Coriolis mass flow controller

• US 20030131668A1
• Filed: 01/27/2003
• Published: 07/17/2003
• Est. Priority Date: 12/08/1998
• Status: Active Grant

• Current Assignee: Emerson Electric Company
• Original Assignee: Emerson Electric Company
• Inventors: Whiteley, Jeffrey L., Dille, Joseph C., Barger, Michael J., Scott, Timothy W.
• Granted Patent: US 6,769,301 B2
• Time in Patent Office: Days
• US Class Current: 73/861.354
• CPC Class Codes: G01F 1/8404 details of flowmeter manufacturing methods
• CPC Class Codes: G01F 1/8422 exciters
• CPC Class Codes: G01F 1/8427 detectors
• CPC Class Codes: G01F 1/8436 signal processing
• CPC Class Codes: G01F 1/8445 micromachined flowmeters
• CPC Class Codes: G01F 1/8472 having curved measuring conduits, i.e. whereby the measuring conduits' curved center line lies within a plane G01F1/8481 takes precedence
• CPC Class Codes: G05D 7/0635 by action on throttling means G05D7/0688, G05D7/0694 take precedence

Abstract

A Coriolis mass flow sensor includes a flow sensor tube, a drive device situated relative to the flow sensor tube so as to cause the flow sensor tube to vibrate, and capacitance displacement gauges situated relative to the flow sensor tube so as to measure the twist in the flow sensor tube due to Coriolis force. In specific embodiments, electromagnetic, electrostatic, acoustic, and/or piezoelectric drives are used to vibrate the flow sensor tube. In still further embodiments, piezoelectric devices are used both to vibrate the flow sensor tube and measure the twist in the flow sensor tube. In accordance with certain embodiments of the invention, the Coriolis mass flow controller further includes an integrated flow control device adapted to receive fluid from the flow sensor tube and provide flow control.

Claims

1. A Coriolis mass flow sensor, comprising:

a flow sensor tube;

a drive device situated adjacent the flow sensor tube so as to cause the flow sensor tube to vibrate; and

at least one capacitance displacement gauge situated adjacent the flow sensor tube so as to measure the twist in the flow sensor tube due to Coriolis force, the at least one capacitance displacement gauge including first and second plates positioned side by side in a plane tangential to the motion of the flow sensor tube when the flow sensor tube is vibrated.

2. The Coriolis mass flow sensor of claim 1, wherein the drive device comprises an electromagnetic drive.

3. The Coriolis mass flow sensor of claim 1, wherein the drive device comprises an electrostatic drive.

4. The Coriolis mass flow sensor of claim 1, wherein the drive device comprises an acoustic drive.

5. The Coriolis mass flow sensor of claim 1, wherein the drive device comprises a piezoelectric drive.

6. The Coriolis mass flow sensor of claim 1, wherein the at least one capacitance displacement gauge comprises two capacitance displacement gauges.

7. The Coriolis mass flow sensor of claim 6, wherein the capacitance displacement gauges are situated at positions symmetric to the shape of the sensor tube.

8. The Coriolis mass flow sensor of claim 6, wherein the capacitance displacement gauges are surface mounted on a sensor package wall.

9. The Coriolis mass flow sensor of claim 1, further comprising a circuit for measuring phase shift caused by the Coriolis force.

10. The Coriolis mass flow sensor of claim 9, wherein the circuit includes a lock-in amplifier.

11. The Coriolis mass flow sensor of claim 1, wherein the at least one capacitance displacement gauge is mounted on an actuator, wherein the actuator positions the capacitance displacement gauge in relation to the flow sensor tube.

12. The Coriolis mass flow sensor of claim 11, wherein the actuator comprises a piezoelectric actuator.

13. The Coriolis mass flow sensor of claim 11, wherein the actuator positions the at least one capacitance displacement gauge in response to flow conditions.

14. The Coriolis mass flow sensor of claim 11, wherein the actuator positions the at least one capacitance displacement gauge in three dimensions.

15. The Coriolis mass flow sensor of claim 1, wherein the first and second plates define a uniform gap therebetween.

16. The Coriolis mass flow sensor of claim 15, wherein the first and second plates are at the same potential and the flow sensor tube is at ground potential.

17. The Coriolis mass flow sensor of claim 15, wherein the first and second plates are generally rectangular and the gap extends generally parallel to the flow sensor tube.

18. The Coriolis mass flow sensor of claim 15, wherein the first and second plates are generally triangular and the gap extends diagonally across the flow sensor tube.

19. The Coriolis mass flow sensor of claim 15, wherein the first and second plates are generally saw-tooth shaped, and the gap defines a generally saw-tooth shape.

20. The Coriolis mass flow sensor of claim 1, further comprising an evacuated housing, the flow sensor tube being positioned within the evacuated housing.

