Process device with sampling skew

• US 8,340,791 B2
• Filed: 10/01/2009
• Issued: 12/25/2012
• Est. Priority Date: 10/01/2009
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Schulte, John P.
• Primary Examiner(s): Hartman, Jr., Ronald
• Application Number:
  US12/571,622
• Publication Number:
  US 20110082568A1
• Time in Patent Office: 1,181 Days
• Field of Search: 324/76.11, 324/76.52, 324/76.59, 700/71, 700/72, 700/73, 738/614.2, 738/616.6, 702/79, 702/89, 702/187, 702/189
• US Class Current: 700/71
• CPC Class Codes: G01F 15/00 Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
• CPC Class Codes: G01F 15/063 using electrical means
• CPC Class Codes: G01F 23/802 Particular electronic circuits for digital processing equipment
• CPC Class Codes: G01F 23/804 containing circuits handling parameters other than liquid level
• CPC Class Codes: G05B 23/0221 Preprocessing measurements, e.g. data collection rate adjustment; Standardization of measurements; Time series or signal analysis, e.g. frequency analysis or wavelets; Trustworthiness of measurements; Indexes therefor; Measurements using easily measured parameters to estimate parameters difficult to measure; Virtual sensor creation; De-noising; Sensor fusion; Unconventional preprocessing inherently present in specific fault detection methods like PCA-based methods

Abstract

An industrial process device for monitoring or controlling an industrial process includes a first input configured to receive a first plurality of samples related to a first process variable and a second input configured to receive a second plurality of samples related to a second process variable. Compensation circuitry is configured to compensate for a time difference between the first plurality of samples and the second plurality of samples and provide a compensated output related to at least one of the first and second process variables. The compensated output can comprise, or can be used to calculate a third process variable. The third process variable can be used to monitor or control the industrial process.

Claims

1. An industrial process apparatus for monitoring or controlling an industrial process, comprising:

a first process variable sensor configured to sense a first process variable and provide a first process variable sensor output;

a second process variable sensor configured to sense a second process variable and provide a second process variable sensor output;

a first analog to digital converter configured to sample the first process variable sensor output at a first sample rate and provide a first plurality of samples;

a second analog to digital converter configured to sample the second process variable sensor output at a second sample rate and provide a second plurality of samples, wherein the first and second sample rates are asynchronous;

a first input configured to receive the first plurality of samples related to the first process variable;

a second input configured to receive the second plurality of samples related to the second process variable; and

compensation circuitry configured to compensate for a time difference between the first plurality of samples and the second plurality of samples due to the first and second sampling rates being asynchronous and provide a compensated output related to both process variables.

2. The apparatus of claim 1 wherein the compensated output is based upon an extrapolation of the first plurality of samples related to the first process variable.

3. The apparatus of claim 2 wherein the compensation circuitry is further configured to provide a compensated output related to the second process variable.

4. The apparatus of claim 1 wherein the compensated output is based upon an interpolation of the first plurality of samples related to the first process variable.

5. The apparatus of claim 4 wherein the interpolation is based upon two adjacent samples of the first plurality of samples related to the first process variable.

6. The apparatus of claim 1 wherein the compensated output is based upon a curve fit between at least three samples in the first plurality of samples related to the first process variable.

7. The apparatus of claim 6 wherein the curve fit comprises a polynomial curve fit.

8. The apparatus of claim 1 wherein the first and second plurality of samples are time stamped.

9. The apparatus of claim 1 including measurement configured to calculate a third process variable as a function of a compensated first plurality of samples related to the first process variable and the second plurality of samples related to the second process variable.

10. The apparatus of claim 1 wherein the compensation circuitry provides damping to the first and second plurality samples.

11. The apparatus of claim 10 wherein the compensation circuitry comprises a low pass filter.

12. The apparatus of claim 1 wherein at least one of the first and second inputs comprises a wireless input.

13. The apparatus of claim 1 including measurement circuitry configured to calculate a differential pressure based upon a compensated value of the first process variable and the second process variable.

14. A method for use in an industrial process device for compensating for time difference between two process variables comprising:

receiving a first plurality of samples related to a first process variable sampled at a first sample rate;

receiving a second plurality of samples related to a second process variable sampled at a second sample rate, wherein the first and second sample rates are asynchronous and there is a time differential between the samples of the first and second process variables;

compensating for the time difference between the first plurality of samples and the second plurality of samples due to the first and second sampling rates being asynchronous;

providing an output related to a third process variable as a function of a compensated value of first process variable and the second process variable.

15. The method of claim 14 wherein the compensating is based upon an extrapolation of the first plurality of samples related to the first process variable.

16. The method of claim 14 wherein the compensating is based upon interpolating between at least two of the first plurality of samples related to the first process variable.

17. The method of claim 16 wherein the interpolating is based upon two adjacent samples of the first plurality of samples related to the first process variable.

18. The method of claim 14 wherein the compensating is based upon a curve fit between at least three samples in the first plurality of samples related to the first process variable.

19. The method of claim 18 wherein the curve fit comprises a polynomial curve fit.

20. The method of claim 14 wherein the first and second plurality of samples are time stamped.

21. The method of claim 14 including calculating a third process variable as a function of a compensated first plurality of samples related to the first process variable and the second plurality of samples related to the second process variable.

22. The method of claim 14 wherein the compensating comprises damping the first and second plurality of samples.

23. The method of claim 22 wherein the damping comprises a low pass filtering.

24. The method of claim 14 wherein at least one of the first and second plurality of samples is received from a wireless input.

25. The method of claim 14 including calculating a differential pressure based upon a compensated value of the first process variable and the second process variable.

26. The method of claim 14 including compensating the second process variable.