Mode split resonator for a coriolis flowmeter balance bar

Abstract

A mode separator (300) for a balance bar (150) of a Coriolis flowmeter (100) is disclosed. The mode separator (300) includes a mass portion (302) and a first coupling portion (304a) coupled to the mass portion (302). The first coupling portion (304a) has a first stiffness in a drive direction (Y) and a second stiffness in an orthogonal direction (Z), and the orthogonal direction (Z) is orthogonal to both the drive direction (Y) and a longitudinal direction of the balance bar (150). The second stiffness is different than the first stiffness.

Description

TECHNICAL FIELD

[0001] The implementations described below relate to Coriolis flowmeter balance bars, and more specifically, to separating modes of Coriolis flowmeter balance bars. BACKGROUND

[0002] Coriolis flowmeters are a type of flowmeter that can be used to measure mass flow rate, density, volumetric flow rate, and other information about a process fluid. Coriolis flowmeters can include a single flow tube with one or more associated balance bars, two flow tubes, or any other number of flow tubes. The vibrating structure of a Coriolis flowmeter is typically a dynamic balance system. For example, when a Coriolis flowmeter includes a pair of flow tubes, the flow tubes can vibrate in phase opposition to form a dynamic balance system. However, in Coriolis flowmeters that include a single flow tube, the flow tube typically vibrates in phase opposition with a balance bar to form a dynamic balance system. However, in further implementations, Coriolis flowmeters with more than one flow tube can include balance bars to provide a dynamic balance system.

[0003] Figure 1 An example Coriolis flowmeter 100 with a straight flow tube 130 is depicted. The Coriolis flowmeter 100 can include a housing 102. Struts 140, 140' can couple the flow tube 130 to the flowmeter housing 102. The struts 140 and 140' can also help define the axis about which the flow tube 130 oscillates.

[0004] Flanges 103 and 103' are connected via inlet end 104 and outlet end 104' to a process conduit (not shown) that carries the fluid being measured.

[0005] The Coriolis flowmeter 100 also includes a driver 180 that oscillates the flow tube 130. The driver 180 can include any of a number of well-known devices, such as a magnet mounted to the flow tube 130 and an opposing coil mounted to the bracket 161, 161' using brazing, adhesive, fasteners, or any other coupling method known to those skilled in the art. However, in further implementations, any portion of the driver 180 can be mounted to the balance bar 150, 150', or any other structure known to those skilled in the art. An alternating current driver current is passed through the driver 180 to vibrate the flow tube 130. In the example Coriolis flowmeter 100, the drive direction is in the y-direction, which is vertical in the figure. Figure 1

[0006] ​The Coriolis flowmeter 100 also includes a pair of pickoff sensors 170L and 170R. The pickoff sensors 170L and 170R can include any of a number of well-known velocity, displacement, or acceleration pickoff sensor arrangements, such as a magnet mounted to the flow tube 130 and an opposing coil mounted to the support 160L, 160R. However, in further embodiments, any portion of the pickoff sensors 170L and 170R can be mounted to the balance bar 150, 150', or to any other structure by use of brazing, adhesives, fasteners, or any other coupling method known to those of skill in the art. The pickoff sensors 170L and 170R measure the displacement of the flow tube 130 as it vibrates. In the absence of flow through the flow tube 130, the signals of the pickoff sensors 170L and 170R are in phase. However, once flow begins through the vibrating tube, a Coriolis force is generated on the tube. In the example Coriolis flowmeter 100, the pickoff sensors 170L and 170R determine the motion of the flow tube 130 in the drive direction or Y direction.

[0007] Meter electronics (not depicted) provide drive signals to the driver 180 to vibrate the flow tube 130, receive left and right velocity signals from the velocity pickoff sensors 170L and 170R, and calculate mass flow rate, volume flow rate, and / or density information for the flow through the Coriolis flowmeter 100.

[0008] The example Coriolis flowmeter 100 includes balance bars 150, 150' that serve to dynamically balance the oscillation of the flow tube 130. Each of the balance bars 150, 150' extends in a longitudinal direction parallel to the axis of the flow tube 130, and both balance bars 150, 150' are positioned along opposite sides of the flow tube 130. In the example Coriolis flowmeter 100, the balance bars 150, 150' are positioned in the Z direction on opposite sides of the flow tube 130. The balance bars 150, 150' are configured to oscillate in opposition to the flow tube 130. However, in further embodiments, the Coriolis flowmeter 100 can include only one balance bar, or any number of balance bars known to those of skill in the art. In further embodiments, the balance bars 150, 150' can be coupled to the flow tube 130 in different orientations.

[0009] The balance bars 150, 150' of the example Coriolis flowmeter 100 are connected to each other via one or more supports 160L, 160R, 161, and 161'. However, in further embodiments, different arrangements of supports are possible, as will be appreciated by those of skill in the art.

[0010] In the example Coriolis flowmeter 100, the cross-section of the balance bar 150 is substantially square. This can be in Figure 2It is observed that, Figure 2 A cross-section of the balance bar 150 is depicted including a Y-direction and a Z-direction, the Y-direction aligned with the drive direction and the Z-direction orthogonal to the drive direction. By substantially square, it is meant that the lengths of the balance bar 150 in the Y-direction and the Z-direction are within 15% of each other. However, in further embodiments, the lengths of the balance bar 150 in the Y-direction and the Z-direction can be within 10% or 5% of each other.

[0011] The substantially square cross-sectional shape of the balance bar 150 provides substantially the same stiffness in the Y-direction and the Z-direction. When the balance bar 150 moves in phase opposition to the flow tube 130, the example balance bar 150 tends to have a natural frequency in the Y-direction that is substantially the same as the natural frequency in the Z-direction. For example, using finite element analysis modeling for one balance bar design in an out-of-phase mode, the natural frequency in the Y-direction or drive direction was determined to be about 498 Hz, or substantially equal to the natural frequency in the Z-direction of 503 Hz. When the natural frequencies in both the Y-direction and the Z-direction are substantially the same or within 5% of each other, there can be an undesirable response from the Z-direction detected in the Y-direction by the pickoff sensors 170R, 170L. This can reduce the accuracy of the Coriolis flow meter measurement.

[0012] Because meter accuracy is sensitive to the cross-sectional dimensions of the balance bar 150, it is difficult to change the substantially square dimensions of the balance bar 150 cross-section without affecting the performance of the flow meter. Specifically, if the balance bar 150 is too narrow in the Z-direction, the sensitivity of the flow meter to density can be affected. However, if the balance bar 150 is too wide in the Z-direction, the vibration in the Z-direction can ground and thus be equal to the balanced Y-direction mode. To this end, it is challenging to decouple the vibrations between the orthogonal modes of an existing Coriolis flow meter balance bar, and thus some existing flow meters can have reduced accuracy.

[0013] The balance bar 150 provides just one example of a balance bar cross-sectional shape that can create noise cross-coupling between the Y-direction and the Z-direction. In further embodiments, a balance bar having a different cross-sectional shape can have substantially the same stiffness characteristics in the Y-direction and the Z-direction, making noise cross-coupling between the Y-direction and the Z-direction more likely.

[0014] Further needed is a method to prevent noise cross-coupling between the Y-direction and the Z-direction in a balance bar to improve the accuracy of a Coriolis flow meter. SUMMARY

[0015] A mode separator for a balance bar or flow tube of a Coriolis flowmeter is provided according to a first embodiment. The mode separator includes a mass portion and a first coupling portion coupled to the mass portion. The first coupling portion has a first stiffness in a drive direction and a second stiffness in an orthogonal direction, the orthogonal direction being orthogonal to both the drive direction and a longitudinal direction of the balance bar, the second stiffness being different than the first stiffness.

[0016] A Coriolis flowmeter is provided according to a second embodiment. The Coriolis flowmeter includes a flow tube, a driver configured to oscillate the flow tube, at least one pickoff sensor configured to measure motion of the flow tube, a first balance bar, and a first mode separator coupled to at least one of the first balance bar or the flow tube. The first mode separator includes a mass portion and a first coupling portion coupled to the mass portion, wherein the first coupling portion has a first stiffness in a drive direction and a second stiffness in an orthogonal direction, the orthogonal direction being orthogonal to both the drive direction and a longitudinal direction of the balance bar, the second stiffness being different than the first stiffness.

[0017] A method for assembling a Coriolis flowmeter is provided according to a third embodiment. The method includes providing a flow tube, coupling a driver configured to oscillate the flow tube to the flow tube, coupling at least one pickoff sensor configured to measure motion of the flow tube to the flow tube, coupling a brace bar to the flow tube, coupling a balance bar to the brace bar, and coupling a mode separator to at least one of the flow tube or the balance bar. The mode separator includes a mass portion and a first coupling portion coupled to the mass portion, wherein the first coupling portion has a first stiffness in a drive direction and a second stiffness in an orthogonal direction, the orthogonal direction being orthogonal to both the drive direction and a longitudinal direction of the balance bar, the second stiffness being different than the first stiffness.

[0018] Aspects

[0019] According to an aspect, the second stiffness can be greater than the first stiffness.

[0020] According to an aspect, the mass portion can have a first end and a second end at opposite ends of the mass portion, the first coupling portion can be coupled to the first end of the mass portion, and the mode separator can further include a second coupling portion coupled to the second end of the mass portion.

[0021] According to an aspect, the second coupling portion can have a third stiffness in the drive direction and a fourth stiffness in the orthogonal direction, the fourth stiffness being greater than the third stiffness.

[0022] According to an aspect, the first coupling portion can have a second dimension in the orthogonal direction, the second dimension being substantially greater than a first dimension in the drive direction.

[0023] According to an aspect, the second stiffness can be greater than the first stiffness.

[0024] According to an aspect, the mass portion can have a first end and a second end at opposite ends of the mass portion, the first coupling portion can be coupled to the first end of the mass portion, and the mode separator can further include a second coupling portion coupled to the second end of the mass portion.

[0025] According to an aspect, the second coupling portion can have a third stiffness in the drive direction and a fourth stiffness in the orthogonal direction, the fourth stiffness being greater than the third stiffness.

[0026] According to an aspect, the first coupling portion can have a second dimension in the orthogonal direction, the second dimension being substantially greater than a first dimension in the drive direction.

[0027] According to an aspect, the first mode separator can be configured to provide a combined first balance bar and first mode separator natural frequency in the orthogonal direction that is at least five percent lower than a first balance bar natural frequency in the orthogonal direction without the mode separator.

[0028] According to an aspect, the first mode separator can be configured to provide a combined first balance bar and first mode separator natural frequency in the orthogonal direction that is at least ten percent lower than a first balance bar natural frequency in the orthogonal direction without the mode separator.

[0029] According to an aspect, the mode separator can be configured to have a combined first balance bar and mode separator natural frequency in the drive direction that is within one percent of a first balance bar natural frequency in the drive direction without the mode separator.

[0030] According to an aspect, the first balance bar can have a substantially square cross-sectional area.

[0031] According to an aspect, the Coriolis flowmeter can further include a second balance bar coupled to the first balance bar using one or more brackets.

[0032] According to an aspect, the Coriolis flowmeter can further include a second balance bar and a second mode separator coupled to at least one of the flow tube or the second balance bar.

[0033] According to an aspect, the flow tube can be straight.

[0034] According to an aspect, the step of coupling the balance bar to the brace bar can further include coupling a first balance bar to the brace bar, coupling a second balance bar to the brace bar, and coupling the first balance bar to the second balance bar using one or more brackets. BRIEF DESCRIPTION OF DRAWINGS

[0035] In all of the drawings, like reference numerals refer to like elements throughout. It is understood that the drawings are not necessarily to scale.

[0036] Figure 1 A Coriolis flowmeter 100 according to an embodiment is depicted;

[0037] Figure 2 A balance bar 150 according to an embodiment is depicted;

[0038] Figure 3 A mode separator 300 according to an embodiment is depicted;

[0039] Figure 4 A graph 400 according to an embodiment is depicted;

[0040] Figure 5 A method 500 according to an embodiment is depicted; and

[0041] Figure 6 A method 600 according to an embodiment is depicted. DETAILED DESCRIPTION

[0042] Figures 1 to 6 The following description depicts specific examples to teach those skilled in the art how to make and use the best mode of the application. Some conventional aspects have been simplified or omitted for the sake of clarity. Those skilled in the art will appreciate variations from these examples that fall within the scope of the present application. Those skilled in the art will appreciate that the features described below can be combined in various ways to form many variations of the present application. Therefore, the application is not limited to the specific examples described below, but only by the claims and their equivalents.

