I'm another one of those guys who wants to use Arduino to automate and monitor homebrewing. It's nothing too complicated, just manage a heater pad using a thermometer mostly, but I'd also like to monitor the specific gravity so I can check it out without opening it up. There's been a few threads on this but I haven't seen a single on where they came up with a good answer, mostly due to all the different types of gunk you'd get in a fermenting bin while it's doing it's business.
I figure the best way of doing it is to recreate the normal method of measuring the pressure with a flotation device. My plan is just to create a buoy with a pressure sensor on the bottom (eg. http://uk.rs-online.com/web/p/pressure-sensors/2355762/).
There's a couple of issues here, the weight of the wire on the buoy is going to affect how deep it floats, it won't be super accurate but I'll just have to regulate it as much as I can.
Bubbles may form under the buoy, I'm going to have to shape it so that bubbles don't get to bad, as long as they're relatively uniformed across the batches it should be fine. If I make the buoy big enough and put enough weight on it I'm hoping they won't throw it off too much.
I'll then have a wire hanging off the bottom of the buoy to drop the sensor down a bit and then attach a weight to the end of it. I'll calibrate it afterwards and I'm hoping this will give me semi-accurate readings? They don't need to be outstanding, just good enough to work with.
Can anyone spot an obvious flaw that I'm missing here? Will the pressure sensor be accurate enough?