US5303167A — Absolute pressure sensor and method

Claim 1

Independent Claim 240 words

Apparatus for determining absolute pressure, P, of a gas comprising: a first microbridge having a first heated element and a thermal sensor thereon, immersed and situated in such proximity to each other and to said gas so as to be thermally coupled by said gas; T g measuring sensor for producing a signal, T g , representative of the temperature of said gas; k and c py computing means for determining thermal conductivity, k, and specific heat, c pv , of said gas using said first microbridge; sensor electronics means for measuring a first current, H I , flowing in said first heated element and producing an electrical signal representative thereof; sensor electronics means for measuring a first voltage, H V , impressed across said first heated element and providing an electrical signal representative thereof; a second microbridge having located thereon a second heated element extending over an etched V-groove; sensor electronics means for measuring a second current, h i flowing in said second heated element and providing an electrical signal representative thereof; sensor electronics means for measuring a second voltage, h v impressed across said second heated element and providing an electrical signal representative thereof; computing means for determining P based on the electrical signals representative of k, c pv , T g H V , H I , h v , and h i ; and output means for providing an output representative of the value of P.

Claim 2

Dependent Claim 240 words

Apparatus for determining absolute pressure, P, of a gas comprising: a first microbridge having a first heated element and a thermal sensor thereon, immersed and situated in such proximity to each other and to said gas so as to be thermally coupled by said gas; T g measuring sensor for producing a signal, T g , representative of the temperature of said gas; k and c py computing means for determining thermal conductivity, k, and specific heat, c pv , of said gas using said first microbridge; sensor electronics means for measuring a first current, H I , flowing in said first heated element and producing an electrical signal representative thereof; sensor electronics means for measuring a first voltage, H V , impressed across said first heated element and providing an electrical signal representative thereof; a second microbridge having located thereon a second heated element extending over an etched V-groove; sensor electronics means for measuring a second current, h i flowing in said second heated element and providing an electrical signal representative thereof; sensor electronics means for measuring a second voltage, h v impressed across said second heated element and providing an electrical signal representative thereof; computing means for determining P based on the electrical signals representative of k, c pv , T g H V , H I , h v , and h i ; and output means for providing an output representative of the value of P.

Claim 3

Dependent Claim 73 words

The apparatus of claim 1 wherein said means for determining P includes periodically deriving a signal utilizing said k, c pv , T g , H I , H V , h i and h v as a measure for said absolute pressure P according to a polynomial of the form: P=♮ A.sub.i (k.sup.n1i c.sub.pv.sup.n2i T.sub.g.sup.n3i H.sub.V.sup.n4i H.sub.I.sup.n5i h.sub.v.sup.n6i h.sub.i.sup.n7i)(3) where A i =constants and n1i, n2i, n3i, n4i, n5i, n6i, and n7i=exponents.

Claim 4

Dependent Claim 56 words

The apparatus of claim 2 further comprising: sensor electronics and microprocessor means for controlling and measuring said H V , H I , h v and h i values; memory means providing said constants and said exponents to said sensor electronics and microprocessor means; and output means providing a signal representative of said absolute pressure P.

Claim 5

Dependent Claim 19 words

The process of claim 3 wherein said exponents n 1i through n 7i in value from -3 to +3.

Claim 6

Dependent Claim 18 words

The apparatus of claim 3 wherein said gas is a fuel gas, air or any other gaseous substance.

Claim 7

Dependent Claim 20 words

The apparatus of claim 5 wherein said exponents n 1i through n 7i range in value from -3 to +3.

Claim 8

Dependent Claim 223 words

Apparatus for determining absolute pressure, P, of a gas when the gas properties of thermal conductivity, k, and specific heat, c pv , are determined by using only the signals of a first microbridge having a proximately positioned first heated element and a thermal sensor both immersed and situated in such proximity to each other and said gas so as to be thermally coupled by said gas, further comprising: sensor electronics means for measuring a first current, H I , flowing in said first heated element; sensor electronics means for measuring a first voltage, H V , impressed across said first heated element; a second microbridge having a second heated element extending over an etched V-groove; sensor electronics means for measuring a second current, h i flowing in said second heated element; sensor electronics means for measuring a second voltage, h v impressed across said second heated element; and computing means for determining P based on k, c pv , T g , H V , H I , h v , and h i according to a polynomial of the form: P=Σ A.sub.i (k.sup.n1i c.sub.pv .sup.n2i T.sub.g .sup.n3i H.sub.V .sup.n4i H.sub.I .sup.n5i h.sub.v .sup.n6i h.sub.i .sup.n7i) where A i =constants and n1i, n2i, n3i, n4i, n5i, n6i, and n7i=exponents; and output means for providing an output representative of the value of P.

