Hi, I am looking into making what will essentially be 3 sets of scales (each one being made of 3 force sensors sandwiched between 2 polycarb discs). These will be used to estimate the amount of beer left in some homebrew kegs so I know when to start brewing again and avoid running out of beer (don't want to move the kegs as this could disturb any sediment that might collect in the bottom of the kegs). I have been looking at some piezo force sensors and force sensitive resistors. The FSRs on Sparkfun are not recommended to be used as scales so that leaves the piezos, and at $20 a pop (from Sparkfun also) that blows my budget by miles. Does anyone know what electric scales use, as I have seen these for about $20, so (assuming they have 1 sensor per foot otherwise they would be hugely inaccurate depending where you stood) this would be $5 per sensor (max).
So, what do you guys recommend using? Could I just grab a few electric scales and use the sensors out of them? or should I go with the Sparkfun sensors (even though they seem a bit expensive), I can't find anything on eBay, etc but I'm probably not searching for the right word! A bit more info on accuracy, the kegs hold about 20 litres each so I'm assuming that's 20 kgs, and I will probably display an output in 5% steps (so 1 kg steps). The empty kegs are about 3.5 kg. So I would want to measure between 3 - 24 kgs in increments of 1 kg +/- 0.5 kgs. Any help or insight is much appreciated. Cheers!