[HN Gopher] Passive damping - Bathroom scales
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Passive damping - Bathroom scales
Author : surprisetalk
Score : 57 points
Date : 2024-09-09 15:58 UTC (3 days ago)
(HTM) web link (thinking-about-science.com)
(TXT) w3m dump (thinking-about-science.com)
| Syzygies wrote:
| Most consumer bathroom scales are programmed to report exactly
| the same reading twice in a row, when the reading is close.
|
| Passive damping may be smart, but stupid always wins.
| bobbylarrybobby wrote:
| Interesting. Mine consistently shaves off ~2 pounds if I weigh
| myself twice in quick succession.
| lultimouomo wrote:
| This happens on mine if I don't let the scale calibrate
| before the first measure. The scale turns on if you step on
| it, so it's tempting to just put both feet on in quick
| succession while the scale it's still off. That will give you
| a wrong reading. If you step off, the scale calibrates, and
| the next reading will be right.
|
| You should get two equal readings if for the first one you
| push on the scale with one feet, take it off, wait a few
| seconds, then weigh yourself.
| UniverseHacker wrote:
| Oh wow I always wondered why this happened as it felt vaguely
| weird, I was skeptical that these things were accurate enough
| to be so repeatable, but never suspected this.
| gurjeet wrote:
| This is why, between two successive measurements, I place one
| foot on the scale to measure the weight of just one leg (comes
| to 18-20 lbs). And the following (third) measurement is
| sufficiently different from the first one. I use this "weird
| trick" when I'm not happy with the first reading, and want a
| second opinion ;-)
| 01HNNWZ0MV43FF wrote:
| That explains why I've sometimes weighed myself, peed, and then
| found that I gained weight
| gruez wrote:
| I bought a cheap $20 off amazon and it was seemingly accurate
| to 0.1 lb. I tested by weighing myself plus a bowl with varying
| amounts of water and there's no "report the same weight if the
| measurements are close" behavior you describe.
| rainbowzootsuit wrote:
| Often I see these mixed up:
|
| Damping is restraining oscillation.
|
| Dampening is making something wet.
| groestl wrote:
| In German, "dampfen" means all of the above, and also "cooking
| in hot steam" :)
| lupire wrote:
| Dampening is also restraining.
| amluto wrote:
| I've never taken apart a bathroom scale or tried to measure any
| of the above, but my intuition is that this article completely
| misses the point. Bathroom scales don't deform a whole lot, and
| humans are squishy! When you take a running leap onto a
| playground swing, you are part of an oscillating pendulum. When
| you step onto a scale, sure, there will be a transient, but there
| will also be a whole lot of noise as you balance, wiggle,
| breathe, etc, and I bet the latter is dominates the former.
|
| A self-respecting bathroom scale (not the kind that is
| intentionally biased to read the same number twice in a row) acts
| like a moderately low-pass-filtered sensor. As you move a bit,
| _the number changes_.
|
| So the scale is averaging over time, not waiting for some very
| stiff internal spring to stop oscillating.
| NotYourLawyer wrote:
| That does seem likely. You gotta think the scale is stiff
| enough that it'll settle down in well under a second.
| senectus1 wrote:
| when I renovate my bathroom I'm making a perfectly flat surface
| just for the scales. Bathroom floors are not flat and when you
| put scales on them the torquing of the scales messes with its
| mesurements.
|
| I can move my "smart scales" around the room and get a different
| result each time.
| Yodel0914 wrote:
| It would be less work to turn "bathroom scales" into "bedroom
| scales". Bathroom floors are not level for a good reason.
| quesera wrote:
| > _Bathroom floors are not level for a good reason_
|
| Most residential bathrooms do not include a drain in the
| middle, at least in my part of the world.
|
| Most residential bathroom floors here are as level as the
| tradesman can get them.
| 1d22a wrote:
| Huh, interesting. That's not the case in Australia, in all
| the houses I've seen. I always thought it was smart,
| though.
| quesera wrote:
| It's very common (maybe even code?) in commercial
| bathrooms in the US as well.
