Sensor mounting for coriolis mass flow rate meter

• US 4,895,031 A
• Filed: 08/01/1988
• Issued: 01/23/1990
• Est. Priority Date: 08/29/1985
• Status: Expired due to Fees

• Current Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Original Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Inventors: Cage, Donald
• Primary Examiner(s): Goldstein, Herbert
• Application Number:
  US07/226,554
• Time in Patent Office: 540 Days
• Field of Search: 73/861.37, 73/861.38
• US Class Current: 73/861.355
• CPC Class Codes: G01F 1/8409 constructional details
• CPC Class Codes: G01F 1/8413 means for influencing the flowmeter's motional or vibrational behaviour, e.g., conduit support or fixing means, or conduit attachments
• CPC Class Codes: G01F 1/8418 motion or vibration balancing means
• CPC Class Codes: G01F 1/8427 detectors
• CPC Class Codes: G01F 1/8477 with multiple measuring conduits

Abstract

A Coriolis mass flow meter apparatus for determining the mass flow rates of fluids passed through twin flow tubes which are oscillated by a driver in a tuning fork fashion so as to be distorted by the mass flow rate of the fluid passing through the tubes with the distortion measured by sensors; where, sensor and driver components are mounted to each of the flow tubes so that the masses of the components and the structures used to mount the components to the flow tubes results in a center of gravity which is located on the axes about which each flow tube is distorted by generated Coriolis forces.

Claims

1. An apparatus for measuring the mass flow rate of a fluid having two flow conduits, each mounted for oscillation about an axis, of a length of each of said flow conduits through which the fluid to be measured is flowed, comprising:

(A) a first sensor means for detecting Coriolis force induced distortions of said flow conduits, said first sensor means having at least two sensor means components, said first sensor means components having essentially equal masses;

(B) a second sensor means for detecting Coriolis force induced distortions of said flow conduits, said second sensor means having at least two sensor means components, said second sensor means components having essentially equal masses;

(C) a first beam to which are attached at opposite ends a first sensor means component and a second sensor means component;

(D) a second beam, said beam having a mass essentially equal to that of said first beam, to which are attached at opposite ends of said second beam a first sensor means component and a second sensor means component;

(E) means for attaching said first beam to a first flow conduit so that the locations where said first beam is attached to said first flow conduit are at essentially equal first distances from the axis about which said first flow conduit is oscillated, and for attaching said first beam to said first flow conduit so that the center of gravity of said first beam in combination with said first and second sensor means components is essentially positioned on the axis about which generated Coriolis forces act; and

(F) means for attaching said second beam to a second flow conduit so that the locations where said second beam is attached to said second flow conduit are at essentially equal second distances from the axis about which said second flow conduit is oscillated, said first distances and said second distances being essentially equal, and for attaching said second beam to said second flow conduit so that the center of gravity of said second beam in combination with said first and second sensor means components is essentially positioned on the axis about which generated Coriolis forces act.

2. An apparatus as set forth in claim 1 in which a drive coil is attached in the middle of said first beam so that the center of gravity of said first beam in combination with said first and second sensor means components and said drive coil is essentially positioned on the axis about which generated Coriolis forces act, and a drive magnet, having a mass essentially equal to the mass of said drive coil, is attached in the middle of said second beam so that the center of gravity of said second beam in combination with said first and second sensor means components and said drive magnet is essentially positioned on the axis about which generated Coriolis forces act.

3. An apparatus as set forth in claim 1 in which said first sensor means includes a first sensor magnet and a first sensor coil, said first sensor coil and said first sensor magnet having essentially equal masses;

and,

said second sensor means includes a second sensor magnet and a second sensor coil, said second sensor coil and said second sensor magnet having essentially equal masses.

4. An apparatus as set forth in claim 3 in which only one pole of a sensor magnet enters a sensor coil and generates an electrical signal in said sensor coil.

5. An apparatus as set forth in claim 1 in which the locations of said first and second sensor means components are selected on both said first and second beams so that the resonant frequency of said first and second flow conduits about the axes where generated Coriolis forces act is higher than, and not a harmonic of, the resonant frequency of the axes about which said first and second flow conduits are driven in oscillation.

6. An apparatus as set forth in claim 4 in which the diameter of said sensor magnet is no more than one half the inside diameter of said sensor coil and the relative movement of said sensor magnet with respect to said sensor coil is no more than one half the longitudinal distance of said sensor coil.

7. In a method for constructing an apparatus for measuring the mass flow rate of a fluid comprising (1) two sensor systems each consisting essentially of two sensor components for detecting Coriolis forces and (2) two flow conduits, mounted to permit a length thereof to oscillate (a) about an axis for said flow conduit and (b) as one tine of a tuning fork in cooperation with the other flow conduit, the improvement which comprises

mounting one of the two sensor components from both sensor systems on each of two beam structures

and attaching one of the resulting beam structures with two sensor components mounted thereon to each of said flow conduits in a manner such that the aggregate center of gravity of each beam structure with mounted sensor components thereon lies (i) at an equal distance from the axis about which a length of the attached conduit oscillates and (ii) essentially on the axis of the attached flow conduit about which generated Coriolis forces act when fluid is flowing through the conduit.