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:
Nov. 10, 1987
Filed:
Sep. 19, 1986
Applicant:
Inventor:
William H Gross, Sunnyvale, CA (US);
Assignee:
National Semiconductor Corporation, Santa Clara, CA (US);
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
G06G / ;
U.S. Cl.
CPC ...
307519 ; 307529 ; 307525 ; 307512 ; 328144 ; 328158 ; 324166 ;
Abstract
A tachometer circuit is described that has a zero ripple d-c output that is directly proportional to the frequency. The circuit includes a pair of full wave rectifiers to act upon the sine and cosine signal inputs. The rectified currents are first squared, then summed together and finally the square root is taken. Since the quantity .sqroot.sine.sup.2 +cosine.sup.2 is a constant, there is no ripple and no output filtering is required to eliminate ripple. This means that the output can follow very rapid changes in frequency and no lag is introduced by the inclusion of low pass signal filtering.