US6430985B1
Expired / Lapsed
US
⏱️ 0.0 years remaining
Multiple point calibrated HVAC flow rate controller
Assignee: Johnson Controls Technology Co
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Filing: 1999-08-05
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Granted: 2002-08-13
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Expires: 2019-08-05
Abstract
Abstract A pressure sensor often is employed to provide an indication of a pressure differential that results from air flowing through an HVAC system. An apparatus processes the pressure differential indication to derive a measurement of the air flow rate. Greater measurement accuracy is achieved by calibrating the apparatus at both the minimum and maximum flow rates expected in the system. This is accomplished by deriving separate gain factor coefficients for the performance of the sensing at both the minimum and maximum flow rates. The use of these coefficients also eliminates the dependency of the flow rate calculation on the density of the fluid and the cross-sectional area of the fluid conduit.
Inventors
- 👤 Kirk H Drees
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 07:13
CPC Classifications
G; G01; G01F; G01F1/00; G01F1/05; G01F1/34; G01F1/36; G01F1/363
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
157 words
A method for calibrating an apparatus which measures an unknown flow rate of a fluid using a pressure sensor, said method comprising: causing the fluid to flow past the pressure sensor at a first rate; obtaining a first pressure reading from the pressure sensor; measuring the flow of fluid with a flow rate meter to produce a first flow rate measurement; causing the fluid to flow past the pressure sensor at a second rate; obtaining a second pressure reading from the pressure sensor; measuring the flow of fluid with a flow rate meter to produce a second flow rate measurement; calculating a first gain factor coefficient a 0 from the first pressure reading, the second pressure reading, the first flow rate measurement and the second flow rate measurement; and calculating a second gain factor coefficient a 1 from the first pressure reading, the second pressure reading, the first flow rate measurement and the second flow rate measurement.
Claim 2
Independent Claim
157 words
A method for calibrating an apparatus which measures an unknown flow rate of a fluid using a pressure sensor, said method comprising: causing the fluid to flow past the pressure sensor at a first rate; obtaining a first pressure reading from the pressure sensor; measuring the flow of fluid with a flow rate meter to produce a first flow rate measurement; causing the fluid to flow past the pressure sensor at a second rate; obtaining a second pressure reading from the pressure sensor; measuring the flow of fluid with a flow rate meter to produce a second flow rate measurement; calculating a first gain factor coefficient a 0 from the first pressure reading, the second pressure reading, the first flow rate measurement and the second flow rate measurement; and calculating a second gain factor coefficient a 1 from the first pressure reading, the second pressure reading, the first flow rate measurement and the second flow rate measurement.
Claim 3
Dependent Claim
21 words
The method as recited in claim 1 wherein the first pressure reading and the second pressure reading are differential pressure readings.
Claim 4
Dependent Claim
112 words
The method as recited in claim 1 wherein the second gain factor coefficient a 1 is calculated according to the expression: a 1 = ( C · A ) 2 ( P 2 - P 1 ) · ( P 2 ω . 2 2 - P 1 ω . 1 2 ) where C is a coefficient related to the fluid density, A is the cross-sectional area of a conduit through which the fluid is flowing, P 1 is the first pressure reading, P 2 is the second pressure reading, {dot over (ω)} 1 is the first flow rate measurement, and {dot over (ω)} 2 is the second flow rate measurement.
Claim 5
Dependent Claim
41 words
The method as recited in claim 3 wherein the first gain factor coefficient a 0 is calculated according the expression: a 0 = P 1 [ ( C · A ω . 1 ) 2 - a 1 ] .
Claim 6
Dependent Claim
84 words
The method as recited in claim 1 wherein the second gain factor coefficient a 1 is calculated according to the expression: a 1 = 1 ( P 2 - P 1 ) · ( P 2 ω . 2 2 - P 1 ω . 1 2 ) where P 1 is the first pressure reading, P 2 is the second pressure reading, {dot over (ω)} 1 is the first flow rate measurement, and {dot over (ω)} 2 is the second flow rate measurement.
Claim 7
Dependent Claim
39 words
The method as recited in claim 5 wherein the first gain factor coefficient a 0 is calculated according the expression: a o = P 1 · [ ( 1 ω . 1 ) 2 - a 1 ] .
Claim 8
Dependent Claim
59 words
The method as recited in claim 1 further comprising using the apparatus to determine an unknown flow rate of the fluid using the expression: ω . = Z · Δ P a 0 + a 1 * Δ P where Z has a predefined value, ΔP is a pressure differential derived from the pressure sensor.
Claim 9
Dependent Claim
11 words
The method as recited in claim 7 wherein Z equals one.
Claim 10
Dependent Claim
31 words
The method as recited in claim 7 wherein Z equals the product of a coefficient of fluid density and a cross-sectional area of a conduit through which the fluid is flowing.
Claim 11
Independent Claim
243 words
A method for measuring a flow rate of a fluid using an apparatus having a pressure sensor, said method comprising: calibrating the apparatus by: (a) causing the fluid to flow past the pressure sensor at a first rate, (b) obtaining a first differential pressure reading ΔP 1 from the pressure sensor, (c) measuring the flow of fluid with a flow rate meter to produce a first flow rate measurement {dot over (ω)} 1 , (d) causing the fluid to flow past the pressure sensor at a second rate, (e) obtaining a second differential pressure reading ΔP 2 from the pressure sensor, measuring the flow of fluid with a flow rate meter to produce a second flow rate measurement {dot over (ω)} 2 , (f) calculating a first gain factor coefficient a 0 from the first pressure reading, the second pressure reading, the first flow rate measurement and the second flow rate measurement, and (g) calculating a second gain factor coefficient a 1 from the first pressure reading, the second pressure reading, the first flow rate measurement and the second flow rate measurement; and thereafter using the pressure sensor to measure a pressure differential ΔP as the fluid flows past the pressure sensor at the unknown flow rate; producing a flow rate value {dot over (ω)} using the expression: ω . = Z · Δ P a 0 + a 1 * Δ P where Z has a predefined value.
