Lets say I have a large, heavy, table that I want to weigh. I have no means to get the entire table onto a single scale.
If I were to take 4 bathroom type scales and put one under each leg of the table, then add the total weight indicated on the 4 scales, would that be an accurate weight of the table? What am I missing? Thanks for any input.
Accurate? Probably not, but a near estimate if the scales are on a hard surface, reasonably accurate and the whole thing is level.
You can improve accuracy by testing each scale with a known weight somewhere near the weight one leg will impose. If they all agree, that would be a good start. If you only had two scales and supported the other two legs so the table was level, you would probably be able to get an equally good result.
Bathroom scales are notoriously inexact. An alternative would be to measure 4 times while rotating the scales from leg to leg. Each scale should measure the same (assuming they are equal thickness) but if one consistently measures different, it may need calibrating.
I wonder if - you do your measurements, but switch scales so each has a turn at the same leg. Ensure that you calibrate them all to get the same reading at that leg. DO they now consistently read the same under each other leg? However, without calibration, all you have is a way to compare this weight to other tables.
As I understand, this concept is not far off. I have heard of truck scales where they will measure the front axles of the truck, then the back axles, to get the total weight (close enough) since the truck is pretty much level during the process.
This would work to the extent that the bathroom scales were accurate.
Presumably if you’re trying to get the weight of a large table, +/- 5-10% is probably close enough. It’s not like a moving company charges by the microgram.
There are also weight limits per axle.
Don’t give them ideas.
This doesn’t make sense to me because the weight is being distributed over distance.
Like, the basic physics of it?
All of the table’s weight has to push against the stuff it’s resting on somewhere. If it’s all resting on springs, then you can measure how much those springs deflect. That’s what the scales do.
Like, if you had a really big scale with multiple springs in it and the table could sit on it, then you’d have the same system. Measure how much all the springs deflect. There’s no reason for the plastic body of the scale to be that big though, because all that matters is the springs.
I’ve been Googling, and the two sources I could find that address the issue say you have to add up the weights of the separate scales. In other words, if I weigh a 200 pound table on 4 scales, each scale would roughly register 50 pounds. That makes sense. How could each separate scale show 200 pounds?! Makes no sense.
You have it right. If you had 4 people standing on scales individually, you’d add their 4 weights to get their total weight, even if they held hands, even if they were standing on a solid platform that spanned all 4 scales.
Yes, you add the weights. Is anyone suggesting otherwise?
I guess i misunderstood one of the statements I read. Thank you for the clarification.
We did this with race cars. They sell a small scale to place under a wheel and the kit comes with 3 blocks that are the same height as the scale… You place the scale under one wheel at a time. The total of the 4 readings is the car’s weight and you also get the front/rear and side to side bias.
If you’re using NON-electronic scales, then all the above is reasonable. But the electronic bathroom scales which I’ve used have a major problem with the idea posed by the OP.
Here’s how to use an electronic scale in my experience:
- Tap the scale to reboot the computer.
- Get onto the scale and wait a few seconds while it contemplates the situation.
- Read the readout to see how much you weigh.
After step 3, it is futile to get another reading by holding a new item, or getting rid of an item, or moving a leg to a second scale. For example, you can’t weigh yourself, and then pick up a packed suitcase to see what the total is of your weight and the suitcase’s weight together. You’re going to have to start all over with step 1, with both you and the suitcase on the scale.
Similarly, once the scale is properly under one leg of the table, it does its thing, and I’m not clear on how you plan to reset the 4 scales when they’re all in the final position.
I don’t know what type of scale you are using, but I know from experience that many bathroom scales give erroneous readings if the weight is concentrated in a small area (i.e., on a small table leg). They seem to be more accurate if the weight is spread out similar to two feet on the surface. Maybe use a book or something to spread the weight out?
I tried to weigh a metal bar I was shipping and it weighed differently when I held it in different places on the scale. I finally ended up just holding it in my hands and then subtracting my own weight. Who knows if that was accurate…
YMMV
Lift up the table from all 4 scales, wait until they all reset, then put it back down. You’ll only need as many people as it takes to lift the table for 10 seconds.
My eletronic bathroom scale works in the reverse of what the OP is suggesting. That is, it has 4 legs with sensors on them which rest on the floor. I’m assuming the scale adds those 4 readings to get my total weight.
Why not use two scales, one at each end of the table. Have someone at each end lift their end as they step onto their scale. Subtract the two persons’ weights from the combined weight.
You could get a ball-park weight with one person and one scale doing it this way.
This is quite a surprise. I think the force gages are expensive, and scales use levers and beams inside to put all the force on one force gage. Separate sensors on each leg sounds much more costly.