[0043] Figure 3 A mode separator 300 according to an embodiment is depicted. The mode separator 300 can be coupled to at least one of the flow tube 130 or the balance bar 150, 150' of the Coriolis flowmeter 100 to decouple the vibration between the vibration modes in the drive direction and the vibration modes in the orthogonal direction.

[0044] The mode separator 300 includes a mass portion 302 and a first coupling portion 304a. The mass portion 302 includes a central body of the mode separator. In the example of the mode separator 300, the mass portion 302 has a cylindrical shape with a diameter of 1 inch and a height of 1 inch. However, this is not intended to be limiting. In further embodiments, the mass portion 302 can include any size or shape, as will be appreciated by those of skill in the art.

[0045] In embodiments, the mass portion 302 can be formed of a high density material, such as tungsten. However, in further embodiments, the mass portion 302 can be formed of any material known to those of skill in the art.

[0046] The first coupling portion 304a is coupled to the mass portion 302. The first coupling portion 304a is configured to couple the mass portion 302 to the balance bar 150, or a fixture that is coupled to the balance bar 150. The first coupling portion 304a is coupled to the mass portion 302 at a first end, and the first coupling portion 304a is coupled to the balance bar 150, or the flow meter fixture, at a second end opposite the first end.

[0047] The first coupling portion 304a has a first stiffness in a drive direction and a second stiffness in an orthogonal direction that is orthogonal to both the drive direction and a longitudinal direction of the balance bar, and the second stiffness is greater than the first stiffness. In Figure 3 In the example, it can be seen that the drive direction is in the Y direction, the longitudinal direction following the length of the balance bar 150 and the flow tube 130 is in the X direction, and the orthogonal direction is in the Z direction.

[0048] In embodiments, the first coupling portion 304a can be cut from a sheet of stainless steel, such as 304SS. However, in further embodiments, the first coupling portion 304a can include any material known to those of skill in the art, and include any configuration that allows the second stiffness in the orthogonal direction Z to be greater than the first stiffness in the drive direction Y.

[0049] In embodiments of the mode separator 300, the first coupling portion 304a comprises a flat rectangular piece having two flat faces. In embodiments, the first coupling portion 304a can be 0.5 inches long in the longitudinal direction X, 1.5 inches long in the orthogonal direction Z, and 0.024 inches thick in the drive direction Y. By providing the first coupling portion 304a much longer in the drive direction Y than in the orthogonal direction Z, the first coupling portion 304a can be configured to behave differently in the orthogonal direction Z than in the drive direction Y. In embodiments of the mode separator 300, the first coupling portion 304a is configured to be stiffer in the orthogonal direction Z than in the drive direction Y. However, in further embodiments, the first coupling portion 304a can comprise any configuration that allows a second stiffness in the orthogonal direction Z to be different than a first stiffness in the drive direction Y. For example, the first coupling portion 304a can comprise a carbon fiber composite material, where the fibers are arranged so as to provide a second stiffness in the orthogonal direction Z that is greater than a first stiffness in the drive direction Y.

[0050] In embodiments, the first coupling portion 304a and the mass portion 302 can be formed as a single unitary body. However, in further embodiments, the first coupling portion 304a and the mass portion 302 can be formed as separate portions that are coupled together.

[0051] In coupling the mode separator 300 to the flow tube 130 or the balance bar 150, the mass portion 302 is weakly coupled to the flow tube 130 or the balance bar 150 in the drive direction Y and strongly coupled to the flow tube 130 or the balance bar 150 in the orthogonal direction. This can help to isolate vibrations from the orthogonal mode in the Z direction from vibrations from the drive mode in the Y direction, thereby improving metering accuracy.

[0052] In embodiments, the mass portion 302 has a first end and a second end at opposite ends. In Figure 3 In embodiments of the mode separator 300, it can be seen that the mass portion 302 has a first end 306a and a second end 306b at opposite ends of a cylindrical piece that forms a body of the mass portion 302. The first coupling portion 304a is coupled to the first end 306a of the mass portion 302.

