Phase measurement in measuring device

• US 20050021259A1
• Filed: 05/28/2004
• Published: 01/27/2005
• Est. Priority Date: 05/30/2003
• Status: Active Grant

• Current Assignee: ABB Limited
• Original Assignee: ABB Limited
• Inventors: Wray, Troy
• Granted Patent: US 7,110,899 B2
• Time in Patent Office: Days
• 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 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; 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 measurement device.

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

10. A method according to claim 9, comprising calibrating the device so as to estimate the phase N_L.

11. A method according to claim 1, wherein the measurement device is a flow meter.

12. A method according to claim 6 wherein the measurement device is a flow meter and wherein the further signal is an AC excitation signal used for operating the flow meter.

13. 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 measurement device 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.

14. 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.

15. A measurement device according to claim 14, further comprising means for determining the amplitude of the signal from the result of the correlation.

16. A measurement device according to claim 14, wherein the correlating means is arranged to correlate the digitised signal or a signal derived therefrom with a numerically generated sinusoidal reference signal.

17. A measurement device according to claims 14, 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.

18. A measurement device according to claim 14, 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.

19. A measurement device according to claim 14, 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 measurement device.

22. A measurement device according to claim 14, further comprising means for providing an estimate N_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 measurement device, and a phase corresponding to the estimated phase N_L.

23. A measurement device according to claim 22, wherein the means for providing an estimate N_L comprises means for calibrating the device.

24. A measurement device according to claim 14, being a flow meter.

25. A measurement device according to claim 18, wherein the measurement device comprises a flow meter and wherein the further signal is an AC excitation signal to be used for operating the flow meter.

26. A measurement device according to claim 24, wherein the flow meter is a Coriolis meter.

27. A measurement device according to claim 24, wherein the flow meter is an electromagnetic flow meter.

20. A measurement device 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.

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

28. A computer readable medium for storing a computer program suitable for determining the phase of a signal in a measurement device 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.

29. A computer readable medium for storing a computer program suitable for processing a signal in a measurement device 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.