Inductive pressure sensor using two oscillators

US4536719A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Helmut Baum · Stuttgart, DE
• Heinz Pfizenmaier · Leonberg, DE
• Ewald Schmidt · Ludwigsburg, DE
• Franz Strauss · Stuttgart, DE

Key dates

• Filing date: Jan 28, 1982
• Grant date: Aug 20, 1985
• Expiry date: Jan 28, 2002

Classification

• Technology area (CPC G): Physics
• CPC primary: G01L9/007
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

An inductive pressure sensor is proposed which has at least one coil embodying a frequency-determining part of an oscillator and disposed at a distance from a diaphragm which is deflectable in accordance with pressure. When pressure is exerted on the diaphragm, the inductance of the coil and thus the oscillator frequency are shifted. The coil is a flat, spiral element and the diaphragm has a surface of highly conductive or ferrite material. It is further provided that two oscillators of identical design and having corresponding coils are used, operating under identical thermal conditions. Either one oscillator operates at a fixed frequency, so that both absolute-pressure measurements and differential-pressure measurements relative to ambient pressure can be made, or else the two oscillators can be detunable in accordance with pressure, so that differential-pressure measurements between two media can be made. The output signal is then obtained by mixing. The oscillators are preferably embodied as thin-film elements.