Liquid level sensing device and methods of making an operating the same

Claim 1

A liquid level sensing device for determining the level of a liquid in a liquid confining means, said device comprising a pair of electrode plate means disposed in spaced apart relation so as to be adapted to be in a certain position relative to said confining means and having opposed ends, electrical means connected to said electrode plate means for creating a voltage signal means therefrom that varies in relation to the level of said liquid in said confining means relative to said electrode plate means, and means for determining the actual level of said liquid from said signal means, the improvement wherein a third electrode plate means is disposed in spaced apart relation to said pair of electrode plate means and is adapted to cooperate with one of said pair of electrode plate means to provide a reference voltage signal to determine the electrolytic base of said liquid, said third electrode plate means having opposed ends one of which is disposed adjacent one of said ends of said one of said pair of electrode plate means, said adjacent ends of said plate means being adapted to be disposed adjacent the bottom of said liquid confining means with the other ends thereof disposed adjacent the top of said liquid confining means, said adjacent ends of said electrode plate means respectively having portions thereof interleaved with each other in spaced apart relation while the remaining portions of said electrode plate means are not interleaved, the other electrode plate means of said pair of electrode plate means having one of said ends thereof disposed short of said interleaved portions so as to be adapted to be disposed above said interleaved portions when said interleaved portions are disposed above said bottom of said liquid confining means, the other of said ends of said third electrode plate means and said other ends of said pair of electrode plate means all being disposed adjacent each other.