초록 ▼

A capacitive sensor is constructed to eliminate electrical conduction through a liquid being measured. The electrical conduction in the liquid occurs between the plates of the reference and measuring capacitors. The capacitive plates which are spaced from the common capacitive plate to form the refe

A capacitive sensor is constructed to eliminate electrical conduction through a liquid being measured. The electrical conduction in the liquid occurs between the plates of the reference and measuring capacitors. The capacitive plates which are spaced from the common capacitive plate to form the reference and measuring capacitors are of unitary construction and formed from anodized aluminum. The anodization forms an insulated surface which prevents conduction between the electrodes through the liquid. A ratio taken between the measuring capacitor and reference capacitor is therefore indicative of the level of the liquid within the gap of the measuring capacitor and is independent of the conductance of the liquid and its dielectric constant. Such a probe is particularly useful in applications where the liquid undergoes indeterminable changes in conductivity such as a lubricant which becomes contaminated by metallic particulates.

대표청구항 ▼

A capacitive sensor insertable into a reservoir containing a liquid wherein said liquid undergoes indeterminable variation in contamination and electrical conductivity, said sensor comprising: a first electrically conductive member having a first face region and a second face region elevationally di

A capacitive sensor insertable into a reservoir containing a liquid wherein said liquid undergoes indeterminable variation in contamination and electrical conductivity, said sensor comprising: a first electrically conductive member having a first face region and a second face region elevationally displaced from said first region; a second member of unitary construction including an electrically conductive portion and an electrically insulative portion to isolate electrically said conductive portion from said liquid when said sensor is immersed therein, said second member being in a facing relationship to said first face region to form a first capacitor having a first gap communicating externally of said sensor; and a third member of unitary construction including an electrically conductive portion and an electrically insulative portion to isolate electrically said conductive portion of said third member from said liquid when said sensor is immersed therein, said third member being in a facing relationship to said second face region to form a second capacitor having a second gap communicating externally of said sensor; said sensor being adapted for positioning within said reservoir wherein said liquid entirely fills said first gap and said liquid elevationally varies in said second gap commensurately with said level of said liquid in said reservoir thereby varying capacitance of said second capacitor, such that said level of said liquid in said reservoir may be determined as a function of capacitance of said first capacitor and said second capacitor, said insulative portion of each of said second member and said third member electrically isolating said conductive portion of each of said second member and said third member from electrical conduction through said liquid between said second member and said third member.