yeah..we know that it has something to do with strain gauge..and usually for weighing its connect with a load cell....called strain gauge load cell..however this used for industrial machinery...and it is very expensive..so we want to find out what is in the electronic balance..so that it is much a cheaper alternative..n maybe we can use the same principle/circuit to help in our project..
so..i don't think strain gauge load cell is used inside..coz then an electronic balance would cost hundreds of dollars which is expensive for us..so what exactly is used in the electronic balance??
Buy a couple and take them apart, You can get the small pocket size for $10 or less, the bigger ones you can stand on and weigh yourself are $20 or so.
Its a strain gauge. Stick-on strain gauges can be had for a few dollars. You have to specify the metal you're sticking them onto, or different rates of expansion with temperature will make it a thermometer as well as a balance.
I've taken apart an old electronic bathroom scale and it looked like they have a movable core inside an inductor. There's a spring to counter the person's weight and as it's stretched it pulls out the core lowering the inductance. At least that's how I interpreted its design. I don't know if they all use strain gauges nowadays or not.