Whoah there: Your typical (cheap) consumer scale will have four (50kg) load cells hooked up to an hx711 (or clone) and the cheapest microcontroller the manufacturer could find that can drive an LCD directly.
Even the cheapest load cell is pretty damned accurate and the average between the four of them is going to be accurate within 0.1kg (~0.22lbs). Having said that, load cells have this problem where their values drift over time but only if there's a constant weight on them. If you step off the scale and allow it to re-calibrate itself (which is what it does every time it turns on) there will definitely not be enough drift to matter from a, "how much do I weigh?" standpoint. All it takes is like 2 seconds without weight for a load cell to "settle down" back to its not-actually-very-noisy resting position.
I've tested loads of the cheapest possible load cells money could buy along with some load cells I took from an expensive transparent scale that had cracked. They were all far more accurate than I was expecting and any differences between them was negligible.
The longer you wait before weighing something the less accurate it'll be but only by tiny, negligible amounts. Like, if you're weighing something that's 100kg and you waited ten minutes after calibration (something most scales won't allow because they all have something like a 30-second timeout) you'd still get a value that's within 0.01 of 100kg. They don't drift that much at rest unless there's some serious temperature variations or you had something resting on the scale the entire time.
When you cheap out on flextures, it's not the accuracy under ideal perpendicular loads that goes, and cheap housings struggle to provide ideal perpendicular loads. These are not particularly difficult things to get right, but the construction of even relatively expensive ($150) scales is so cheap that it screws this up and results in >1% deviation over the surface of the scale if you bypass the digital cheating mechanism.
Is it a big problem? No, but there's a fake decimal and an attempt to hide that the decimal is fake. Not cool.
What the heck are you talking about? The only flexure to speak of is within the load cell itself and... Can you even call that a flexure? It's a teeny tiny strain gauge mounted on a piece of steel that's going to bend ever so slightly when a weight is put on it. Even the cheapest load cells are precision-manufactured well within the tolerances necessary for the strain gauge to give you damned accurate results.
I've never seen a human weight scale that went beyond a single decimal place and in all honestly they're going to be very accurate. If you get on the scale and it says 201.2lbs that measurement is going to be accurate within ±0.1lbs (actually, more than that but you only get one decimal point of precision). If you put the scale next to something that's emitting a ton of electrical noise then maybe it'll be off by 0.2lbs but I doubt it.
Meanwhile, a precision of +-0.1lbs to measure humans is entirely superfluous. You can fluctuate an entire pound over the course of a day and your weight is not normally stable day to day. Analog scales only gave you about 2 sig figs, and that was probably a better outcome.
Thanks for posting, this explains why a $20 scale I got off Amazon which for some reason doesn't have the memory/smoothing feature is so impressively linear.
My cat sat on it, read 9.4lb. I stood on it, it gave my weight, then I picked up my cat and it read (my weight + 9.4)lb.
Even the cheapest load cell is pretty damned accurate and the average between the four of them is going to be accurate within 0.1kg (~0.22lbs). Having said that, load cells have this problem where their values drift over time but only if there's a constant weight on them. If you step off the scale and allow it to re-calibrate itself (which is what it does every time it turns on) there will definitely not be enough drift to matter from a, "how much do I weigh?" standpoint. All it takes is like 2 seconds without weight for a load cell to "settle down" back to its not-actually-very-noisy resting position.
I've tested loads of the cheapest possible load cells money could buy along with some load cells I took from an expensive transparent scale that had cracked. They were all far more accurate than I was expecting and any differences between them was negligible.
The longer you wait before weighing something the less accurate it'll be but only by tiny, negligible amounts. Like, if you're weighing something that's 100kg and you waited ten minutes after calibration (something most scales won't allow because they all have something like a 30-second timeout) you'd still get a value that's within 0.01 of 100kg. They don't drift that much at rest unless there's some serious temperature variations or you had something resting on the scale the entire time.