Flow meter filter system and method

• US 20060265168A1
• Filed: 09/05/2003
• Published: 11/23/2006
• Est. Priority Date: 09/05/2003
• Status: Active Grant

• Current Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Original Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Inventors: McAnally, Craig B., Patten, Andrew Timothy, Hays, Paul J., Henrot, Denis M., Brinkman, Wayne R.
• Granted Patent: US 7,257,495 B2
• Time in Patent Office: Days
• US Class Current: 702/100
• CPC Class Codes: G01F 1/00 Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow measuring a proportion of the volume flow G01F5/00
• CPC Class Codes: G01F 1/8436 signal processing
• 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 15/06 Indicating or recording devices
• CPC Class Codes: G01F 25/00 Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume

Abstract

A flow meter filter system (200) according to an embodiment of the invention includes a noise pass filter (203) configured to receive a first version of a flow meter signal and filter out the flow meter data from the flow meter signal to leave a noise signal, a noise quantifier (204) configured to receive the noise signal from the noise pass filter (203) and measure noise characteristics of the noise signal, a damping adjuster (205) configured to receive the noise characteristics from the noise quantifier (204) and generate a damping value based on the noise characteristics, and a filter element (206) configured to receive a second version of the flow meter signal and receive the damping value from the damping adjuster (205), with the filter element (206) being further configured to damp the second version of the flow meter signal based on the damping value in order to produce a filtered flow meter signal.

Claims

1. A flow meter filter system (200) comprising:

a noise pass filter (203) configured to receive a first version of a flow meter signal and filter out the flow meter data from the flow meter signal to leave a noise signal;

a noise quantifier (204) configured to receive the noise signal from the noise pass filter (203) and measure noise characteristics of the noise signal;

a damping adjuster (205) configured to receive the noise characteristics from the noise quantifier (204) and generate a damping value based on the noise characteristics; and

a filter element (206) configured to receive a second version of the flow meter signal and receive the damping value from the damping adjuster (205), with the filter element (206) being further configured to damp the second version of the flow meter signal based on the damping value in order to produce a filtered flow meter signal.

2. The flow meter filter system (200) of claim 1, with the noise pass filter (203) comprising an Alternating Current (AC) coupling filter.

3. The flow meter filter system (200) of claim 1, with the noise pass filter (203) comprising a second-order Infinite Impulse Response (IIR) digital filter.

4. The flow meter filter system (200) of claim 1, wherein the noise characteristics include a maximum noise amplitude and a zero offset.

5. The flow meter filter system (200) of claim 1, wherein the damping adjuster (205) is further configured to receive an error signal generated by the filter element (206), with the error signal comprising a difference between the second version of the flow meter signal and the filtered flow meter signal.

6. The flow meter filter system (200) of claim 1, wherein the damping adjuster (205) is further configured to receive a predetermined maximum flow value.

7. The flow meter filter system (200) of claim 1, wherein the damping adjuster (205) is further configured to divide the zero offset by the predetermined maximum flow value in order to determine whether the noise signal is substantially centered around zero.

8. The flow meter filter system (200) of claim 1, wherein the damping adjuster (205) is further configured to input the noise characteristics into a damping table in order to generate the damping value.

9. The flow meter filter system (200) of claim 1, wherein the damping adjuster (205) is further configured to generate the damping value based on the noise characteristics and on a damping delay coefficient.

10. The flow meter filter system (200) of claim 1, with the filter element (206) comprising a second-order filter.

11. The flow meter filter system (200) of claim 1, with the filter element (206) comprising an Infinite Impulse Response (IIR) digital filter.

12. The flow meter filter system (200) of claim 1, with the filter element (206) comprising a second order Infinite Impulse Response (IIR) digital filter.

13. The flow meter filter system (200) of claim 1, wherein the noise signal has a frequency in the range of about 0.025 Hz to about 1.0 Hz.

