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. 12, 1978
Filed:
Jun. 30, 1977
John T Knepler, Chatham, IL (US);
Dickey-john Corporation, Auburn, IL (US);
Abstract
An air pressure monitor includes an electro-mechanical sensor comprising a flexible diaphragm whose deflection is proportional to the air pressure applied thereto, and a variable inductor including a coil and a movable core inside of the coil, the movable core being attached to the flexible diaphragm for movement in response to the deflection thereof to adjust the inductance of the coil in proportion to the air pressure applied to the diaphragm. The monitor further comprises electrical circuits including a first oscillator circuit including the coil for producing a pressure signal at a frequency proportional to the pressure in response to the inductance of the coil, and a second oscillator circuit for producing a reference signal at a frequency corresponding to the frequency produced by the first oscillator when the pressure is substantially zero. Mixer and filter circuits are provided, connected to the two oscillator circuits for providing a signal whose frequency is proportional to the difference in frequencies between the pressure and reference signals and a Schmitt trigger and divider are connected in series from the filter circuit for producing a chain of digital pulses at a frequency proportional to that of the difference signal. An adjustable gate generator is provided for producing a gate signal having a predetermined period, such that the number of digital pulses produced at the output of the divider during the predetermined period comprises a digital signal corresponding to a measurement in predetermined, fixed units of the pressure at the diaphragm.