# How to measure water height thickness on infinitely flat surface with constant layer of water?

How would it be possible to measure layer of water on an infinitely flat surface, with every time different, but constant layer of water?

I'm trying to measure thickness from $$1\rm\,\mu m$$ to $$5\rm\, mm$$. I've already tried conductivity, but I'm only able to measure precisely from $$0.5\rm\, mm$$.

I need to find a way to get more precise result than that; maybe ultrasound, resistance, etc.

Any idea?

• I'm pretty sure you don't have an infinite surface! So, something simpler, can you weigh your experiment and get at how much water there is that way? Apr 6 at 14:17
• Are you assuming a uniform gravitational field? Apr 6 at 14:53
• For thicknesses below 5mm I would use an optical method such as interferometry. Apr 6 at 19:16
• @JohnRennie in theory, because it's road and the measure point will be somewhere in the middle, and height is my point, need to determine rain at any time on the pavement. Apr 7 at 16:10