Claim 12
Independent Claim
243 words
A method for measuring a flow rate of a fluid using an apparatus having a pressure sensor, said method comprising: calibrating the apparatus by: (a) causing the fluid to flow past the pressure sensor at a first rate, (b) obtaining a first differential pressure reading ΔP 1 from the pressure sensor, (c) measuring the flow of fluid with a flow rate meter to produce a first flow rate measurement {dot over (ω)} 1 , (d) causing the fluid to flow past the pressure sensor at a second rate, (e) obtaining a second differential pressure reading ΔP 2 from the pressure sensor, measuring the flow of fluid with a flow rate meter to produce a second flow rate measurement {dot over (ω)} 2 , (f) calculating a first gain factor coefficient a 0 from the first pressure reading, the second pressure reading, the first flow rate measurement and the second flow rate measurement, and (g) calculating a second gain factor coefficient a 1 from the first pressure reading, the second pressure reading, the first flow rate measurement and the second flow rate measurement; and thereafter using the pressure sensor to measure a pressure differential ΔP as the fluid flows past the pressure sensor at the unknown flow rate; producing a flow rate value {dot over (ω)} using the expression: ω . = Z · Δ P a 0 + a 1 * Δ P where Z has a predefined value.
Claim 13
Dependent Claim
98 words
The method as recited in claim 10 wherein the second gain factor coefficient a 1 is calculated according to the expression: a 1 = Z ( Δ P 2 - Δ P 1 ) · ( Δ P 2 ω . 2 2 - Δ P 1 ω . 1 2 ) where P 1 is the first differential pressure reading, P 2 is the second differential pressure reading, {dot over (ω)} 1 is the first flow rate measurement, and {dot over (ω)} 2 is the second flow rate measurement.
Claim 14
Dependent Claim
43 words
The method as recited in claim 11 wherein the first gain factor coefficient a 0 is calculated according to the expression: a 0 = Δ P 1 · [ ( Z ω . 1 ) 2 - a 1 ] .
Claim 15
Dependent Claim
11 words
The method as recited in claim 12 wherein Z equals one.
Claim 16
Dependent Claim
31 words
The method as recited in claim 12 wherein Z equals the product of a coefficient of fluid density and a cross-sectional area of a conduit through which the fluid is flowing.
Claim 17
Independent Claim
146 words
A method for calibrating an apparatus which measures an unknown flow rate of a fluid using a pressure sensor, said method comprising: causing the fluid to flow past the pressure sensor at a first rate; obtaining a first pressure reading from the pressure sensor; measuring the flow of fluid with a flow rate meter to produce a first flow rate measurement; causing the fluid to flow past the pressure sensor at a second rate; obtaining a second pressure reading from the pressure sensor; measuring the flow of fluid with a flow rate meter to produce a second flow rate measurement; deriving a first coefficient for a gain factor in response to the first pressure reading and the second pressure reading measured by the pressure sensor; and deriving a second coefficient for a gain factor in response to the first pressure reading and the second pressure reading.
Claim 18
Independent Claim
146 words
A method for calibrating an apparatus which measures an unknown flow rate of a fluid using a pressure sensor, said method comprising: causing the fluid to flow past the pressure sensor at a first rate; obtaining a first pressure reading from the pressure sensor; measuring the flow of fluid with a flow rate meter to produce a first flow rate measurement; causing the fluid to flow past the pressure sensor at a second rate; obtaining a second pressure reading from the pressure sensor; measuring the flow of fluid with a flow rate meter to produce a second flow rate measurement; deriving a first coefficient for a gain factor in response to the first pressure reading and the second pressure reading measured by the pressure sensor; and deriving a second coefficient for a gain factor in response to the first pressure reading and the second pressure reading.
Claim 19
Dependent Claim
91 words
The method as recited in claim 15 wherein the second gain factor coefficient a 1 is calculated according the expression: a 1 = 1 ( P 2 - P 1 ) · ( P 2 ω . 2 2 - P 1 ω . 1 2 ) where P 1 is the first pressure reading at the first flow rate, P 2 is the second pressure reading at the second flow rate, {dot over (ω)} 1 is the first flow rate, and {dot over (ω)} 2 is the second flow rate.
Claim 20
Dependent Claim
39 words
The method as recited in claim 16 wherein the first gain factor coefficient a 0 is calculated according the expression: a o = P 1 · [ ( 1 ω . 1 ) 2 - a 1 ] .
Claim 21
Dependent Claim
21 words
The method as recited in claim 15 wherein the first coefficient is derived in response to the first flow rate measurement.
Claim 22
Dependent Claim
27 words
The method as recited in claim 18 wherein the second coefficient is derived in response to the first flow rate measurement and the second flow rate measurement.
Claim 23
Dependent Claim
15 words
The method of claim 15 wherein the fluid is air used in an HVAC system.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2005-08-12 | 2006-02-11 | 2006-08-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2009-08-12 | 2010-02-11 | 2010-08-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2013-08-12 | 2014-02-11 | 2014-08-13 | $7700.00 | Window Closed / Lapsed |