[0053] In embodiments, the mode separator 300 can further comprise a second coupling portion coupled to the second end of the mass portion. For example, as in Figure 3As can be seen, the second coupling portion 304b can be coupled to the second end 306b of the mass portion 302. In embodiments, the second coupling portion 304b can be similar in form and features to the first coupling portion 304a. By providing the mode separator 300 with two coupling portions 304a, 304b positioned at opposite ends 306a, 306b of the mass portion 302, a balanced mode separator 300 can be provided that can separate and split the quadrature mode frequency and the drive mode frequency, and reduce the non-resonant response of the Z-mode at the drive frequency.

[0054] In embodiments, the second coupling portion 304b can have a third stiffness in the drive direction Y and a fourth stiffness in the quadrature direction Z, the fourth stiffness being greater than the third stiffness. In embodiments, the third stiffness can be the same as the first stiffness, and the fourth stiffness can be the same as the second stiffness.

[0055] In embodiments, the first coupling portion 304a can include a second dimension in the quadrature direction Z that is substantially greater than a first dimension in the drive direction Y. For example, as can be seen in the embodiment of Figure 3 As can be seen in the embodiment of

[0056] Figure 4 It is illustrated how the mode separator 300 can help to separate the drive mode from the quadrature mode. Figure 4 A graph 400 is depicted that provides the ratio of output displacement to input displacement, or the transmissibility, as a function of frequency for the drive direction Y and the quadrature direction Z at the location where the mode separator 300 is coupled to the balance bar 150. For example, in Figure 3 As can be seen in the embodiment of

[0057] Figure 4The frequency response of the mode separator 300 to vertical (drive direction of the flowmeter, Y direction) and horizontal input (Z direction of the flowmeter) is illustrated, where the mode separator 300 is attached to the balance bar 150. As can be seen, the drive transfer rate curve 402 has a large peak at 164 Hz. By providing a mode separator 300 having a frequency response peak at 164 Hz, when the mode separator 300 is coupled to the flow tube 130 or balance bar 150, the mode separator 300 can lower the natural frequency of the balance bar 150 in the drive direction Y below the drive frequency of 500 Hz. In embodiments, the mode separator 300 can be configured to provide a drive transfer rate curve 402 having an even lower frequency peak. For example, if the mass of the mass portion 302 is increased, the drive transfer rate curve 402 can provide an even lower frequency response peak.

[0058] From Figure 4 As can be readily seen, the drive transfer rate curve 402 responds at frequencies well below resonance without amplification and is therefore in phase. However, above resonance, the drive transfer rate curve 402 decays rapidly as the input energy loses its ability to move the mass of resonance. In embodiments, the drive transfer rate curve 402 can provide a peak response frequency below the frequency of the drive mode in the drive direction Y. In this manner, the motion of the mode separator 300 in the drive mode in the drive direction Y can be damped.

[0059] The graph 400 depicts the quadrature transfer rate curve 404 having a peak frequency (not depicted in Figure 4 ) well above the drive frequency of 500 Hz at approximately 5000 Hz. This can allow the mode separator 300 to move in phase with the balance bar 150 in the quadrature direction Z (as a rigid attachment), thereby providing a lower bending frequency in the quadrature direction Z once the mode separator 300 is attached to the balance bar 150 (due to the additional mass of the rigid coupling).

[0060] In embodiments, the first mode separator 300 can be coupled to a flow tube or a first balance bar of a Coriolis flowmeter. For example, the first mode separator 300 can be coupled to the Coriolis flowmeter 100 including a flow tube 130, a driver 180 configured to oscillate the flow tube 130, at least one pickoff sensor 170R, 170L configured to measure motion of the flow tube 130, and a balance bar 150 as described above.

[0061] In embodiments, the first mode separator 300 can be coupled to a central longitudinal position of the flow tube 130 or the balance bar 150 such that the drive direction Y of the first mode separator 300 is aligned with the drive direction of the Coriolis flow meter 100. In embodiments, the first mode separator 300 can be positioned adjacent to the driver 180. However, in further embodiments, the first mode separator 300 can be coupled along any other longitudinal portion of the flow tube 130 or the balance bar 150, as will be appreciated by those skilled in the art.

