Pressure sensor
First Claim
1. A pressure sensor for measuring the pressure of a fluid, said pressure sensor comprising:
- a base formed of ceramic material having a front surface and a back surface opposite said front surface;
an elastically deformable diaphragm made of ceramic material secured to said base front surface so as to be spaced apart a predetermined distance from said base front surface to define a pressure chamber therebetween, said diaphragm having an inner surface that partially defines said pressure chamber and a pressure face opposite said inner surface which is exposed to the fluid;
a plurality of electrodes provided on said base front surface, said base electrodes including a center electrode and an outer ring electrode, said outer ring electrode being spaced apart from and completely surrounding said center electrode;
a diaphragm electrode attached to said diaphragm inner surface so as to form a capacitor with said base center electrode;
a capacitance measuring circuit for measuring the capacitance across said base center electrode and said diaphragm electrode so as to produce an output signal based on said measured capacitance that is representative of the pressure of the fluid; and
a first conductor connected between said base center electrode and said capacitance measuring circuit, a second conductor connected between said diaphragm electrode and said capacitance measuring circuit and a third conductor connected between said base outer ring electrode and said capacitance measuring circuit, wherein said capacitance measuring circuit is configured to apply signals through said first and second conductors to measure said base center electrode-diaphragm electrode capacitance and to apply a signal to said outer ring electrode through said third conductor to hold said outer ring electrode at a constant voltage.
1 Assignment
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Accused Products
Abstract
A pressure sensor of electrostatic capacitance type is disclosed, which detects the pressure of a measurement fluid acting on a pressured surface of an elastic diaphragm from a change in the electrostatic capacitance between opposed electrodes provided on opposed surface of a ceramic base and the elastic diaphragm. The base side electrode comprises a plurality of division electrode one enclosing the next inner one. Of these division electrodes the outermost one is grounded or held at a predetermined voltage, or it is covered by overcoat glass, and thus it is imparted with a function of stabilizing the measurement value. In an electrode hole for leading an electrode to the outside, a path is formed for leading atmospheric air or like fluid providing for the reference pressure for pressure measurement into the space defined between the base and elastic diaphragm.
35 Citations
21 Claims
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1. A pressure sensor for measuring the pressure of a fluid, said pressure sensor comprising:
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a base formed of ceramic material having a front surface and a back surface opposite said front surface; an elastically deformable diaphragm made of ceramic material secured to said base front surface so as to be spaced apart a predetermined distance from said base front surface to define a pressure chamber therebetween, said diaphragm having an inner surface that partially defines said pressure chamber and a pressure face opposite said inner surface which is exposed to the fluid; a plurality of electrodes provided on said base front surface, said base electrodes including a center electrode and an outer ring electrode, said outer ring electrode being spaced apart from and completely surrounding said center electrode; a diaphragm electrode attached to said diaphragm inner surface so as to form a capacitor with said base center electrode; a capacitance measuring circuit for measuring the capacitance across said base center electrode and said diaphragm electrode so as to produce an output signal based on said measured capacitance that is representative of the pressure of the fluid; and a first conductor connected between said base center electrode and said capacitance measuring circuit, a second conductor connected between said diaphragm electrode and said capacitance measuring circuit and a third conductor connected between said base outer ring electrode and said capacitance measuring circuit, wherein said capacitance measuring circuit is configured to apply signals through said first and second conductors to measure said base center electrode-diaphragm electrode capacitance and to apply a signal to said outer ring electrode through said third conductor to hold said outer ring electrode at a constant voltage. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A pressure sensor for measuring the pressure of a fluid, said sensor comprising:
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a base formed of ceramic material having a front surface and a back surface opposite said front surface; an elastically deformable diaphragm made of ceramic material secured to said base front surface so as to be spaced apart a predetermined distance from said front surface so as to define a pressure chamber therebetween, said diaphragm having an inner surface that partially defines said pressure chamber and a pressure face opposite said inner surface which is exposed to the fluid; a plurality of electrodes provided on said base front surface, said base electrodes include a center electrode and an outer ring electrode, said outer ring electrode spaced apart from and completely surrounding said center electrode; a diaphragm electrode attached to said diaphragm inner surface so as to form a capacitor with at least said base center electrode; a capacitance measuring circuit for measuring the capacitance across said base center electrode and said diaphragm electrode so as to produce an output signal based on said measured capacitance that is representative of the pressure of the fluid; a first conductor connected between said base center electrode and said capacitance measuring circuit and a second conductor connected between said diaphragm electrode and said capacitance measuring circuit and a third conductor connected between said base outer ring electrode and said capacitance measuring circuit; and an insulating glass layer positioned to at least partially cover said base outer ring electrode. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A pressure sensor for measuring the pressure of a fluid, said pressure sensor comprising:
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a main body including a ceramic base formed with a front surface and a back surface opposite said front surface; a ceramic, elastically deformable diaphragm coupled to and spaced from said ceramic base front surface so as to define a pressure chamber therebetween, said diaphragm having an inner surface that defines said pressure chamber and a pressure face opposite said inner surface that is exposed to the fluid, said diaphragm being elastically deformable as a function of the pressure applied thereto; at least one measuring electrode disposed on said ceramic base front surface, a shield electrode disposed on said ceramic base front surface, said shield electrode being spaced away from and circumferentially surrounding said at least one measuring electrode, and a common electrode disposed on said diaphragm inner surface; conductive members that extend through said ceramic base from said at least one measuring electrode, said shield electrode, and said common electrode to said ceramic base back surface, each said conductive member terminating at a conductive terminal on said ceramic base back surface; a signal processing circuit connected to said electrodes and located on said ceramic base back surface, said signal processing circuit being configured to apply a stimuli signal across said at least one measuring electrode and said common electrode, to measure a response from said electrodes to said stimuli signal and to generate an output signal based on said measured response that is a function of the pressure of the fluid and to hold said shield electrode at a constant voltage; and a conductive pattern formed on said ceramic base back surface, said conductive pattern including a plurality of conductive traces for connecting said conductive member terminals to said signal processing circuit, wherein said conductive member terminal associated with said shield electrode is connected to a conductive trace positioned on said ceramic base back surface that separates said conductive member terminal to which said measuring electrode is connected from said conductive member terminal to which said common electrode is connected. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification