Temperature Prediction Transmitter

• US 20110224940A1
• Filed: 03/09/2010
• Published: 09/15/2011
• Est. Priority Date: 03/09/2010
• Status: Active Grant

• Current Assignee: Schneider Electric Systems USA, Inc. (Schneider Electric SE)
• Original Assignee: Invensys Systems Incorporated (Invensys PLC)
• Inventors: Howe, Spencer K.
• Granted Patent: US 8,301,408 B2
• Time in Patent Office: Days
• US Class Current: 702/130
• CPC Class Codes: G01D 3/032 affecting incoming signal, e.g. by averaging; gating undesired signals
• CPC Class Codes: G01K 1/00 Details of thermometers not specially adapted for particular types of thermometer circuits for reducing thermal inertia G01K7/42
• CPC Class Codes: G01K 7/42 Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature
• CPC Class Codes: G06F 17/00 Digital computing or data processing equipment or methods, specially adapted for specific functions information retrieval, database structures or file system structures therefor G06F16/00

Abstract

A system and method is provided for predicting a physical quality such as temperature, the measurement of which tends to be hindered by a time-related impediment. A single sensor is configured to detect, in real time, the physical quality Q_detect, and one or more infinite impulse response filters are configured with time constants correlated to the time-related impediment. The infinite impulse filter(a) are configured to filter Q_detect to output a filtered quality measurement (Q_filtered). A processor is configured to calculate, in real time, the estimated or predicted quality Q_estimate using Q_detect and Q_filtered.

Claims

1. A system for predicting a physical quality with an impediment to accurate measurement, comprising:

a sensor configured to detect, in real time, the physical quality (Q_detect), wherein measurement of the physical quality is subject to a time-related impediment;

a first infinite impulse response filter configured to filter Q_detect and to output a first filtered quality measurement (Q_filtered1); and

a processor configured to calculate, in real time, the estimated quality Q_estimate using Q_detect and Q_filtered1.

2. The system of claim 1, comprising:

a second infinite impulse response filter configured to filter Q_filtered1 and to output a second filtered quality measurement (Q_filtered2); and

wherein said processor is configured to calculate the estimated quality Q_estimate using Q_filtered1 and Q_ffitered2.

3. The system of claim 2, comprising:

an additional infinite impulse response filter configured to filter Q_filtered1 and to output an additional filtered quality measurement (Q_filteredadd); and

wherein said processor is configured to calculate the estimated quality Q_estimate using Q_filteredadd.

4. The system of claim 3, wherein said processor is configured to calculate the estimated quality Q_estimate using the formula Q_estimate=Q_detected1+(Q_detected1−

Q_filtered2)+(Q_detected1−

Q_filteredadd).

5. The system of claim 1, wherein the quality comprises temperature of a material and the impediment comprises a barrier disposed between the sensor and the material.

6. The system of claim 5, wherein the material comprises a process fluid and the barrier comprises a casing disposed about the temperature sensor, wherein the casing is configured for extension into process fluid flow.

7. The system of claim 6, comprising:

a second infinite impulse response filter configured to filter Q_filtered1 and to output a second filtered quality measurement (Q_filtered2); and

wherein said processor is configured to calculate the estimated quality Q_estimate using Q_filtered1 and Q_fitered2.

8. The system of claim 7, comprising no more than one temperature sensor.

9. The system of claim 7, comprising an additional infinite impulse response filter.

10. The system of claim 7, wherein said first infinite impulse response filter is configured to employ a first time constant (τ

₁) correlated to the time-related impediment.

11. The system of claim 10, wherein said second infinite impulse response filter is configured to employ a second time constant (τ

₂) correlated to the time-related impediment.

12. The system of claim 11, wherein τ

₂ is greater than or substantially equal to τ

₁.

13. The system of claim 2, wherein said processor is configured for calculation of Q_estimate by subtracting the value of Q_filtered2 from twice the value of Q_filtered1.