[0062] For example, in Figure 1 It can be seen in FIG. 1 that the balance bar 150 includes a first coupling location 180a on a face of the balance bar 150 that faces the driver 180. The balance bar 150 can also include a second coupling location 180b, not visible in the figure, positioned underneath the balance bar 150 to face in an opposite direction from the driver 180. In embodiments, the mode separator 300 can be coupled to the balance bar 150 between the first and second coupling locations 312a and 180a and 312b and 180b via any method known to those skilled in the art, including but not limited to brazing or using an adhesive. However, examples of the Coriolis flow meter 100 are not intended to be limiting. In further embodiments, the mode separator 300 can be coupled to the balance bar 150 at a single point or more than two points. Furthermore, the mode separator 300 can be coupled to different faces of the balance bar 150.

[0063] In embodiments, the first balance bar 150 and the first coupling portion 304a can have a combined first stiffness in the drive direction Y and a combined second stiffness in the orthogonal direction Z, the second stiffness being different from the first stiffness. In embodiments, the second stiffness can be greater than the first stiffness. This can further provide decoupling between the orthogonal mode vibrations and the drive mode vibrations.

[0064] In embodiments, the first mode separator 300 can be configured to provide a combined first balance bar and first mode separator natural frequency in the orthogonal direction Z that is at least 5% lower than a first balance bar without a mode separator natural frequency in the orthogonal direction Z. However, in further embodiments, the combined first balance bar and first mode separator natural frequency in the orthogonal direction Z can be at least 10% or 15% lower than the first balance bar without a mode separator natural frequency in the orthogonal direction Z.

[0065] For example, in the example provided above, where the balance bar 150 has a natural frequency of 503 Hz in the orthogonal direction Z, and the mode coupler 300 provides a frequency response peak at 164 Hz in the orthogonal direction Z, the combined first balance bar and first mode decoupler natural frequency in the orthogonal direction Z can be 452 Hz, or approximately 11% lower than the natural frequency of the balance bar 150 in the orthogonal direction Z.

[0066] In embodiments, the mode decoupler can be configured to have a combined first balance bar and mode decoupler natural frequency in the drive direction that is within 1% of the natural frequency of the first balance bar without the mode decoupler in the drive direction.

[0067] For example, in the same example provided above, the balance bar 150 has a natural frequency of 497 Hz in the drive direction Y, and the mode decoupler 300 provides a frequency response peak at 5000 Hz in the drive direction Y. Thus, the combined first balance bar and first mode decoupler natural frequency in the drive direction Y can be 505 Hz, which is substantially the same as the 497 Hz natural frequency of the balance bar 150 in the drive direction Y.

[0068] In this way, the mode decoupler 300 can help isolate vibrations from the drive mode of the balance bar 150 from vibrations of the orthogonal mode.

[0069] In further embodiments, a second balance bar can be coupled to the first balance bar using one or more brackets. For example, Figure 1 A second balance bar 150' is depicted coupled to the first balance bar 150 via brackets 160L, 160R, 161, 161'. The second balance bar 150' can also be coupled to the flow tube 130 via struts 140, 140'.

[0070] In the example of the Coriolis flow meter 100, the brackets 160L and 160R also provide mounts for the first pickoff sensor 170R and the second pickoff sensor 170L, and the brackets 161, 161' also provide mounts for the driver 180. However, this is not intended to be limiting. As will be readily understood by those of skill in the art, one or more brackets 160L, 160R, 161, 161' can be coupled to any location along the longitudinal length of the balance bars 150, 150', and can or can not provide mounts for other flow meter components.

[0071] In embodiments, the Coriolis flowmeter 100 can also include a second balance bar 150' and a second mode separator 300 coupled to the flow tube 130 or the second balance bar 150'. In embodiments, the coupling between the flow tube 130 or the second balance bar 150' and the second mode separator 300 can be similar to or different from the coupling described above for the flow tube 130 or the first balance bar 150 and the first mode separator 300.

