eli5 how does a electronic weighing scale work ?
In: Technology
There are materials that change their electrical resistance if they get stretched or compressed. If you attach strips of them to a metal bar, you’ll be able to measure how much said metal bar bends. If you fix one end to a frame and put a plate for people to step on at the other end, people will slightly bend the metal bar.
There’s a little doohicky called a [strain gauge](https://en.wikipedia.org/wiki/Strain_gauge). It’s basically a bit of resistive material painted onto a thin piece of plastic, sort of like a printed circuit board. When it gets stretched or squashed, its resistance changes. It’s about the size of a fingernail.
You glue it onto the side of a block of something, then when you put a weight on the block, the block gets squished slightly, and the strain gauge can be used to measure the amount of squishing.
For example, even insanely heavy things can be weighed using strain gauges. Make a big steel block large enough to hold the thing you want to weigh. Glue some strain gauges around the block. Roll the heavy thing onto the block and measure the change in resistance on the strain gauges.
Fun fact: ordinary resistors (at least the carbon kind) will behave the same way, but they’re not so easy to glue onto the sides of things, and probably not nearly as precise.
Source: had a summer job working with the things when I was a kid. I soldered the leads onto them (tricky!) and then glued them onto the thing to be measured.
Latest Answers