The present invention relates to sensor plates forming an acoustic channel vibrated with ultrasonic energy, and which can be used for detection of contaminants, such as ice on a surface on the plate.
Detection of contaminants on surfaces, such as ice on the wings of an aircraft, has generally been done with various types of probes or sensors that detect the ice only at specific locations. Two types of ice detectors are shown in U.S. Pat. Nos. 4,980,673, and 3,277,459. U.S. Pat. No. 4,980,673 discloses a magnetostrictive resonance damping sensor while U.S. Pat. No. 3,277,459 shows a sensor which works on sensing heat of transformation.
In addition, mechanical scrapers have been used for measuring ice build up by scraping a target and determining the ice removal. The change in optical index of refraction of a surface has been used for determining when a surface has become coated with ice, by comparing the measured index to the index when the surface was uncoated. Other types of sensors used for ice detection include radiation absorption detectors, capacitive ice detectors, conductivity ice detectors, the damping of piezoelectric vibrating elements, and resonance damping of magnetostrictive elements. A vibrating ice detector that utilizes a non intrusive surface is illustrated in U.S. Pat. No. 4,611,492.
Most of the ice detectors described above detect ice at a single point, while accumulation in different portions of a surface can go undetected. Further, the sensors generally are spaced from wing surfaces of the aircraft. Most sensors also significantly increase drag and weight.