sneaky. User believes the scale is highly repeatable.On such a scale, I weigh myself multiple times and get the same reading(to the 0.2#) each time. 166.2#, 166.2#, 166.2#, 166.2#, ...Then I weigh something different (myself holding a load), to reset thememory.Then I weigh myself again... Now, get something like 166.8#, 166.8#,166.8#, 166.8#, ... very solid again, but 0.6# different from 1stseries of measurements.I tried 6 models (2 or 3 brands) at a retail store display and findthis "feature" common.Is it important? Maybe yes in the following scenario -- in some sportslike wrestling, boxing, judo, you have multiple competitors weighing inat the same time, same scale, with possibly very similar weight. Somecompetitors are concerned with as little as 0.25#. In this case itseems one competitor could inherit the weight measurement of the personin front of him.In a perfect world, competition weigh-in equipment should becertified/calibrated. But since the bathroom scale appears sorepeatable, some competitions now use modern, microprocessor-controlled bathroom scales.Somebody's going to say... "you shouldn't do that". Right, I agree.But (a) it's happening, because (b) this hysteresis (memory)phenomenonisn't widely known, I suspect.Anyone care to confirm? Contradict? Repeat the experiment on theirown scale? Comment? In my experiment I didn't bother to determinewhat weight difference resets the memory -- 1#? 1.5#?Regards,John Ruckstuhl

May 28, 2005 40 Replies

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Seth Breidbart 21 years ago

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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