|
| Not sure if the residential code is lagging, or if it's
| just not a popular design here.
| Loughla wrote:
| Is it really that important to weigh yourself THAT accurately?
| Your weight fluctuates throughout the day anyways, right?
| Terr_ wrote:
| Yeah, even with a perfect measuring-scale, people should be
| ignoring its daily reading in favor of a running average
| across multiple days.
| adrian_b wrote:
| A running average is useless for something like a weight-
| losing diet (or for a weight-increasing diet). It is good
| only for verifying that your weight is stable.
|
| When you are serious about losing weight, you must measure
| your weight every day at the same time and in the same
| relationship vs. eating/drinking and eliminating that.
|
| You must lose weight neither too slow, nor too fast. A rate
| of around 100 to 150 grams per day is good.
|
| Especially at the beginning of losing weight, accurate
| measurements of the weight are essential for adjusting the
| diet, i.e. when there is no weight loss one must eat less,
| and when the weight loss is too great, one can eat more.
|
| A running average could not guide efficiently your
| decisions for the current day, whether to eat more or less.
| Most likely it would result in big oscillations around the
| ideal weight losing rate.
| gruez wrote:
| Can you really measure your weight that accurately? What
| about your body's hydration level, or whether you've just
| taken a dump or not? Those would probably skew your
| measurement by half a pound.
| adrian_b wrote:
| Like I have said, you have to take the measurement every
| day at the same time and in the same order with respect
| to eating, drinking and dumps.
|
| And yes, you can measure that accurately.
|
| I had been obese for many years and I had many failed
| attempts to lose weight. This has changed only after I
| bought accurate digital scales and I have started to
| measure carefully, every day at the same time and in the
| same conditions.
|
| During a day, your weight will vary a lot, perhaps by
| more than two pounds between the maximum and the minimum.
| Nevertheless, if you take care to measure at the same
| point every day, the accuracy is good enough, the
| uncertainty is less than 1/10 of a pound, if you are
| careful.
|
| When I was losing weight, I could see very clearly the
| effect of eating one spoon more or one spoon less per day
| of certain foods, so I was eventually able to lose one
| third of my initial body weight, in about ten months.
| Terr_ wrote:
| > A running average is useless for something like a
| weight-losing diet
|
| I disagree, it worked fine for me, validating my ongoing
| calorie limits and estimates across several months and
| dozens of pounds.
|
| > A running average could not guide efficiently your
| decisions for the current day, whether to eat more or
| less.
|
| That's just using the wrong tool for the wrong job. You
| don't don't starve yourself today because you were
| constipated yesterday. (Or if you do, it's for issues of
| immediate discomfort rather than a dieting goal.)
|
| Instead, you eat a consistent number of estimated
| calories, adjusting it to fit the observed trend in
| weight loss.
|
| Paying too much attention to daily data points is also a
| psychological danger, people will put too much emphasis
| on noisy/singular data point and then use that as a
| rationale to give up or cheat.
| cruffle_duffle wrote:
| Just build it into the floor like they build truck scales into
| the road.
| seanhunter wrote:
| ...or just gain weight up to the point you can use an actual
| truck scale to weigh yourself. Seems more efficient to me.
| dspillett wrote:
| That leaves you with a problem when it breaks, or the maker
| goes out of business so all the smart features (or in some
| cases the basic ones too) stop working, or the maker decides
| it isn't taking enough money from you so starts hawking ads
| before it'll show you any or your information, ... You'll
| probably have a remodelling job to do to make any replacement
| device fit, rather than just placing the new device on the
| same flat surface.
| alliao wrote:
| thanks... I can rest easy that this is possible cause to why my
| kitchen scale is so slow... do not get a SOEHNLE Page scale if
| you value your sanity. It is so slow it can serve up counting
| down ads....
| euroderf wrote:
| I tried repeatability on a few electronic scales at the shop and
| none had it, so I stuck with my old mechanical scale. Reason: It
| Just Works.
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