Quote Originally Posted by Slatye View Post
Build_platform.jpg

Something like this? So the green cylinder slowly displaces the water in the blue one, at a rate determined by how far open the valve is (and obviously the Peachy's water drop sensor gets attached to the valve).

There might be some issues getting the friction low enough on the O-rings; you might have to grease them before each job to keep them sliding nicely.
slatye.... your drawing is a million times better than mine....but the bottom cylinder must also be contained in the tank such that the when the saline is expelled it leaves the volume in the tank unchanged. If the weight is large, the O ring friction becomes a negligible factor. But thanks for grasping the concept so quickly as it is difficult to describe.