Claim 9

Dependent Claim 223 words

Apparatus for determining absolute pressure, P, of a gas when the gas properties of thermal conductivity, k, and specific heat, c pv , are determined by using only the signals of a first microbridge having a proximately positioned first heated element and a thermal sensor both immersed and situated in such proximity to each other and said gas so as to be thermally coupled by said gas, further comprising: sensor electronics means for measuring a first current, H I , flowing in said first heated element; sensor electronics means for measuring a first voltage, H V , impressed across said first heated element; a second microbridge having a second heated element extending over an etched V-groove; sensor electronics means for measuring a second current, h i flowing in said second heated element; sensor electronics means for measuring a second voltage, h v impressed across said second heated element; and computing means for determining P based on k, c pv , T g , H V , H I , h v , and h i according to a polynomial of the form: P=Σ A.sub.i (k.sup.n1i c.sub.pv .sup.n2i T.sub.g .sup.n3i H.sub.V .sup.n4i H.sub.I .sup.n5i h.sub.v .sup.n6i h.sub.i .sup.n7i) where A i =constants and n1i, n2i, n3i, n4i, n5i, n6i, and n7i=exponents; and output means for providing an output representative of the value of P.

Claim 10

Dependent Claim 56 words

The apparatus of claim 7 further comprising: sensor electronics and microprocessor means for controlling and measuring said H V , H I , h v and h i values; memory means providing said constants and said exponents to said sensor electronics and microprocessor means; and output means providing a signal representative of said absolute pressure P.

Claim 11

Dependent Claim 18 words

The apparatus of claim 8 wherein said gas is a fuel gas, air or any other gaseous substance.

Claim 12

Dependent Claim 154 words

A process for the measurement of absolute pressure, P, of a gas, comprising the steps of: conducting a gas into a chamber having a first microbridge and a second microbridge said microbridges being immersed in said gas; measuring the thermal conductivity, k specific heat, c pv , and temperature, T g of said gas at said first microbridge and providing electrical representations thereof; measuring the voltage H V and the current H I of said first microbridge and providing an electrical representation thereof; measuring the voltage h v and the current h i of said second microbridge and providing an electrical representation thereof; deriving a signal for measurement of absolute pressure, P, of said gas according to a polynomial of the form: Σ A.sub.i (k.sup.n1i c.sub.pv.sup.n2i T.sub.g.sup.n3i Hv.sup.n4i H.sub.I.sup.n5i h.sub.v.sup.n6i h.sub.i.sup.n7i) (5 ) where A i =constants, n1i, n2i, n3i, n4i, n5i, n6i, and n7i=exponents; and outputting a representation of the derived value P.

Claim 13

Dependent Claim 154 words

A process for the measurement of absolute pressure, P, of a gas, comprising the steps of: conducting a gas into a chamber having a first microbridge and a second microbridge said microbridges being immersed in said gas; measuring the thermal conductivity, k specific heat, c pv , and temperature, T g of said gas at said first microbridge and providing electrical representations thereof; measuring the voltage H V and the current H I of said first microbridge and providing an electrical representation thereof; measuring the voltage h v and the current h i of said second microbridge and providing an electrical representation thereof; deriving a signal for measurement of absolute pressure, P, of said gas according to a polynomial of the form: Σ A.sub.i (k.sup.n1i c.sub.pv.sup.n2i T.sub.g.sup.n3i Hv.sup.n4i H.sub.I.sup.n5i h.sub.v.sup.n6i h.sub.i.sup.n7i) (5 ) where A i =constants, n1i, n2i, n3i, n4i, n5i, n6i, and n7i=exponents; and outputting a representation of the derived value P.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-04-11	1997-10-11	1998-04-12	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-04-11	2001-10-11	2002-04-12	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-04-11	2005-10-11	2006-04-12	$7700.00	Window Closed / Lapsed

Absolute pressure sensor and method

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