Mass flow meter or controller with inclination sensor

• US 7,409,871 B2
• Filed: 03/16/2006
• Issued: 08/12/2008
• Est. Priority Date: 03/16/2006
• Status: Active Grant

• Current Assignee: Brooks Instrument LLC (Illinois Tool Works Inc.)
• Original Assignee: Celerity Incorporated (ICHOR Holdings, Ltd.)
• Inventors: Wang, Chiun, Redemann, Eric J
• Primary Examiner(s): BARNES-BULLOCK, CRYSTAL JOY
• Application Number:
  US11/377,911
• Publication Number:
  US 20070219650A1
• Time in Patent Office: 880 Days
• Field of Search: 73/11.6, 73/15.7, 73/530.4, 731/521.8, 731/522.9, 732/025, 738/20, 738/610.1, 738/610.2, 738/613.51, 738/613.4, 738/617.3, 702/45, 702/50, 702/55, 702/100, 700/282
• US Class Current: 73/861.01
• CPC Class Codes: G01F 1/6847 where sensing or heating elements are not disturbing the fluid flow, e.g. elements mounted outside the flow duct
• 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 5/00 Measuring a proportion of the volume flow
• CPC Class Codes: G05D 7/0635 by action on throttling means G05D7/0688, G05D7/0694 take precedence

Abstract

A thermal mass flow meter associated with an inclination sensor that detects an angle of inclination of at least one portion of a thermal mass flow sensor relative to at least one reference axis. Based upon the detected angle of inclination, the output signal of the mass flow meter that is indicative of the mass flow rate of fluid through the sensor may be compensated to account for any inaccuracies relating to the orientation in which the mass flow meter is installed. Inaccuracies for which compensation may be provided include thermal siphoning effects and fluid buoyancy effects. By compensating for such inaccuracies, the mass flow meter may be used in any orientation, and/or may be used in non-inertial (e.g., accelerating) environments. The flow meter may be used as a stand alone device, or incorporated in a thermal mass flow controller.

Claims

1. A mass flow meter having a fluid inlet and a fluid outlet, comprising:

a thermal mass flow sensor to provide a first electrical signal indicative of a mass flow rate of a fluid flowing between the fluid inlet and the fluid outlet, the thermal mass flow sensor having a sensor inlet portion fluidly connected to the fluid inlet, a sensor outlet portion fluidly connected to the fluid outlet, and a sensor measuring portion disposed between and fluidly connected to the sensor inlet portion and the sensor outlet portion;

at least one inclination sensor to provide at least one second electrical signal indicative of an angle of inclination of at least one of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to at least one reference axis; and

a controller, to receive the first electrical signal and the at least one second electrical signal, calculate a correction factor based upon the at least one second electrical signal, and apply the correction factor to the first electrical signal to provide a third electrical signal indicative of the mass flow rate of the fluid flowing between the fluid inlet and the fluid outlet that is compensated for the angle of inclination of the at least one of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to the at least one reference axis.

2. The mass flow meter of claim 1, wherein the third electrical signal is compensated for differences in a density of the fluid in the sensor inlet portion and a density of the fluid in the sensor outlet portion.

3. The mass flow meter of claim 2, wherein an amount of compensation in the third electrical signal for the differences in the density of the fluid in the sensor inlet portion and the density of fluid in the sensor outlet portion is proportional to a difference in the density of the fluid in the sensor inlet portion and the density of the fluid in the sensor outlet portion, multiplied by a force of a gravitational field in an orientation in which the thermal mass flow sensor is to be operated and an effective height of the sensor inlet portion and the sensor outlet portion in a direction of the gravitational field in the orientation in which the thermal mass flow sensor is to be operated.

4. The mass flow meter of claim 2, wherein the thermal mass flow sensor is enclosed within a sensor housing, and wherein the third electrical signal is further compensated for convective effects between the sensor housing and its surrounding environment.

5. The mass flow meter of claim 2, wherein the thermal mass flow sensor is enclosed within a sensor housing, the sensor housing is enclosed within a second outer housing, and wherein the third electrical signal is further compensated for convective effects between the sensor housing and the second outer housing.

6. The mass flow meter of claim 1, wherein the thermal mass flow sensor is enclosed within a sensor housing, and wherein the third electrical signal is compensated for convective effects between the sensor housing and its surrounding environment.

7. The mass flow meter of claim 6, wherein an amount of compensation in the third electrical signal for the convective effects between the sensor housing and its surrounding environment is proportional to a fixed constant multiplied by the angle of inclination of the at least one of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to the at least one reference axis, and wherein the fixed constant is determined during calibration of the mass flow meter under vacuum conditions.

8. The mass flow meter of claim 1, wherein the thermal mass flow sensor is enclosed within a sensor housing, the sensor housing is enclosed within a second outer housing, and wherein the third electrical signal is further compensated for convective effects between the sensor housing and the second outer housing.

