Inductive pressure sensor using two oscillators

Claim 2

A compact, temperature-compensated inductive pressure sensor having first (15) and second (22) substantially identical, thermally coupled but otherwise independent oscillator circuits, each including an inductance coil (13,20), and each producing an output signal (f1,f2); a mixer (23) connected to said oscillator circuits for producing a frequency difference signal which is a predetermined function of the output signals of said oscillator circuits; wherein, in accordance with the invention, said first oscillator (15) includes a variable inductance electromagnetically responsive to the position of a diaphragm, said diaphragm forming a part of a pressure measurement chamber (11); said second oscillator (22) includes a variable inductance electromagnetically responsive to the position of a diaphragm, said diaphragm forming a part of a reference pressure chamber (18); said coils (13,20), forming a part of said oscillator circuits (15,22), are formed as flat films, and at least one (13) of said inductance coils is a variable inductance, said compact pressure sensor including a diaphragm (12) disposed at a variable distance (d1) from said one coil (13), said diaphragm (12) being deflectable in accordance with the pressure (p1) to be sensed and having a layer of material (12) thereon which affects the inductance of the coil (13), and whose deflection thereby affects the frequency of the output signal (f1) of the oscillator circuit (15) of which it forms a part.

Claim 3

The compact pressure sensor of claim 1, wherein said inductance-affecting material is a ferrite.

Claim 4

The compact pressure sensor of claim 1, wherein said inductance-affecting material is a highly conductive material.

Claim 5

The compact pressure sensor of claim 1, wherein the pressure of said reference pressure is ambient air pressure.

Claim 6

The compact pressure sensor of claim 1, wherein the pressure of said reference pressure chamber is an absolute pressure in a sealed chamber.

Claim 7

The compact pressure sensor of claim 1, wherein first (15) and second (22) oscillator circuits are provided, disposed spatially so close together that they are exposed to the same ambient temperature, said first oscillator (15) includes a variable inductance electromagnetically responsive to the position of a diaphragm, said diaphragm forming a part of a first pressure measurement chamber (11), and said second oscillator (22) includes a variable inductance electromagnetically responsive to the position of a diaphragm, said diaphragm forming a part of a second pressure measurement chamber (18), to permit differential-pressure measurements between two media.

Claim 8

The compact pressure sensor of claim 1, wherein first (15) and second (22) oscillator circuits are provided, disposed spatially so close together that they are exposed to the same ambient temperature, said first oscillator (15) includes a variable inductance electromagnetically responsive to the position of a diaphragm, said diaphragm forming a part of a pressure measurement chamber (11), and the inductance of said second oscillator (22) is fixed, so as to limit the frequency drift of said second oscillator to that caused by temperature fluctuations, and to permit compensation of said frequency difference signal for such temperature fluctuations.

Claim 9

A pressure sensing system, in combination with the induction pipe of an automotive internal combustion engine (I.C.E.), comprising at least two substantially identical, thermally coupled but otherwise independent oscillator circuits (15,22), each including an inductance coil (13,20), and each producing an output signal (f 1 ,f 2 ); a mixer (23) connected to said oscillator circuits for producing a frequency difference signal which is a predetermined function of the output signals of said oscillator circuits; wherein, in accordance with the invention, said coils (13,20), forming a part of said oscillator circuits (15,22), are formed as flat films, and at least one (13) of said inductance coils is a variable inductance, said compact pressure sensor including a diaphragm (12) disposed at a variable distance (d 1 ) from said one coil (13), said diaphragm (12) being deflectable in accordance with the pressure (p 1 ) to be sensed and having a layer of material (12) thereon which affects the inductance of the coil (13), and whose deflection thereby affects the frequency of the output signal (f 1 ) of the oscillator circuit (15) of which it forms a part.

Claim 10

A pressure sensing system, in combination with the induction pipe of an automotive internal combustion engine (I.C.E.), comprising at least two substantially identical, thermally coupled but otherwise independent oscillator circuits (15,22), each including an inductance coil (13,20), and each producing an output signal (f 1 ,f 2 ); a mixer (23) connected to said oscillator circuits for producing a frequency difference signal which is a predetermined function of the output signals of said oscillator circuits; wherein, in accordance with the invention, said coils (13,20), forming a part of said oscillator circuits (15,22), are formed as flat films, and at least one (13) of said inductance coils is a variable inductance, said compact pressure sensor including a diaphragm (12) disposed at a variable distance (d 1 ) from said one coil (13), said diaphragm (12) being deflectable in accordance with the pressure (p 1 ) to be sensed and having a layer of material (12) thereon which affects the inductance of the coil (13), and whose deflection thereby affects the frequency of the output signal (f 1 ) of the oscillator circuit (15) of which it forms a part.

Claim 11

The pressure sensing system of claim 8, wherein said inductance-affecting material is a ferrite.

Claim 12

The pressure sensing system of claim 8, wherein said inductance-affecting material is a highly conductive material.

Claim 13

A compact, temperature-compensated inductive pressure sensor having a least first and second substantially identical, thermally coupled but otherwise independent oscillator circuits (15,22), each including an inductance coil (13,20), and each producing an output signal (f 1 ,f 2 ); a mixer (23) connected to said oscillator circuits for producing a frequency difference signal which is a predetermined function of the output signals of said oscillator circuits; wherein, in accordance with the invention, said coils (13,20), forming a part of said oscillator circuits (15,22), are formed as flat films, and are variable inductances, each electromagnetically responsive to the position of a respective diaphragm (12,19), each of said diaphragms (12,19) being respectively disposed at a variable distance (d 1 ,d 2 ) from its respective coil (13,20), a first one (12) of said diaphragm forming a part of a pressure measurement chamber (11), being deflectable in accordance with the pressure (p 1 ) to be sensed and having a layer of material (12) thereon which affects the inductance of its coil (13), and whose deflection thereby affects the frequency of the output signal (f 1 ) of said first oscillator circuit (15) of which it forms a part, and a second one (19) of said diaphragm forming a part of a reference pressure chamber (18), being deflectable in accordance with the reference pressure (p 2 ) therein and having a layer of material (19) on said diaphragm which affects the inductance of its coil (20), and whose deflection thereby affects the frequency of the output signal (f 2 ) of said second oscillator circuit (22) of which it forms a part.

Claim 14

A compact, temperature-compensated inductive pressure sensor having a least first and second substantially identical, thermally coupled but otherwise independent oscillator circuits (15,22), each including an inductance coil (13,20), and each producing an output signal (f 1 ,f 2 ); a mixer (23) connected to said oscillator circuits for producing a frequency difference signal which is a predetermined function of the output signals of said oscillator circuits; wherein, in accordance with the invention, said coils (13,20), forming a part of said oscillator circuits (15,22), are formed as flat films, and are variable inductances, each electromagnetically responsive to the position of a respective diaphragm (12,19), each of said diaphragms (12,19) being respectively disposed at a variable distance (d 1 ,d 2 ) from its respective coil (13,20), a first one (12) of said diaphragm forming a part of a pressure measurement chamber (11), being deflectable in accordance with the pressure (p 1 ) to be sensed and having a layer of material (12) thereon which affects the inductance of its coil (13), and whose deflection thereby affects the frequency of the output signal (f 1 ) of said first oscillator circuit (15) of which it forms a part, and a second one (19) of said diaphragm forming a part of a reference pressure chamber (18), being deflectable in accordance with the reference pressure (p 2 ) therein and having a layer of material (19) on said diaphragm which affects the inductance of its coil (20), and whose deflection thereby affects the frequency of the output signal (f 2 ) of said second oscillator circuit (22) of which it forms a part.