Patent ID: 6239601
Filing Date: 2001-05-29
Classification: B64D,G01B

Abstract:
An apparatus, comprising:a first total impedance sensor for sensing total impedance changes due to the presence of an accumulated material on an outer surface of an object;a first total impedance measuring circuit coupled to said first total impedance sensor for producing output voltages based on said total impedance changes sensed by said first total impedance sensor when said first total impedance measuring circuit is operated at a first frequency and a second frequency when said surface is dry and when said surface is covered by the accumulated material, said first frequency and said second frequency both being in a range wherein the dielectric constant and conductivity of the accumulated material vary slightly from said first frequency to said second frequency;a second total impedance sensor for sensing total impedance changes due to the presence of the accumulated material;a second total impedance measuring circuit coupled to said second total impedance sensor for producing output voltages based on said total impedance changes sensed by said second total impedance sensor when said second total impedance measuring circuit is operated at said first frequency and said second frequency when said surface is dry and when said surface is covered by the accumulated material; anda processor coupled to said first total impedance measuring circuit and said second total impedance measuring circuit for calculating an output value using said output voltages produced by said first total impedance measuring circuit and said second total impedance measuring circuit, wherein said output value is used to determine the thickness of the accumulated material.