Why do digital scales measure this way?

[thrasherpix]

I've lost the only person who could answer this for me.

I think my scales are fairly accurate. Though they can shift up to 10 pounds in a day (usually not that much), it makes sense, and if I weigh myself again a couple of minutes later (careful to stand the same way) it will stay the same, so I don't think it's broken.

The mechanical scales that weighed me at a clinic had me weigh less than my digital scales do, as in that was the lowest weight. I'd rather have mechanical scales, but I couldn't help but wonder if theirs needed to be recalibrated. But maybe it's the most accurate. I wish there were more mechanical scales around where I live for me to test myself on.

But something weird came up that really has me confused, and what I'm asking about. I carried home a heavy pack of groceries that were an extreme relief to get off my back, and curious, I put them on the scales for it to say about a hundred pounds (45 kg).

Impossible.

So I tried a vacuum cleaner and it said like 170 pounds (77 kg), and again, impossible. So I got onto the scales while holding the same vacuum and it only added about 25 pounds (11 kg) to my weight, which strikes me as accurate (a bit on the heavy side even then, but in the believable range).

Anyone understand what's going on here?

 

[thrasherpix]

I'll only ask one more time in few words in case it helps. If no one answers after this then I'll have to assume no one here has any idea.

Why do my digital scales say my vacuum cleaner weighs 170 pounds/77 kg if I place it on the scales, but if I hold it myself while standing then it's only 25 pounds/11 kg?

 

[famicommander]

Is it on a completely level surface/is it assembled so that the part you step on is level relative to the base? If it's not, putting pressure on different parts of the scale will yield different weights even with the same mass object. Also make sure it has fresh batteries if it's not one you plug into the wall. Also check the settings to see if there's a zero/neutral setting; if so, make sure the scale is on a completely flat surface and settled, then zero it.

If that doesn't fix it, it's likely just worn out. Unlike with a mechanical scale there's not much you can do to troubleshoot or repair them.

 

[DeepBlueJoy]

Carpet. Scales dont work well on carpet