Field device with measurement accuracy reporting

• US 20100274528A1
• Filed: 04/22/2009
• Published: 10/28/2010
• Est. Priority Date: 04/22/2009
• Status: Abandoned Application

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Kent, David J., Lecuyer, Gregory Jacques, Wehrs, David L.
• Application Number:
  US12/386,760
• Publication Number:
  US 20100274528A1
• Time in Patent Office: Days
• US Class Current: 702/183
• CPC Class Codes: G05B 19/0428 Safety, monitoring G05B19/0423 takes precedence
• CPC Class Codes: G05B 2219/25428 Field device
• CPC Class Codes: G05B 2219/37008 Calibration of measuring system, probe, sensor
• 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

A field device includes a sensor for sensing a process parameter, a processor for producing a measurement value as a function of the sensed process parameter, and a communication interface for transmitting an output based upon the measurement value. The processor also calculates a measurement precision value associated with the measurement value.

Claims

1. A field device comprising:

a sensor for sensing a process parameter;

a processor for producing a measurement value as a function of the process parameter sensed, and calculating a measurement precision value for the measurement value based upon operating conditions of the field device; and

a communication interface for transmitting a field device measurement output based upon the measurement value and a diagnostic output based upon the measurement precision value.

2. The field device of claim 1, wherein the diagnostic output is a function of a comparison of the measurement precision value and a stored required performance limit.

3. The field device of claim 1, wherein the diagnostic output provides an indication of a need for calibration of the field device.

4. The field device of claim 3, wherein the processor identifies the occurrence of an out-of-range process parameter sensed by the sensor and causes the diagnostic output to provide an indication of a need for calibration of the field device.

5. The field device of claim 4, wherein the out-of-range process parameter is an overpressure.

6. The field device of claim 1, wherein the diagnostic output provides an indication of time until calibration of the field device is needed.

7. The field device of claim 1 and further comprising:

a local display for displaying information based upon the measurement precision value.

8. The field device of claim 7, wherein the local display displays information including at least one of total probable error of the field device, total probable error of a primary element associated with the field device, a stability error, and a total calculated error.

9. The field device of claim 7, wherein the local display displays a countdown to a next calibration of the field device.

10. The field device of claim 7, wherein the processor identifies the occurrence of an out-of-range process parameter sensed by the sensor and causes the local display to display an indication of the need for calibration of the field device.

11. The field device of claim 10, wherein the out-of-range process parameter is an overpressure.

12. The field device of claim 1, wherein the measurement precision value comprises a total probable error of the field device.

13. The field device of claim 12, wherein the total probable error is calculated by the processor based upon a stored reference accuracy of the sensor and a temperature effect related to temperature of the field device.

14. The field device of claim 13, wherein the process parameter is pressure and the total probable error is calculated by the processor based upon the stored reference accuracy, the temperature effect, and a static effect related to static line pressure.

15. The field device of claim 12, wherein the measurement precision value further comprises a total probable error of a primary element associated with the field device.

16. The field device of claim 15, wherein the total probable error of the primary element is calculated by the processor based upon a stored reference accuracy of the sensor and a temperature effect related to temperature of the field device.

17. The field device of claim 16, wherein the process parameter is pressure and the total probable error of the primary element is calculated by the processor based upon the stored reference accuracy, the temperature effect, and a static effect related to static line pressure.

18. The field device of claim 12, wherein the measurement precision value further comprises a stability error.

19. The field device of claim 18 and further comprising:

a time reference for providing an operating time reference for use by the processor in calculating the stability error.

20. The field device of claim 1, wherein the diagnostic output is transmitted as a secondary variable with each transmission of the measurement value.

21. A method of measuring process parameters, the method comprising:

sensing a process parameter;

producing a measurement value representative of the process parameter sensed;

providing a measurement output based upon the measurement value;

calculating a measurement precision value based upon stored coefficients and data related to operating conditions of the field device; and

providing a measurement precision diagnostic output based upon the measurement precision value.

22. The method of claim 21, wherein the measurement precision value includes a total probable error.

23. The method of claim 22, wherein the total probable error is a function of a reference accuracy and a temperature effect.

24. The method of claim 23, wherein the total probable error is also a function of a static effect.

25. The method of claim 22, wherein the measurement precision value includes a stability error.

26. The method of claim 21, wherein the providing measurement precision diagnostic output comprises:

comparing the measurement precision value to a required performance limit; and

producing the measurement precision diagnostic output as a function of the comparison.

27. The method of claim 21 and further comprising:

sensing occurrence of any out-of-range condition that affects calibration; and

causing the measurement precision diagnostic output to indicate a need for calibration when an out-of-range condition is sensed.

28. The method of claim 27, wherein the measurement value is a pressure value, and the out-of-range condition is an overpressure condition.

29. The method of claim 21, wherein the measurement precision diagnostic output comprises a secondary variable communicated with the measurement output.