This is stretching things a bit, but I’ve found a weirdness in one electronic bathroom scale that could foul you up here.
The bathroom scale I studied appeared to be programmed to keep repeating the same number as long as the weight on it was pretty close to that number. That is, if you weigh yourself, and then weigh yourself again, all digits always repeat. This is a precision of 0.1% for that scale. Now, if you weigh yourself, and then weigh yourself holding a several pound weight, and then weigh just yourself again, your two no-extra-weight values will vary by several tenths of a pound. This appears to be the actual precision.
I think they built in this repeating trick to reduce consumer complaints. Which, of course, convinced this particular consumer that they taught his scale to lie.
But with vehicles, slight inaccuracy of height are taken up by the tires and suspension…
With the table, you can’t that with all four legs…unless you put foam under each leg so that the weight on each leg is fairly constant despite the change in height of legs…
So what you can do is put the scale under a spreader (eg a 4x2 between the legs.) that carries two legs at that end… and put the scale centrally under the spreader …
next, since you know the table is symmetrical, you can just weigh one end and double it.
The OP is suggesting four scales, though. Maybe one of the legs is short and so two of the scales take essentially all of the load. That’s ok, though, since you’re just adding everything together. 0+50+0+50 is the same as 25+25+25+25.
The table is probably symmetrical, but weighing each leg eliminates that problem totally.
Weighing just one side also introduces some inaccuracies that wouldn’t be present when weighing the corners.
An easy way to test this is to get two scales and weigh yourself with one foot on each scale. Add them together and see if the total matches the weight while standing on just one scale.
The gotcha is the weighed object has to stay level, or be in the same orientation as you weigh each “leg”. The weight at each position is the weight depending on the location of center of mass - if that position is different between measurements, i.e. tilt this way then that way, the result will be inaccurate. You put more weight on your wrists on all fours than leaning on the counter, for example.
Spring scales are notoriously unreliable. I can shave a few pounds off my weight by standing off center on my scale - until I can’t stay balanced on the back edge of the scale.
Yes, this. They’re programmed to display a consistent weight until the change is a couple of pounds, then they jump to the new weight.
At one time I weighed myself every morning without fail. Always in the exact same test condition: fresh out of bed, freshly peed, and naked. The scale displayed weight in pounds to 1/10th of a pound. e.g. 151.2 lbs.
My weight would not vary at all, not even by the minimum resolution of 1/10th of a pound for a week or more, despite wildly varying eating the prior day. Then one day my weight would jump about 1- to 1-1/2lbs to a new value. Then remain steady for a week at the new value before jumping again, either up or down.
Very clearly the scale was recalling prior measurements and repeating them verbatim until the new data differed from the old by some specific delta. Which delta was 10-20x larger than the resolution of the scale. Bastards.
And no, there was no mention of this behavior on the instruction sheet.
Ref somebody else upthread, restarting the scale had no effect on its memory of prior values. I took to out-smarting it by weighing myself each time with and without a 5lb weight in hand. That was a big enough delta that it invalidated the history and suddenly my displayed weight was fluctuating by a few ounces to a lb. or so every day. As it really does for all of us.
Does being level really matter? If one end of the table happened to weigh a little more than the other end, wouldn’t the two scales on the heavier end show slightly more weight, and the two scales on the lighter end show slightly less weight, thereby offsetting one another?
With 4 scales at once, it doesn’t matter - only the calibration/accuracy of the scales matters.
If you are economizing and using one scale, or using one scale for consistency, then the table must be at the same angle as you measure each leg. Tilting the table changes its center of gravity and hence the weight distribution on each leg. Hence the race car example above where there are 3 blocks to keep the car level as you measure each point.
Of course, unless it’s a weird table or is loaded up, symmetry should apply - there’s no physical difference between corners, so the weight should (should) be the same on each leg on a level table. I presume the purpose of measuring all 4 legs is to prove this.
THANK YOU! Some people told me I was nuts and most didn’t seem to understand what I said it was doing, when I shared this discovery. And what you describe works; I’d grab a heavy container or book to use between meaningful weighings.
I wondered how they meant to deal with households where more than one person weighs themselves every day. Unless their weights were close to identical, this cheating scheme to appear more precise than the scale actually is wouldn’t work.
The scale I had was able to be set up with up to 4 users. It also had skin resistance measuring features to do BMI/body fat estimates. Which features we did not use. But if we had, we’d have had to push “our” button before weighing ourselves so the right history would be updated.
But …
My wife weighed about 20# different from my weight. Using none of the personalization features, the scale seemed to be smart enough to remember my weight and separately remember her weight. So from day-to-day I’d show the same 140-something value to the tenth of a pound and she’d show the same 120-something value to the tenth of a pound. Presumably they had some other delta programmed in that meant “this is somebody else.”
The “weigh yourself with and without holding a couple pounds of ballast” trick served to fool the scale separately for both of us so we both got different daily true weights.
Your scale may vary of course, but this demonstrates what at least one cheapo Chinese scale from Target was able to do.
This one says it has four sensors. You can see in the photos that it has conduit connecting the four feet that is separate from the glass panel, but they’re not structural elements. Our scale has just thin insulated electrical wiring that’s taped or glued to the underside of the glass to connect the four feet to the display unit; the only structural element connecting the four feet is the glass pane itself, so there’s no way for load to be transferred from one foot to another.
Which is confusing, because depending on what you’ve had to eat or drink and whether it’s still in there, your weight can fluctuate a pound or two. One cup of water is 8oz or half a pound. A scale that’s consistently exact to the tenth of a pound is obviously not correct.
I assume you mean that it tells you the exact same weight if you try again within a minute or two (I.e. approximately the same weight is placed on the scale a minute or a few minutes later.)
It’ll tell me I weigh 142.3 lbs today, tomorrow, and the next day. Then it’ll jump to e.g. 144.5 or 140.6 and show that exact same weight for several more days.
It only changes my displayed weight if it’s more than about 1.2kg different from last time. Being a Chinese product I’ll bet a chunk o cash it’s programmed in SI units even though it has a switch to set the display to pounds & tenths of pounds.
True enough. I don’t know about LSLGuy, but in my case, this surprising behavior is what triggered my experiments trying to figure out what the heck it was actually doing.
And I’d bet otherwise. I bet it’s programmed with integer math based on the A/D converter output. It may only display in English units, or it may also display in SI, and there may be a switch or some other form of input (maybe a magic mushroom of some kind), but the units conversion happens very late in the process, well after the trickery with remembering multiple users’ last weights.
I was going to say I’ve never experienced the same with my scale, but I did some experiments and it works the same way. However, mine has a threshold of roughly a pound. My weight varies about that much daily (despite also weighing myself just after using the toilet and before stepping into the shower, at the same time every morning), so for the most part I don’t experience it. But I tried some experiments with small weights, and I can definitely see that small changes are not displayed. It may have been a 500 gram threshold, though it seemed to be reliably under a pound. It may simply be 1024 ticks on their analog-digital converter or the like, with a tick corresponding to whatever arbitrary conversion their load cells produced.
I had a co-worker who thought his weight was holding steady at 210 pounds until he went to a medical appointment and they measured his weight at something like 20-30 pounds more. He didn’t realize that his bathroom scale topped out at 210 pounds.