TECHNICAL FIELD

The embodiments described below relate to vibratory sensors and, more particularly, to a flowmeter and related methods for reducing the deleterious effects of external magnetic fields.

BACKGROUND

Vibrating sensors, such as for example, vibrating densitometers and Coriolis flowmeters are generally known, and are used to measure mass flow and other information related to materials flowing through a conduit in the flowmeter. Exemplary Coriolis flowmeters are disclosed in U.S. Patent 4,109,524, U.S. Patent 4,491,025, and Re. 31,450. These flowmeters have meter assemblies with one or more conduits of a straight or curved configuration. Each conduit configuration in a Coriolis mass flowmeter, for example, has a set of natural vibration modes, which may be of simple bending, torsional, or coupled type. Each conduit can be driven to oscillate at a preferred mode. When there is no flow through the flowmeter, a driving force applied to the conduit(s) causes all points along the conduit(s) to oscillate with identical phase or with a small “zero offset”, which is a time delay measured at zero flow.

As material begins to flow through the conduit(s), Coriolis forces cause each point along the conduit(s) to have a different phase. For example, the phase at the inlet end of the flowmeter lags the phase at the centralized driver position, while the phase at the outlet leads the phase at the centralized driver position. Pickoffs on the conduit(s) produce sinusoidal signals representative of the motion of the conduit(s). Signals output from the pickoffs are processed to determine the time delay between the pickoffs, which is known as the AT. The time delay between the two or more pickoffs is proportional to the mass flow rate of material flowing through the conduit(s).

A meter electronics connected to the driver generates a drive signal to operate the driver and also to determine a mass flow rate and/or other properties of a process material from signals received from the pickoffs. The driver may comprise one of many well- known arrangements; however, a magnet and an opposing drive coil have received great success in the flowmeter industry. An alternating current is passed to the drive coil for vibrating the conduit(s) at a desired conduit amplitude and frequency. It is also known in the art to provide the pickoffs as a magnet and coil arrangement very similar to the driver arrangement.

When a strong external magnet is placed proximate a pickoff, a few effects are observable. First, the pickoff voltage will either rapidly drop or increase. Second, the phase shift between pickoffs will either rapidly drop or increase. Once the magnet is removed, the sensor voltages and phase shift return to normal. The flow rate reported by the meter can be altered by modifying the magnetic field proximate a transducer with an externally applied magnet. An incorrect flow rate reading caused by an external magnet could potentially be used to misrepresent the amount of a commodity that is flowing through the meter for financial benefit. What is needed is a device and method to reduce the negative effect of an externally applied magnet on the flow rate measurement precision.

SUMMARY

According to an embodiment, a flowmeter comprises flow conduits and transducers connected to the flow conduits, wherein the transducers comprise a driver and pick-off sensors. A meter electronics is configured to drive the driver to oscillate the flow conduits in a first bending mode, and to receive signals from the pick-off sensors. A magnetic shield is proximate at least one of the transducers, wherein the magnetic shield is configured to attenuate a strength of an external magnet’s flux effect on the transducer’s magnetic field.

According to an embodiment, a method for operating a flowmeter comprises flowing a flow material through flow conduits of the flowmeter and driving a driver connected to the flow conduits to oscillate the flow conduits in a first bending mode. Signals are received from pick-off sensors connected to the flow conduits. A magnetic shield is placed inside a case of the flowmeter proximate at least one of the driver and one or more pick-off sensors. A flux effect on at least one of the driver and one or more pickoff sensors by an external magnetic field proximate the flowmeter is attenuated with the magnetic shield.

According to an embodiment, a method for constructing a flowmeter comprises providing flow conduits configured to receive a fluid therein and connecting transducers to the flow conduits, wherein the transducers comprise at least one driver and pick-off sensors. The driver is driven with signals from a meter electronics to oscillate the flow conduits in a first bending mode, and signals are received by the meter electronics, from the pick-off sensors. A magnetic shield is installed proximate at least one of the transducers, wherein the magnetic shield is configured to attenuate a flux effect of an external magnet’s field on at least one of the transducers.

ASPECTS

A flowmeter comprises flow conduits and transducers connected to the flow conduits, wherein the transducers comprise a driver and pick-off sensors. A meter electronics is configured to drive the driver to oscillate the flow conduits in a first bending mode, and to receive signals from the pick-off sensors. A magnetic shield is proximate at least one of the transducers, wherein the magnetic shield is configured to attenuate a strength of an external magnet’ s flux effect on the transducer’ s magnetic field.

Preferably, the magnetic shield is mounted on a portion of the transducer.

Preferably, the magnetic shield is mounted on a portion of the flowmeter exclusive of the transducer.

Preferably, at least one transducer comprises mounting arms, wherein a coil portion and a magnet portion of the transducer are each coupled to the mounting arms, respectively, wherein the mounting arms are coupled to first and second flow conduits, respectively, and wherein the magnetic shield comprises a portion attached to at least one mounting arm.

Preferably, the magnetic shield comprises a first frustoconical portion in communication with a cylindrical portion, and a second frustoconical portion in communication with the cylindrical portion.

Preferably, an aperture that circumscribes a mounting arm is defined by at least one of the first frustoconical portion and the second frustoconical portion.

