On the subject of density measurement (a little OT, but it was raised), you have to be careful. Any attempt to measure density using pressure gauges requires that the "fluid" is homogenous, i.e. uniform in density throughout.
It is often a need to know the density of non-homogenous "fluids" such as Yeast Slurries etc., and in truth the only way to know the average density of the contents of the tank is to accurately know the volume (roll back a few posts), AND to know the overall weight (roll back a couple of posts)....
Faced with whatever it is you actually want to measure, and how accurate you want the results, you have a choice of several methods, and you choose whichever methods are applicable to your particular case, and of course how much money you have to spend on doing it.