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US4734873A
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Method of digital process variable transmitter calibration and a process variable transmitter system utilizing the same
Assignee: Honeywell Inc
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Filing: 1986-07-18
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Granted: 1988-03-29
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Expires: 2006-07-18
Abstract
Abstract A method of digital process variable transmitter calibration includes the steps of sensing the process variable (PV) to produce an analog output which is converted to a digital signal representation. The digital signal is corrected by a microprocessor using a characterization equation previously individually developed during a manufacturing testing of the process variable transmitter over a predetermined range of environmental stimuli to ascrtain the coefficients for a polynomial in the form of PV=A o =A 1 P+A 2 +. . . A i P i . Thus, the digital computer produces a process variable representation as a modified digital output. Subsequently, the digital output from the computer is converted to a conventional 4-20 mA analog signal for use as a process control signal. The process variable transmitter apparatus utilizing the aforesaid method includes means for receiving an output from a process variable sensor, an analog-to-digital converter for converting the received output from the sensor to a digital representation, a digital computer, a non-volatile memory for storing an individualized correction equation determined during the manufacturing testing of the transmitter and a digital-to-analog converter for converting the computer output to an analog control signal.
Inventors
- 👤 John R. Malloy, deceased
- 👤 Arthur M. Olsen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 17:44
CPC Classifications
G; G08; G08C; G08C19/00; G08C19/02; G01; G01D; G01D18/00; G01D18/008; G01L; G01L27/00; G01L27/002
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
175 words
A method for digital calibration of a process variable sensor comprising the steps of storing a characterization equation in the form of PV=A 0 A 1 P+A 2 P 2 + . . . +A i P i where A i =f (S,T) and PV is the process variable, P is the output of a process variable differential value measuring sensor, S is the output of a process variable static value measuring sensor and T is the output of a sensor measuring an environmental temperature affecting the outputs of the process variable measuring sensors and where ##EQU2## measuring a process variable by the process variable sensor to produce an analog output signal representative of the process variable, converting the output from the process variable sensor to a digital representation thereof and supplying the digital representation to a digital computer to be used in computing a digital output in accordance with the stored characterization equation to produce a corrected version of the output of the process variable sensor independent of the effects of the environmental conditions.
Claim 2
Independent Claim
175 words
A method for digital calibration of a process variable sensor comprising the steps of storing a characterization equation in the form of PV=A 0 A 1 P+A 2 P 2 + . . . +A i P i where A i =f (S,T) and PV is the process variable, P is the output of a process variable differential value measuring sensor, S is the output of a process variable static value measuring sensor and T is the output of a sensor measuring an environmental temperature affecting the outputs of the process variable measuring sensors and where ##EQU2## measuring a process variable by the process variable sensor to produce an analog output signal representative of the process variable, converting the output from the process variable sensor to a digital representation thereof and supplying the digital representation to a digital computer to be used in computing a digital output in accordance with the stored characterization equation to produce a corrected version of the output of the process variable sensor independent of the effects of the environmental conditions.
Claim 3
Dependent Claim
27 words
A method as set forth in claim 1 which includes the further step of converting the digital output from the digital computer into an analog control signal.
Claim 4
Dependent Claim
18 words
A method as set forth in claim 2 wherein the analog control signal is a 4-20 mA signal.
Claim 5
Dependent Claim
13 words
A method as set forth in claim 1 wherein i≦5, n≦7 and m≦2.
Claim 6
Dependent Claim
10 words
A method as set forth in claim 1 wherein i≦5.
Claim 7
Dependent Claim
37 words
A method as set forth in claim 1 wherein the process variable is pressure (PP) and the environmental conditions are differential pressure (P) and static pressure (S) whereby PP=f (P,S,T) as the basis of the characterization equation.
Claim 8
Dependent Claim
160 words
A process variable transmitter apparatus comprising analog-to-digital converter means for converting an analog output from a process variable sensor into a digital representation thereof, a non-volatile memory means for storing a transmitter characterization equation in the form of PV=A 0 A 1 P+A 2 P 2 + . . . +A i P i where A i =f (S,T) and PV is the process variable, P is the output of a process variable differential value measuring sensor, S is the output of a process variable static value measuring sensor and T is the output of a sensor measuring an environmental temperature affecting the outputs of ther process variable measuring sensors and where ##EQU3## a digital computer means connected to said converter means and said memory means for computing a digital output in accordance with the stored transmitter characterization equation to produce a corrected version of the digital representation from said converter means independent of the effects of the environment conditions.
Claim 9
Dependent Claim
160 words
A process variable transmitter apparatus comprising analog-to-digital converter means for converting an analog output from a process variable sensor into a digital representation thereof, a non-volatile memory means for storing a transmitter characterization equation in the form of PV=A 0 A 1 P+A 2 P 2 + . . . +A i P i where A i =f (S,T) and PV is the process variable, P is the output of a process variable differential value measuring sensor, S is the output of a process variable static value measuring sensor and T is the output of a sensor measuring an environmental temperature affecting the outputs of ther process variable measuring sensors and where ##EQU3## a digital computer means connected to said converter means and said memory means for computing a digital output in accordance with the stored transmitter characterization equation to produce a corrected version of the digital representation from said converter means independent of the effects of the environment conditions.
Claim 10
Dependent Claim
29 words
A pressure transmitter as set forth in claim 7 and further including a digital-to-analog converter means for converting the digital output from said computer means into an analog signal.
Claim 11
Dependent Claim
18 words
A pressure transmitter as set forth in claim 8 wherein said analog signal is a 4-20 mA signal.
Claim 12
Dependent Claim
14 words
A pressure transmitter as set forth in claim 7 wherein i≦5, n≦7 and m≦2.
Claim 13
Dependent Claim
12 words
A process variable transmitter as set forth in claim 7 where i≦5.
Claim 14
Dependent Claim
37 words
A transmitter as set forth in claim 7 wherein the process variable is pressure (PP) and the environmental conditions are differential pressure (P) and static pressure (S) whereby PP=f (P,S,T) as the basis of the characterization equation.
Claim 15
Dependent Claim
10 words
A transmitter as set forth in claim 7 where i<5.
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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) | 1991-03-29 | 1991-09-28 | 1992-03-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-03-29 | 1995-09-28 | 1996-03-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-03-29 | 1999-09-28 | 2000-03-29 | $7700.00 | Window Closed / Lapsed |