Phase measurement in measuring device

• US 7,110,899 B2
• Filed: 05/28/2004
• Issued: 09/19/2006
• Est. Priority Date: 05/30/2003
• Status: Expired due to Fees

• Current Assignee: ABB Limited
• Original Assignee: ABB Limited
• Inventors: Wray, Troy
• Primary Examiner(s): Assouad, Patrick J.
• Application Number:
  US10/856,009
• Publication Number:
  US 20050021259A1
• Time in Patent Office: 844 Days
• Field of Search: None
• US Class Current: 702/72
• CPC Class Codes: G01F 1/60 Circuits therefor
• CPC Class Codes: G01F 1/8431 electronic circuits
• CPC Class Codes: G01F 1/8436 signal processing
• CPC Class Codes: G01F 1/849 having straight measuring conduits

Abstract

Methods and apparatus for determining the phase of a signal in a measurement device having a digital signal processor are described. The signal is digitised and the digitised signal, or a signal derived therefrom, is numerically correlated with a numerically generated reference signal. In one embodiment, the reference signal has a predetermined phase. In a further embodiment, the numerically generated reference signal has a reference phase and the phase is determined from the result of the correlation. The techniques described herein may reduce the amount of information lost in determining the signal phase.

Claims

1. A method of determining the phase of a signal in a coriolis flowmeter having a digital signal processor, comprising

digitising the signal;

numerically correlating the digitised signal or a signal derived therefrom with a numerically generated reference signal having a reference phase; and

determining the phase from the result of the correlation.

2. A method according to claim 1, further comprising determining the amplitude of the signal from the result of the correlation.

3. A method according to claim 1, wherein the numerically generated reference signal comprises a sinusoidal signal.

4. A method according to claim 1, wherein numerically correlating the digitised signal or a signal derived therefrom comprises numerically correlating the digitised signal or a signal derived therefrom with numerically generated first and second reference signals having a quadrature phase relation.

5. A method according to claim 1, wherein the reference signal or, in the case of two or more reference signals at least one of them, has a predetermined phase.

6. A method according to claim 1, wherein the reference signal or, in the case of two or more reference signals at least one of them, has the same frequency and phase as a further signal used for operating the coriolis flowmeter.

9. A method according to claim 1, further comprising providing an estimate φ

_L of the phase of the digitised signal, wherein the reference signal or, in the case of two or more reference signals at least one of them, has the same frequency as a further signal used for operating the coriolis flowmeter, and a phase corresponding to the estimated phase φ

_L.

10. A method according to claim 9, comprising calibrating the coriolis flowmeter so as to estimate the phase φ

_L.

11. A method according to claim 6 wherein the coriolis flowmeter is a flow meter and wherein the further signal is an AC excitation signal used for operating the coriolis flow meter.

12. A method according to claim 10, further comprising determining a measure of flow rate based on said phase.

7. A method of processing a signal in a coriolis flowmeter having a digital signal processor comprising

digitising the signal;

and

numerically correlating the digitised signal or a signal derived therefrom with a numerically generated reference signal, wherein the reference signal has a predetermined phase.

8. A method according to claim 7, further comprising determining the amplitude from the result of the correlation and determining a measure of flow rate based on said amplitude.

13. A coriolis flowmeter comprising

means for digitising a signal;

means for numerically correlating the digitised signal or a signal derived therefrom with a numerically generated reference signal; and

means for determining the phase of the signal from the result of the correlation.

14. A coriolis flowmeter according to claim 13, further comprising means for determining the amplitude of the signal from the result of the correlation.

15. A coriolis flowmeter according to claim 13, wherein the correlating means is arranged to correlate the digitised signal or a signal derived therefrom with a numerically generated sinusoidal reference signal.

16. A coriolis flowmeter according to claim 13, wherein the correlating means is arranged to correlate the digitised signal or a signal derived therefrom with numerically generated first and second reference signals having a quadrature phase relation.

17. A coriolis flowmeter according to claim 13, wherein the correlating means is arranged to correlate the digitised signal or a signal derived therefrom with a numerically generated reference signal having a predetermined phase.

18. A coriolis flowmeter according to claim 13, wherein the correlating means is arranged to correlate the digitised signal or a signal derived therefrom with a numerically generated reference signal having the same frequency and phase as a further signal to be used for operating the coriolis flowmeter.

21. A coriolis flowmeter according to claim 13, further comprising means for providing an estimate φ

_L of the phase of the digitised signal, wherein the correlating means is arranged to correlate the digitised signal or a signal derived therefrom with a numerically generated reference signal having the same frequency as a further signal used for operating the coriolis flowmeter, and a phase corresponding to the estimated phase φ

_L.

22. A coriolis flowmeter according to claim 21, wherein the means for providing an estimate φ

_L comprises means for calibrating the coriolis flowmeter.

23. A coriolis flowmeter according to claim 17, wherein the further signal is an AC excitation signal to be used for operating the coriolis flow meter.

19. A coriolis flowmeter comprising

means for digitising a signal;

and

means for numerically correlating the digitised signal or a signal derived therefrom with a numerically generated reference signal having a predetermined phase.

20. A coriolis flowmeter according to claim 19, further comprising means for determining the amplitude of the signal from the result of the correlation, wherein the coriolis flowmeter comprises a flow meter and further comprises means for determining a measure of flow rate based on said amplitude.

24. A computer readable medium for storing a computer program suitable for determining the phase of a signal in a coriolis flowmeter having a digital signal processor, comprising

computer code for digitising the signal;

computer code for numerically correlating the digitised signal or a signal derived therefrom with a numerically generated reference signal; and

computer code for determining the phase from the result of the correlation.

25. A computer readable medium for storing a computer program suitable for processing a signal in a coriolis flowmeter having a digital signal processor, comprising

computer code for digitising the signal;

and

computer code for numerically correlating the digitised signal or a signal derived therefrom with a numerically generated reference signal having a predetermined phase.

26. A method of determining the phase of a signal in a measurement device having a digital signal processor, comprising

digitising the signal;

numerically correlating the digitised signal or a signal derived therefrom with a numerically generated reference signal having a reference phase;

determining the phase from the result of the correlation;

providing an estimate φ

_L of the phase of the digitised signal, wherein the reference signal or, in the case of two or more reference signals at least one of them, has the same frequency as a further signal used for operating the measurement device, and a phase corresponding to the estimated phase φ

_L;

calibrating the device so as to estimate the phase φ

_L; and

determining a measure of flow rate based on said phase.

27. A measurement device comprising

means for digitising a signal;

means for numerically correlating the digitised signal or a signal derived therefrom with a numerically generated reference signal; and

means for determining the phase of the signal from the result of the correlation;

means for providing an estimate φ

_L of the phase of the digitised signal, wherein the correlating means is arranged to correlate the digitised signal or a signal derived therefrom with a numerically generated reference signal having the same frequency as a further signal used for operating the coriolis flowmeter, and a phase corresponding to the estimated phase φ

_L.

28. A measurement device according to claim 27, wherein the means for providing an estimate φ

_L comprises means for calibrating the coriolis flowmeter.