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:
May. 31, 1994
Filed:
Dec. 08, 1992
Shiro Nakagawa, Chiba, JP;
Atsuko Tsuchida, Saitama, JP;
TDK Corporation, Tokyo, JP;
Abstract
A humidity meter includes a humidity-frequency converter (2) which is essentially a pulse oscillator, the oscillation frequency of which depends upon the impedance of a humidity sensor (1), a differentiation circuit (3) and a wave-form shaping circuit (4) which essentially operate as a pulse width modulator for adjusting pulse width of an output pulse of the converter (2) for assuring a linear relationship between humidity and the output signal, and an integrator (6) for integrating the output of the pulse width modulator to provide an output signal as a DC level. A feedback path (5) is provided to apply the output signal to the pulse width modulator for assuring a linear output irrespective of the exponential characteristics of the humidity sensor. Said differentiation circuit (3) has a capacitor (31), a first variable impedance element (32) which is controlled by said feedback path , and a second variable impedance element (33) coupled in series with the first variable impedance element (32).