14. The system of claim 2, wherein said processor is configured for calculation of Q_estimate by calculating the difference between Q_filtered1 and Q_filtered2, and adding the difference to Q_filtered1.

15. The system of claim 1, wherein said processor is configured for recording of a plurality of data points of Q_detected over time.

16. The system of claim 15, wherein said processor is configured for determining the slope of Q_detected at the plurality of data points.

17. The system of claim 16, wherein said processor is configured for determining Q_estimate using the slope of Q_detected at said plurality of data points.

18. The system of claim 17, wherein said processor is configured for determining a final value for Q_estimate, denoted as Q_{estimatefinal}, by the formula Q_{estimatefinal}=(SlopeQ_detected×

K)+(Q_estimate), wherein K is a constant having a value correlated to the time-related impediment.

19. A method for transforming physical quality data into an estimated measured quality, comprising:

a) obtaining, with a sensor in real time, data representing a physical quality (Q_detect), wherein an impediment exists to the detection of the physical quality;

b) filtering Q_detect through a first IIR filter (IIR₁), wherein the IIR₁ outputs Q_filtered1;

c) calculating, with a processor in real time, the estimated measured quality (Q_estimate) using Q_filtered1 and Q_detect.

20. The method of claim 19, wherein said obtaining (a) comprises obtaining, with a temperature sensor, data representing a physical quality (Q_detect) in the form of temperature, wherein the impediment comprises a barrier disposed between the temperature sensor and the material;

and said filtering (b) and calculating (c) is effected by a temperature compensation transmitter.

21. The method of claim 20, wherein the material comprises a process fluid and the barrier comprises a casing disposed about the temperature sensor, wherein the casing is configured for extension into process fluid flow.

22. The method of claim 21, further comprising:

;

e) disposing the temperature sensor within the casing; and

inserting the casing into the process fluid flow.

23. The method of claim 19, comprising:

d) filtering Q_filtered1 through another infinite impulse response filter configured to output another filtered quality measurement (Q_filtered2); and

wherein said calculating (c) includes calculating the estimated quality Q_estimate using Q_filtered1 and Q_fitered2.

24. The method of claim 23, wherein said calculating (c) comprises calculating, with the processor, Q_estimate by subtracting the value of Q_filtered2 from twice the value of Q_filtered1.

25. The method of claim 23, wherein said calculating (c) comprises calculating, with the processor, Q_estimate by calculating the difference between Q_filtered1 and Q_filtered2, and adding the difference to Q_filtered1.

26. The method of claim 23, comprising configuring the infinite impulse response filter to employ a first time constant (τ

₁) correlated to the time-related impediment.

27. The method of claim 26, comprising configuring the other infinite impulse response filter to employ a second time constant (τ

₂) correlated to the time-related impediment.

28. The method of claim 23, comprising:

filtering Q_filtered1 through an additional infinite impulse response filter configured to output an additional filtered quality measurement (Q_filteredadd); and

wherein said calculating (c) includes calculating the estimated quality Q_estimate using Q_filtered1, Q_filtered2 and Q_filteredadd.

29. The system of claim 28, wherein said processor is configured to calculate the estimated quality Q_estimate the formula Q_estimate=Q_filtered1+(Q_filtered1−

Q_filtered2)+(Q_filtered1−

Q_filteredadd).

30. The method of claim 19, comprising recording, with the processor, a plurality of data points of Q_detected over time.

31. The method of claim 30, comprising determining, with the processor, in real time, the slope of Q_detected at the plurality of data points.

32. The method of claim 31, wherein said calculating (c) comprises determining Q_estimate using the slope of Q_detected at the plurality of data points.

33. The method of claim 32, wherein said calculating (c) comprises calculating with the processor in real time, a final value for Q_estimate, denoted as Q_{estimatefinal}, by the formula Q_{estimatefinal}=(SlopeQ_detected×

K)+(Q_estimate), wherein K is a constant having a value correlated to the time-related impediment.