[0072] Figure 5 A method 500 according to embodiments is depicted. The method 500 can be used to assemble a Coriolis flowmeter 100. The method 500 begins with step 502. In step 502, a flow tube is provided. For example, the flow tube 130 can be provided as described above.

[0073] The method 500 continues with step 504. In step 504, a driver configured to oscillate the flow tube is coupled to the flow tube. For example, the driver 180 can be provided as described above.

[0074] The method 500 continues with step 506. In step 506, at least one pickoff sensor configured to measure motion of the flow tube is coupled to the flow tube. For example, the pickoff sensors 170R, 170L can be coupled to the flow tube 130 as described above.

[0075] The method 500 continues with step 508. In step 508, a brace bar is coupled to the flow tube. For example, the brace bar 140 can be coupled to the flow tube 130 as described above.

[0076] The method 500 continues with step 510. In step 510, a balance bar is coupled to the brace bar. For example, the balance bar 150 can be coupled to the brace bar 140 as described above.

[0077] Figure 6 A method 600 according to embodiments is depicted. In embodiments, step 510 can also include the steps of the method 600. The method 600 begins with step 602. In step 602, a first balance bar can be coupled to the brace bar. For example, the first balance bar 150 can be coupled to the brace bar 140 as described above.

[0078] The method 600 continues with step 604. In step 604, a second balance bar can be coupled to the brace bar. For example, the second balance bar 150' can be coupled to the brace bar 140 as described above.

[0079] The method 600 continues with step 606. In step 606, the first balance bar can be coupled to the second balance bar using one or more brackets. For example, the first balance bar 150 can be coupled to the second balance bar 150’ using one or more brackets 160L, 160R, 161, 161’ as described above.

[0080] The method 500 continues with step 512. In step 512, the mode separator is coupled to at least one of the flow tube or the balance bar. For example, the mode separator 300 can be coupled to the balance bar 150 as described above.

[0081] Thus, although particular embodiments have been described herein for purposes of illustration, various equivalent modifications can be made in the scope of the specification. The teachings provided herein can be applied to other embodiments without departing from the scope of this description. Accordingly, the scope of the embodiments described above should be determined from the following claims.

Claims

1. A mode separator (300) for connection to a balance bar (150) or flow tube (130) of a Coriolis flow meter (100), the mode separator (300) comprising: Quality section (302); as well as A first connecting portion (304a) includes a first end connected to the mass portion (302), wherein the first connecting portion (304a) has a first stiffness in the driving direction (Y) and a second stiffness in an orthogonal direction (Z), the orthogonal direction (Z) being orthogonal to both the driving direction (Y) and the longitudinal direction of the balance bar (150), and the second stiffness being different from the first stiffness.

2. The pattern separator (300) according to claim 1, wherein, The second stiffness is greater than the first stiffness.

3. The pattern separator (300) according to claim 1 or claim 2, wherein, The mass portion (302) has a first end (306a) and a second end (306b) at opposite ends, the first connecting portion (304a) is connected to the first end (306a) of the mass portion (302), and the mode separator (300) further includes: The second connecting portion (304b) is connected to the second end (306b) of the mass portion (302).

4. The pattern separator (300) according to claim 3, wherein, The second connecting portion (304b) has a third stiffness in the driving direction (Y) and a fourth stiffness in the orthogonal direction (Z), the fourth stiffness being greater than the third stiffness.

5. The pattern separator (300) according to claim 1 or claim 2, wherein, The first connecting portion (304a) has a second dimension (310) in the orthogonal direction (Z), which is significantly larger than the first dimension (308) in the driving direction (Y).

6. A Coriolis flow meter (100), comprising: Flow tube (130); A driver (180) configured to oscillate the flow tube (130); At least one pickup sensor (170L, 170R) is configured to measure the movement of the flow tube (130); First balance bar (150); and A first mode separator (300) is connected to at least one of the first balance bar (150) or the flow tube (130), the first mode separator (300) comprising: Quality section (302); and A first connecting portion (304a) includes a first end connected to the mass portion (302), wherein the first connecting portion (304a) has a first stiffness in the driving direction (Y) and a second stiffness in an orthogonal direction (Z), the orthogonal direction (Z) being orthogonal to both the driving direction (Y) and the longitudinal direction of the balance bar (150), and the second stiffness being different from the first stiffness.

