Z axis calibration idea

[mike_biddell]

Having a think about this............. how about a finely graduated scale on the side of the tank (printed and laminated) and an optical mouse chip on a float. The chip returns changes in Y as it floats up the scale. This is a robust solution, which could have amazing accuracy. Plus, dirt cheap.

They have a resolution from 300 dpi up to at least 800 dpi. So about 3 thou up to just over 1 thou.......... that shud be plenty.