The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 04, 1991
Filed:
Mar. 07, 1989
Dennis P Sarr, Kent, WA (US);
Patrick L Anderson, Bellevue, WA (US);
The Boeing Company, Seattle, WA (US);
Abstract
A distance-measuring apparatus for measuring the distance between a capacitance-type sensing probe (60) and a nearby surface of a conductive body is provided. A probe (60) includes a plurality of measuring electrodes (56.sub.l -56.sub.n) and a grounding electrode (58). The grounding electrode protrudes from the probe and grounds the nearby surface of the conductive body. A control system (10) is connected to the probe (60). A processor (12) issues control instructions, S.sub.CTL, to a selector (16). The selector (16) selects one of a plurality of measuring electrodes (56.sub.l -56.sub.n) and connects the selected electrode to a converter (14). A charging circuit (18) applies a charging voltage to the selected electrode, causing a capacitor formed by the selected electrode and the nearby surface of the conductive body to charge up. A timing circuit (22) starts a counter (32) when one of the measuring electrodes (56.sub.l -56.sub.n) is selected and stops the counter (32) when a capacitor charge voltage, V'.sub.C, becomes greater than or equal to a threshold voltage, V.sub.T. The counter (32) counts clock pulses, V.sub.CK, produced by a clock (34) and produces a count value, S.sub.CNT, that is proportional to the charge time of the capacitor. The processor (12) translates the S.sub.CNT value into a distance value corresponding to the distance between the sensing probe (60) and the nearby surface of the body being inspected.