9. The mass flow meter of claim 1, further comprising:

an adjacent fluid flow path having a flow path inlet disposed proximate to the sensor inlet portion and fluidly connected to the fluid inlet, and a flow path outlet disposed proximate to the sensor outlet portion and fluidly connected to the fluid outlet.

10. The mass flow meter of claim 9, further comprising:

a bypass disposed in the adjacent fluid flow path.

11. The mass flow meter of claim 9, wherein the third electrical signal is compensated for recirculation of fluid between the thermal mass flow sensor and the adjacent fluid flow path.

12. The mass flow meter of claim 11, wherein the third electrical signal is further compensated for differences in a density of the fluid in the sensor inlet portion and a density of the fluid in the sensor outlet portion.

13. The mass flow meter of claim 12, wherein the thermal mass flow sensor is enclosed within a sensor housing, the sensor housing is enclosed within a second outer housing, and wherein the third electrical signal is further compensated for convective effects between the sensor housing and the second outer housing.

14. The mass flow meter of claim 11, wherein the thermal mass flow sensor is enclosed within a sensor housing, the sensor housing is enclosed within a second outer housing, and wherein the third electrical signal is further compensated for convective effects between the sensor housing and the second outer housing.

15. The mass flow meter of claim 9, wherein the at least one second electrical signal is indicative of an angle of inclination of the sensor measuring portion relative to the at least one reference axis, and wherein the third electrical signal is compensated for recirculation of fluid between the thermal mass flow sensor and the adjacent fluid flow path.

16. The mass flow meter of claim 15, wherein an amount of compensation in the third electrical signal for the recirculation of the fluid between the thermal mass flow sensor and the adjacent fluid flow path is proportional to a difference in density between the fluid in the sensor measuring portion and the fluid in the adjacent fluid flow path, multiplied by a function of the angle of inclination of the sensor measuring portion relative to the at least one reference axis.

17. The mass flow meter of claim 15, wherein an amount of compensation in the third electrical signal for the recirculation of the fluid between the thermal mass flow sensor and the adjacent fluid flow path is proportional to a difference in density between the fluid in the sensor measuring portion and the fluid in the adjacent fluid flow path, multiplied by a function of the angle of inclination of the sensor measuring portion relative to the at least one reference axis, and divided by a mean viscosity of the fluid in the sensor measuring portion.

18. The mass flow meter of claim 9, wherein the at least one second electrical signal is indicative of an angle of inclination of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to three orthogonal reference axes, and wherein the third electrical signal is compensated for recirculation of fluid between the thermal mass flow sensor and the adjacent fluid flow path and for differences in a density of the fluid in the sensor inlet portion and a density of the fluid in the sensor outlet portion.

19. The mass flow meter of claim 18, wherein an amount of compensation in the third electrical signal for the differences in the density of the fluid in the sensor inlet portion and the density of fluid in the sensor outlet portion is proportional to a difference in the density of the fluid in the sensor inlet portion and the density of the fluid in the sensor outlet portion, multiplied by a force of a gravitational field in an orientation in which the thermal mass flow sensor is to be operated and an effective height of the sensor inlet portion and the sensor outlet portion in a direction of the gravitational field in the orientation in which the thermal mass flow sensor is to be operated.

20. The mass flow meter of claim 19, wherein an amount of compensation in the third electrical signal for the recirculation of the fluid between the thermal mass flow sensor and the adjacent fluid flow path is proportional to a difference in density between the fluid in the sensor measuring portion and the fluid in the adjacent fluid flow path, multiplied by a function of the angle of inclination of the sensor measuring portion relative to the three orthogonal reference axes, and divided by a mean viscosity of the fluid in the sensor measuring portion.

21. The mass flow meter of claim 20, wherein the thermal mass flow sensor is enclosed within a sensor housing, the sensor housing is enclosed within a second outer housing, and wherein the third electrical signal is further compensated for convective effects between the sensor housing and the second outer housing.

22. The mass flow meter of claim 21, wherein an amount of compensation in the third electrical signal for convective effects between the sensor housing and the second outer housing is proportional to a fixed constant multiplied by the angle of inclination of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to the three orthogonal reference axes, and wherein the fixed constant is determined during calibration of the mass flow meter under vacuum conditions.

23. The mass flow meter of claim 18, wherein the thermal mass flow sensor is enclosed within a sensor housing, the sensor housing is enclosed within a second outer housing, and wherein the third electrical signal is further compensated for convective effects between the sensor housing and the second outer housing.

24. The mass flow meter of claim 23, further comprising:

at least one temperature sensor, operatively coupled to the controller, to measure a temperature of the fluid in at least one location disposed between the fluid inlet and the fluid outlet;

wherein a value of the density of the fluid in the sensor inlet portion and the sensor outlet portion is adjusted based upon the measured temperature.