14. The flow meter filter system (200) of claim 1, wherein the noise signal comprises cyclic noise.

15. The flow meter filter system (200) of claim 1, wherein the noise signal comprises cross-talk noise.

16. The flow meter filter system (200) of claim 1, wherein the flow meter signal comprises a Coriolis flow meter signal.

17. A method of removing noise from a flow meter signal, comprising the steps of:

receiving the flow meter signal;

applying a large damping value to the flow meter signal in order to produce a filtered flow meter signal if the flow meter signal is substantially quiescent; and

applying a small damping value to the flow meter signal in order to produce the filtered flow meter signal if the flow meter signal is experiencing a transition.

18. The method of claim 17, further comprising the steps of:

normalizing the flow meter signal from an original value to a normalized value prior to the damping; and

scaling the filtered flow meter signal of the damping step substantially back to the original flow meter signal magnitude.

19. The method of claim 17, further comprising the steps of:

filtering a noise signal substantially out of a first version of the flow meter signal;

measuring the noise signal to obtain noise characteristics; and

determining a damping value from the noise characteristics, with the damping value being selected to substantially remove the noise signal from the flow meter signal and produce the filtered flow meter signal.

20. The method of claim 17, further comprising the steps of:

filtering a noise signal substantially out of a first version of the flow meter signal;

measuring the noise signal to obtain noise characteristics;

determining a damping value from the noise characteristics, with the damping value being chosen to substantially remove the noise signal from the flow meter signal;

determining an error value between the second version of the flow meter signal and the filtered flow meter signal; and

feeding the error value back into the step of determining the damping value, wherein the error value is included in the damping value determination.

21. The method of claim 17, wherein the noise signal has a frequency in the range of about 0.025 Hz to about 1.0 Hz.

22. The method of claim 17, wherein the noise signal comprises cyclic noise.

23. The method of claim 17, wherein the noise signal comprises cross-talk noise.

24. The method of claim 17, wherein the flow meter signal comprises a Coriolis flow meter signal.

25. The method of claim 17, further comprising the steps of:

dividing a zero offset of the noise characteristics by the maximum flow value to obtain a noise value;

comparing the noise value to a predetermined quiescent threshold;

using the noise value for determining a new damping value if the noise value is less than the predetermined quiescent threshold; and

using a current damping value if the noise value is not less than the predetermined quiescent threshold.

26. A method of removing noise from a flow meter signal, comprising the steps of:

receiving the flow meter signal;

filtering a noise signal substantially out of a first version of the flow meter signal;

measuring the noise signal to obtain noise characteristics;

determining a damping value from the noise characteristics, with the damping value being selected to substantially remove the noise signal from the flow meter signal; and

damping the noise substantially out of a second version of the flow meter signal using the damping value in order to produce a filtered flow meter signal.

27. The method of claim 26, further comprising the steps of:

normalizing the flow meter signal from an original value to a normalized value prior to the damping; and

scaling the filtered flow meter signal of the damping step substantially back to the original flow meter signal magnitude.

28. The method of claim 26, further comprising the steps of:

determining an error value between the second version of the flow meter signal and the filtered flow meter signal; and

feeding the error value back into the step of determining the damping value, wherein the error value is included in the damping value determination.

29. The method of claim 26, with the damping further comprising the steps of:

applying a large damping value to the flow meter signal if the flow meter signal is substantially quiescent; and

applying a small damping value to the flow meter signal if the flow meter signal is experiencing a transition.

30. The method of claim 26, further comprising sampling the first version of the flow meter signal before the filtering.

31. The method of claim 26, wherein the noise characteristics include a noise amplitude and a zero offset.

32. The method of claim 26, wherein the noise signal has a frequency in the range of about 0.025 Hz to about 1.0 Hz.

33. The method of claim 26, wherein the noise signal comprises cyclic noise.

34. The method of claim 26, wherein the noise signal comprises cross-talk noise.

35. The method of claim 26, wherein the flow meter signal comprises a Coriolis flow meter signal.

36. The method of claim 26, further comprising the steps of:

dividing a zero offset of the noise characteristics by the maximum flow value to obtain a noise value;

comparing the noise value to a predetermined quiescent threshold;

using the noise value in the determining step for determining a new damping value if the noise value is less than the predetermined quiescent threshold; and

using a current damping value in the damping step if the noise value is not less than the predetermined quiescent threshold.