Capacitive sensor to water surface for slideway measurement

[Earl Sigurd]

Has anyone built one of these or used one? In Connelly's Machine Tool Rebuilding he refers to the use of one.

I can find no reference online to a sensor of this type (Apart from bulk liquid level in tanks)

A quick calc says a 2" square about 40 thou from a conducting surface will have a circa 10pF value. Could be wrong!

[old mart]

It would probably not be practical as temperature and relative humidity variations would affect repeatability.
Keeping the water at a constant level would be difficult.

[TGTool]

Since water finds its own level relative to the earth, it's a perfectly good way to level up a long machine or other equipment. Yeah, the water may evaporate over time, but you're only talking the time it takes to do a measurement from say a machine table to the water surface on each end and it won't change enough to measure. I'd always thought you could just do a depth mic down to the water surface, and if you were slow and attentive you ought to be able to get a repeatable measurement within a couple thousandths. Electronic proximity might be able to do better but I can't make any contribution there.

[J Tiers]

Used to be done all the time with a "hook gage" to find the water surface, I believe.