7. The Coriolis flow meter (100) according to claim 6, wherein, The second stiffness is greater than the first stiffness.

8. The Coriolis flow meter (100) according to any one of claims 6 to 7, wherein, The mass portion (302) has a first end (306a) and a second end (306b) at opposite ends, the first connecting portion (304a) is connected to the first end (306a) of the mass portion (302), and the mode separator (300) further includes: The second connecting portion (304b) is connected to the second end (306b) of the mass portion (302).

9. The Coriolis flow meter (100) according to claim 8, wherein, The second connecting portion (304b) has a third stiffness in the driving direction (Y) and a fourth stiffness in the orthogonal direction (Z), the fourth stiffness being greater than the third stiffness.

10. The Coriolis flow meter (100) according to claim 6, wherein, The first connecting portion (304a) has a second dimension (310) in the orthogonal direction (Z), which is significantly larger than the first dimension (308) in the driving direction (Y).

11. The Coriolis flow meter (100) according to claim 6, wherein, The first mode separator (300) is configured to provide a combination of the natural frequencies of the first balance bar and the first mode separator in the orthogonal direction (Z), wherein the natural frequencies of the first balance bar and the first mode separator in the orthogonal direction (Z) are at least five percent lower than the natural frequency of the first balance bar without a mode separator in the orthogonal direction (Z).

12. The Coriolis flow meter (100) according to claim 6, wherein, The first mode separator (300) is configured to provide a combination of the natural frequencies of the first balance bar and the first mode separator in the orthogonal direction (Z), wherein the natural frequencies of the first balance bar and the first mode separator in the orthogonal direction (Z) are at least 10 percent lower than the natural frequency of the first balance bar without a mode separator in the orthogonal direction (Z).

13. The Coriolis flow meter (100) according to claim 6, wherein, The first mode separator (300) is configured to have a combination of the natural frequency of the first balance bar and the mode separator in the drive direction (Y), the natural frequency of the first balance bar and the mode separator in the drive direction (Y) being within one percent of the natural frequency of the first balance bar without the mode separator in the drive direction (Y).

14. The Coriolis flow meter (100) according to claim 6, wherein, The first balance bar (150) has a substantially square cross-sectional area.

15. The Coriolis flow meter (100) according to claim 6, wherein the Coriolis flow meter (100) further comprises a second balance bar (150'), the second balance bar (150') being connected to the first balance bar (150) by means of one or more brackets (160L, 160R, 161, 161').

16. The Coriolis flow meter (100) according to claim 6, the Coriolis flow meter (100) further comprising a second balance bar (150') and a second mode separator (300), the second mode separator (300) being connected to at least one of the flow tube (130) or the second balance bar (150').

17. The Coriolis flow meter (100) according to claim 6, wherein, The flow tube (130) is straight.

18. A method for assembling a Coriolis flow meter (100), the method comprising: Provide flow tube (130); A driver (180) configured to oscillate the flow tube (130) is connected to the flow tube (130); At least one pickup sensor (170L, 170R) configured to measure the movement of the flow tube (130) is connected to the flow tube (130); Connect the support rods (140, 140') to the flow tube (130); Connect the balance bar (150) to the struts (140, 140'); and The pattern separator (300) is connected to at least one of the flow tube (130) or the balance bar (150), the pattern separator (300) comprising: a mass portion (302); and A first connecting portion (304a) includes a first end connected to the mass portion (302), wherein the first connecting portion (304a) has a first stiffness in the driving direction (Y) and a second stiffness in an orthogonal direction (Z), the orthogonal direction (Z) being orthogonal to both the driving direction (Y) and the longitudinal direction of the balance bar (150), and the second stiffness being different from the first stiffness.

19. The method for assembling a Coriolis flow meter (100) according to claim 18, wherein, Connecting the balance bar (150) to the struts (140, 140') also includes: Connect the first balance bar (150) to the support rods (140, 140'); Connect the second balance bar (150') to the struts (140, 140'); and The first balance bar (150) is connected to the second balance bar (150') by using one or more brackets (160L, 160R, 161, 161').

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