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:
Jan. 25, 1994
Filed:
Jun. 17, 1991
Earl B Hoekman, Roseville, MN (US);
Samuel Bernard, Jr, Vadnais Heights, MN (US);
Minnesota Mining and Manufacturing Company, St. Paul, MN (US);
Abstract
A vehicle detector includes one or more inductive sensors connected to an oscillator circuit. A timing circuit defines a plurality of sequential measurement frame segments. The oscillator circuit is coupled to an inductive sensor during each of the measurement frame segments. The time duration of each of the plurality of measurement frame segments is measured. After the completion of each frame segment for a particular inductive sensor, a total measurement frame time duration for that sensor is calculated based upon durations of a predetermined number of measurement frame segments for that sensor. The total measurement frame time duration and a reference time duration are compared and a difference is determined. If the difference between the total measurement frame time duration and the reference time duration exceeds a threshold value, an output signal indicative of the presence of a vehicle in the vicinity of the inductive sensor is generated.