specific gravity of paint

What do you call the device used to measure the specific gravity of paint?
I’ve a utility trailer that needs paint so I thought I would do it myself.
I now have a brand new air paint sprayer and need to know how to consistently adjust paint thickness.
I’ve spray painted before but the equipment was always set up beforehand.

You ned to measure viscosity, not specific gravity.

My HVLP sprayer came with a viscosity cup. Basically, nothing more than a calibrated funnel. You fill it up and time how long it takes to empty. If it takes longer than X seconds, then you have to thin the paint.

Yeah I knew it was some word I don’t use very often. Thanks
Thanks finaegel
Anyone know where you can buy a viscoyity cup???

These guys have one for $6.99.