25. The mass flow meter of claim 24, further comprising:

at least one pressure sensor, operatively coupled to the controller, to measure a pressure of the fluid in at least one location disposed between the fluid inlet and the fluid outlet;

wherein the density of the fluid in the sensor inlet portion and the sensor outlet portion is further adjusted based upon the measured pressure.

26. The mass flow meter of claim 23, wherein the mass flow meter is included within a mass flow controller, the mass flow controller including a controlled valve.

27. The mass flow meter of claim 23, wherein an amount of compensation for at least one of the recirculation of fluid between the thermal mass flow sensor and the adjacent fluid flow path, the differences in the density of the fluid in the sensor inlet portion and the density of the fluid in the sensor outlet portion, and the convective effects between the sensor housing and the second outer housing, is adjusted based upon the mass flow rate of the fluid flowing between the fluid inlet and the fluid outlet.

28. A method of determining a mass flow rate of a fluid flowing in a fluid flow path that includes a sensor flow path having a sensor inlet portion, a sensor outlet portion, and a sensor measuring portion, the method comprising acts of:

determining a flow rate of the fluid flowing in the sensor measuring portion of the sensor flow path;

determining an angle of inclination of at least one of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to at least one reference axis;

calculating at least one correction factor based upon the determined angle of inclination of the at least one of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to at least one reference axis; and

determining the mass flow rate of the fluid flowing in the fluid flow path based upon the determined flow rate of the fluid flowing in the sensor measuring portion of the sensor flow path and the at least one calculated correction factor.

29. The method of claim 28, wherein the act of calculating includes an act of calculating a first correction factor that accounts for differences in a density of the fluid in the sensor inlet portion and a density of the fluid in the sensor outlet portion, and the determined angle of inclination of at least one of the sensor inlet portion and the sensor outlet portion relative to the at least one reference axis.

30. The method of claim 29, wherein the first correction factor is proportional to a difference in the density of the fluid in the sensor inlet portion and the density of the fluid in the sensor outlet portion, multiplied by a force of a gravitational field in an orientation in which the sensor flow path is to be operated and an effective height of the sensor inlet portion and the sensor outlet portion in a direction of the gravitational field in the orientation in which the sensor flow path is to be operated.

31. The method of claim 28, wherein the sensor flow path is enclosed within a sensor flow path housing, and wherein the act of calculating includes an act of calculating a first correction factor that accounts for convective effects between the sensor flow path housing and its surrounding environment, and the determined angle of inclination of the at least one of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to the at least one reference axis.

32. The method of claim 31, wherein the first correction factor is proportional to a fixed constant multiplied by a function of the angle of inclination of the at least one of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to the at least one reference axis, and wherein the fixed constant is determined during calibration of the sensor flow path under vacuum conditions.

33. The method of claim 28, wherein the fluid flow path further includes a first fluid flow path and the sensor flow path, the sensor flow path being fluidly connected to the first fluid flow path, wherein the act of calculating includes an act of calculating a first correction factor that accounts for recirculation of fluid between the first fluid flow path and the sensor flow path and the determined angle of inclination of the sensor measuring portion relative to the at least one reference axis.

34. The method of claim 33, wherein the first correction factor is proportional to a difference in density between the fluid in the sensor measuring portion and the fluid in the first fluid flow path, multiplied by a function of the angle of inclination of the sensor measuring portion relative to the at least one reference axis.

35. The method of claim 33, wherein the first correction factor is proportional to a difference in density between the fluid in the sensor measuring portion and the fluid in the first fluid flow path, multiplied by the angle of inclination of the sensor measuring portion relative to the at least one reference axis, and divided by a mean viscosity of the fluid in the sensor measuring portion.

36. The method of claim 28, wherein the fluid flow path further includes a first fluid flow path and the sensor flow path, the sensor flow path being fluidly connected to the first fluid flow path, wherein the act of determining the angle of inclination includes an act of determining the angle of inclination of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to three orthogonal reference axes, and wherein the act of calculating includes acts of:

calculating a first correction factor that accounts for recirculation of fluid between the first fluid flow path and the sensor flow path and the determined angle of inclination of the sensor measuring portion relative to a first of the three orthogonal reference axes; and

calculating a second correction factor that accounts for differences in a density of the fluid in the sensor inlet portion and a density of the fluid in the sensor outlet portion, and the determined angle of inclination of the sensor inlet portion and the sensor outlet portion relative to a second of the three orthogonal reference axes.

37. The method of claim 36, wherein the sensor flow path is enclosed within a sensor flow path housing, and wherein the act of calculating further includes an act of:

calculating a third correction factor that accounts for convective effects between the sensor flow path housing and its surrounding environment, and the determined angle of inclination of at least one of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to at least one the three orthogonal reference axes.

38. The method of claim 37, wherein the act of determining the mass flow rate of the fluid flowing in the flow path includes an act of taking a product of the determined flow rate of the fluid flowing in the sensor measuring portion with the second correction factor, and adding a sum of the first and third correction factors to the product.