PeterH:
Didn't realise it was a poll. It's a perfectly feasible solution, and the only thing I don't much like about it is that it seems to require moving parts which I think would be problematic in a hygienic environment. And just about all the other solutions being suggested suffer from a similar problem.
Peter,
Not a moving part. You lower a weight into the liquid and tie the string to a force gauge. The weight balances with gravity, buoyancy force and string. If specific gravity increases then buoyancy force increases and string force decreases. The force gauge reads it as a decrease. The weight stays immobile, no moving parts. We do this lab in intro physics labs to determine salt water density with a 0.1g accuracy balance. The result is not bad. With a floating meter you can read it but salt starts gathering on it and the reading is affected. I imagine similar effects with floaters inside the liquid.
Well, this other guy is doing a vote all by himself, apparently that is what he considers as a vote. I must have not learned my English well enough. Sounds like communist vote. One person votes 