Kavlico Corporation

Combustion Engineering, Inc.

Kaylico Corporation

Besco Industries, Inc.

Bell Microcomponents, Inc.

Robert L Bell

Fred Kavli

Robert Willing

Richard A Lathlaen

A capacitive pressure transducer is comprised of a deflectable diaphragm and a substantially planar reference plate, both preferably molded of ceramic. The diaphragm includes a sensor electrode ring disposed about a central region thereof and a concentric reference electrode ring substantially encompassing the sensor electrode, with a guard ring between the electrodes to electrically isolate the reference electrode from the sensor electrode. The reference plate is disposed in facing relation to the deformable flat surface of the diaphragm and includes a sensor electrode ring disposed and in opposition to the sensor electrode on the diaphragm to form a sensing capacitor therewith. Spacer means disposed in the central region between the diaphragm and the reference plate intercouple the two elements and maintain a substantially fixed dimension in the central region therebetween while permitting deformation of the diaphragm in response to pressure variations. The spacer means is conductive and facilitates electrical connection to the sensor electrode on the reference plate. A cover is disposed about the reference plate and coupled to the periphery of the diaphragm, and includes a reference electrode ring in facing relation to the reference electrode on the diaphragm to form a reference capacitor therewith.

Capacitive pressure transducer

A capacitive pressure transducer is disclosed in which a sensing diaphragm bearing an electrode is mounted to flex in response to applied fluid pressure relative to a reference member having an opposed electrode. A thin film or layer of dielectric material such as glass covers the reference member electrode and has formed therein a concavity matching the flexed curvature of the sensing diaphragm at its limit position. The dielectric layer has a high compressive strength and substantially enhances linearity by providing a substantially higher capacitance than the equivalent fluid-filled space. The transducer is retained within a transducer assembly under compressive preload, the assembly further including thermal strain relief means. Also disclosed are methods of making the transducer, which methods include thick film screen deposition techniques for forming concavities having preselected contours in the dielectric layer.

High accuracy differential pressure capacitive transducer and methods

High accuracy differential pressure capacitive transducer

A capacitive pressure transducer comprising a pair of disc shaped members having planar surfaces made from an insulator material, one of the members being several times thinner than the other plate and flexible and constituting a diaphragm and the other thicker plate constituting a stationary plate. A thin conductive film is formed on the surface of each of the members to form the plates of the capacitor. A glass frit is applied on the marginal edge of each member and when the members are held in adjacent relationship, the assembly is fired to seal the two members together while spacing them a predetermined distance apart so that the two conductive plates are opposite each other and are separated by an open gap of a predetermined distance, the two conductive plates being insulated one from the other. Leads are electrically connected to the conductive plate of each disc through the fused glass frit. When pressure is applied to the member, the diaphragm member is displaced thereby changing the capacitance of the pressure transducer.

Capacitive pressure transducer and method of making same

A differential capacitive force responsive transducer provides a substantially linear relationship between transducer output and input variations. A pressure or load to be measured is applied to one surface of a deflectable diaphragm, the opposite surface of which includes at least a pair of electrodes at different positions, such that when the diaphragm flexes there is a differential deflection of the electrodes. A substantially rigid electrode-bearing plate is secured to the electrode-bearing face of the diaphragm by a spacer or spacers in an intermediate flexure region of the diaphragm, to define separate capacitive elements with the diaphragm electrodes. The plate thus moves with the diaphragm, maintaining a fixed spacing at the spacer elements, but with the spacings between the elements varying in opposite senses. With this construction, the transducer can be of low cost, small size, precision manufacture, and use readily deposited thick or thin film electrodes. Moreover the circuits may automatically be adjusted to provide selected nominal zero and range values, so that the transducer can be utilized interchangeably with other transducers in mass production systems. Furthermore, the differential capacitance values obtained from a single transducer can directly provide digital values to a processor, by oppositely varying two variable frequency oscillators, and using the difference frequency to generate pulse counts during successive time intervals.

Force responsive transducer

A capacitive pressure transducer comprising a pair of disc shaped members having planar surfaces made from an insulator material, one of the members being several times thinner than the other plate and flexible and constituting a diaphragm and the other thicker plate constituting a stationary plate. A thin conductive film is formed on the surface of each of the members to form the plates of the capacitor. A glass frit is applied on the marginal edge of each member and when the members are held in adjacent relationship, the assembly is fired to seal the two members together while spacing them a predetermined distance apart so that the two cnductive plates are opposite each other and are separated by an open gap of a predetermined distance, the two conductive plates being insulated one from the other. Leads are electrically connected to the conductive plate of each disc through the fused glass frit. When pressure is applied to the member, the diaphragm member is displaced thereby changing the capacitance of the pressure transducer.

Capacitive pressure transducer with cut out conductive plate

A capacitive pressure transducer comprising a pair of thin discs made from an insulator, a thin metal film metalized onto each of the discs and forming the plates of the capacitor, and means for bonding the two discs together such that the two metal films are opposite each other, the two metal films are separated by an open gap, and the two metal films are insulated one from the other. When pressure is applied to the discs, the discs are displaced thereby changing the capacitance of the pressure transducer.

An electrode for use in capacitive pressure transducers of the type including either a single diaphragm electrode and a conductive reference plate separated by a gap or two diaphragm electrodes separated by a gap. The electrode comprises a conductive area having a plurality of nonconductive areas in the conductive area arranged and configured such that the capacitive fringe effects of the nonconductive areas substantially reduces the nonlinear component of the variation in the capacitance of the capacitive pressure transducer as a function of pressure.

Capacitive pressure transducer with improved electrode

A capacitive pressure transducer including a pair of electrically insulative elastic diaphragms disposed adjacent each other and bonded together in a spaced apart relationship to form a sealed cavity, a conductive layer applied to the inside surface of each of the diaphragms and a small absolute pressure provided in the cavity. This small absolute pressure cavity essentially reduces the effects of the negative temperature coefficient of the modulus of elasticity of the diaphragms.

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Chatsworth, CA, United States of America

Robert L Bell