I hate this scale, it says low battery and shuts off after just 3 months of sitting in the drawer. It infuriates me that there’s still a lot of energy in the battery, I can use that in remote controls with no issues
If there’s enough battery to say “low battery”, then there’s enough battery to show the measurements!
It’s actually a plastic ribbon with a metallic foil in a zigzag pattern on top of it. It’s extremely cheap and does a pretty good job. It usually sits on top of a metal bar that can deflect a tiny little bit.
You can read all about it here: https://en.wikipedia.org/wiki/Strain_gauge
The main effect is that the resistance depends on the geometry. So as that changes, the resistance changes as well.