21. A Coriolis mass flow sensor, comprising:

a flow sensor tube having first and second ends; and

first and second piezoelectric stacks positioned on the respective first and second ends of the flow sensor tube;

wherein the piezoelectric and reverse piezoelectric effects cause the flow sensor tube to vibrate and sense the twist in the flow sensor tube due to Coriolis force.

22. A Coriolis mass flow controller, comprising:

a flow sensor tube;

a drive device situated adjacent the flow sensor tube so as to cause the flow sensor tube to vibrate;

a position sensing device situated adjacent the flow sensor tube so as to measure the twist in the flow sensor tube due to Coriolis force;

a flow control device adapted to receive fluid from the flow sensor tube; and

a processor coupled to the position sensing device and the flow control device, the processor receiving an indication of a desired mass flow rate, wherein the processor is programmed to determine the actual mass flow rate based on the measured twist in the flow sensor tube due to Coriolis force, and manipulate the flow control device in response to the desired mass flow rate and the actual mass flow rate.

23. The Coriolis mass flow controller of claim 22, wherein the flow control device comprises a valve, the valve including:

a valve seat;

a plunger adapted to seal against the valve seat, the plunger defining at least one hole extending therethrough so as to establish a fluid flow path through the plunger when the plunger is unseated from the valve seat.

24. The Coriolis mass flow controller of claim 22, wherein the flow control device comprises a pump.

25. The Coriolis mass flow controller of claim 24, wherein the pump comprises a metering pump.

26. A method of determining mass flow from a Coriolis force-induced phase shift between first and second input signals detected by first and second displacement gauges, comprising:

mixing the first input signal with the second input signal to produce a first output signal;

phase shifting the first input signal 90°

;

mixing the second input signal with the phase shifted first input signal to produce a second output signal; and

calculating the vector magnitude and phase of the first and second output signals relative to each other, wherein the vector phase is proportional to mass flow.

27. The method of claim 26, further comprising filtering the first and second output signals.

28. The method of claim 26, further comprising phase locking a driver terminal to the first input signal to drive a flow tube at resonance.

29. The method of claim 26, wherein mixing the first and second input signals comprises inputting the first and second input signals to a phase sensitive detector.

30. The method of claim 26, wherein mixing the first and second input signals comprises mixing the difference between the first and second input signals with the first input signal.

31. A device for determining mass flow from a Coriolis force-induced phase shift between first and second input signals detected by first and second displacement gauges, comprising:

a differential amplifier coupled to the first and second displacement gauges to receive the first and second input signals, the differential amplifier operable to output a signal representing the difference between the first and second input signals;

a first phase sensitive detector coupled to the differential amplifier and the first displacement gauge to receive the output of the differential amplifier and the first input signal and provide an output representing the mixed differential amplifier signal and the first input signal;

a phase shifter coupled to the first displacement gauge to receive the first input signal and operable to output a signal representing the first input signal phase shifted 90°

;

a second phase sensitive detector coupled to the phase shifter and the differential amplifier to receive the phase shifter output and the differential amplifier signal and provide an output representing the mixed phase shifted first input signal and the differential amplifier signal, and provide an output representing the mixed signals; and

a processor coupled to the first and second phase sensitive detectors to receive the mixed signals and operable to calculate the vector magnitude and phase of the mixed signals relative to each other, wherein the vector phase is proportional to mass flow.

32. The device of claim 31, further comprising first and second low pass filters coupled to the first and second phase sensitive detectors, the first and second low pass filters operable to remove high frequency components from the mixed signals and output DC voltages.

33. The device of claim 31, further comprising a third output terminal phase locked to the first input terminal for providing a sinusoidal output signal to drive a flow tube to resonance.

34. The device of claim 31, wherein the device comprises a lock-in amplifier.

35. A Coriolis mass flow sensor, comprising:

a flow sensor tube;

an evacuated housing, the flow sensor tube being positioned within the evacuated housing;

a drive device situated adjacent the flow sensor tube so as to cause the flow sensor tube to vibrate; and

at least one capacitance displacement gauge situated adjacent the flow sensor tube so as to measure the twist in the flow sensor tube due to Coriolis force.

36. A Coriolis mass flow sensor, comprising:

a flow sensor tube;

a drive device situated adjacent the flow sensor tube so as to cause the flow sensor tube to vibrate; and

at least one capacitance displacement gauge mounted on an actuator adjacent the flow sensor tube for measuring the twist in the flow sensor tube due to Coriolis force, the actuator dynamically positioning the capacitance displacement gauge in relation to the flow sensor tube.

37. The Coriolis mass flow sensor of claim 36, wherein the actuator comprises a piezoelectric actuator.

38. The Coriolis mass flow sensor of claim 36, wherein the actuator positions the at least one capacitance displacement gauge in response to flow conditions.

39. The Coriolis mass flow sensor of claim 36, wherein the actuator positions the at least one capacitance displacement gauge in three dimensions.