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:
Sep. 07, 1993
Filed:
Sep. 13, 1989
Fred B Holt, Seattle, WA (US);
David I Feinstein, Seattle, WA (US);
The Boeing Company, Seattle, WA (US);
Abstract
A method for processing data produced by a chemical sensor to predict a rate of diffusion and steady-state level of a chemical vapor absorbed by a coating applied to the chemical sensor. A chemical sensor (10) includes a surface acoustic wave device (12) in which a polymer coating (34) is provided to absorb a chemical vapor. As the vapor is absorbed by the polymer coating, a resonant frequency associated with the SAW device changes in proportion to the mass of the vapor absorbed. The change in resonant frequency is periodically sampled by a high-speed counter (58), digitized, and filtered by a microprocessor (100). In processing the filtered data, the microprocessor describes each data point as a constraint line in a (.tau.,C) space, where .tau. corresponds to the rate of diffusion of the chemical vapor into the polymer and C corresponds to the concentration of the chemical vapor in the polymer at a time t. A minimum energy function L(.tau.,C) is determined for successive groups of constraint lines, eventually enabling final values for both .tau. and C to be predicted. The predicted values are used to detect and identify the chemical vapor to which the chemical sensor is exposed, well before the concentration of the chemical vapor in the polymer reaches a steady-state level.