Preferably, the magnetic shield comprises one or more flat plates attached to at least one arm.

Preferably, the magnetic shield comprises a cup-shape defined by a cylindrical portion and a base portion.

Preferably, the magnetic shield comprises a faceted barrel portion. A method for operating a flowmeter comprises flowing a flow material through flow conduits of the flowmeter and driving a driver connected to the flow conduits to oscillate the flow conduits in a first bending mode. Signals are received from pick-off sensors connected to the flow conduits. A magnetic shield is placed inside a case of the flowmeter proximate at least one of the driver and one or more pick-off sensors. A flux effect on at least one of the driver and one or more pick-off sensors by an external magnetic field proximate the flowmeter is attenuated with the magnetic shield.

A method for constructing a flowmeter comprises providing flow conduits configured to receive a fluid therein and connecting transducers to the flow conduits, wherein the transducers comprise at least one driver and pick-off sensors. The driver is driven with signals from a meter electronics to oscillate the flow conduits in a first bending mode, and signals are received by the meter electronics, from the pick-off sensors. A magnetic shield is installed proximate at least one of the transducers, wherein the magnetic shield is configured to attenuate a flux effect of an external magnet’s field on at least one of the transducers.

Preferably, the method comprises the step of mounting the magnetic shield on a portion of the transducer.

Preferably, the method comprises the step of mounting the magnetic shield on a portion of the flowmeter exclusive of the transducer.

Preferably, the method comprises installing a mounting arm on a coil portion and installing a mounting arm on a magnet portion of the transducer, coupling the mounting arms to first and second flow conduits, respectively, and attaching a portion of the magnetic shield to at least one mounting arm.

Preferably, the method comprises the step of forming the magnetic shield with a first frustoconical portion in communication with a cylindrical portion, and a second frustoconical portion in communication with the cylindrical portion.

Preferably, the method comprises the step of circumscribing a mounting arm with an aperture defined by at least one of the first frustoconical portion and the second frustoconical portion.

Preferably, the magnetic shield comprises one or more flat plates attached to at least one arm. Preferably, the magnetic shield comprises a cup-shape defined by a cylindrical portion and a base portion.

Preferably, the magnetic shield comprises a faceted barrel portion.

Preferably, the magnetic shield comprises a domed or semi-spherical portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The same reference number represents the same element on all drawings. It should be understood that the drawings are not necessarily to scale.

FIG. 1 shows a vibratory meter according to an embodiment;

FIG. 2 shows a meter electronics according to an embodiment;

FIG. 3 illustrates the effect of magnetic fields on a flowmeter sensor pickoff voltage;

FIG. 4 illustrates the effect of magnetic fields on flow rate measurement;

FIG. 5 illustrates a cross-sectional view of a prior art transducer assembly;

FIG. 6 illustrates an axisymmetric cross-sectional view of a transducer assembly and the magnetic field associated therewith;

FIG. 7 illustrates how an external magnetic field can change the direction and strength of the magnetic field of the flowmeter transducer of FIG. 6;

FIGS. 8A-B illustrate an embodiment of a transducer having a magnetic shield;

FIGS. 9A-B illustrate another embodiment of a transducer having a magnetic shield;

FIGS. 10A-B illustrate yet another embodiment of a transducer having a magnetic shield;

FIGS. 11 A-B illustrate yet another embodiment of a transducer having a magnetic shield;

FIG. 12 illustrates a floating shield embodiment of a portion of a flowmeter assembly;

FIG. 13 illustrates a domed or semi- spherical embodiment of a magnetic shield; and

FIG. 14 illustrates another floating shield embodiment of a portion of a flowmeter assembly. DETAILED DESCRIPTION

FIGS. 1 - 14 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of embodiments of a flowmeter sensor assembly, drivers, and pickoff sensors. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the present description. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of embodiments. As a result, the embodiments described below are not limited to the specific examples described below, but only by the claims and their equivalents.

FIG. 1 shows a flowmeter 5 according to an embodiment. The flowmeter 5 comprises a sensor assembly 10 and meter electronics 20. The meter electronics 20 is connected to the sensor assembly 10 via leads 100 and is configured to provide measurements of one or more of a density, mass flow rate, volume flow rate, totalized mass flow, temperature, or other measurements or information over a communication path 26. The flowmeter 5 can comprise a Coriolis mass flowmeter or other vibratory flowmeter. It should be apparent to those skilled in the art that the flowmeter 5 can comprise any manner of flowmeter 5, regardless of the number of drivers, pick-off sensors, flow conduits, or the operating mode of vibration.

The sensor assembly 10 includes a pair of flanges 101 and 10T, manifolds 102 and 102', a driver 104, pick-off sensors 105 and 105', and flow conduits 103A and 103B. The driver 104 and the pick-off sensors 105 and 105' are connected to the flow conduits 103A and 103B.

The flanges 101 and 10T are affixed to the manifolds 102 and 102'. The manifolds 102 and 102' can be affixed to opposite ends of a spacer 106 in some embodiments. The spacer 106 maintains the spacing between the manifolds 102 and 102'. When the sensor assembly 10 is inserted into a pipeline (not shown) which carries the process fluid being measured, the process fluid enters the sensor assembly 10 through the flange 101, passes through the inlet manifold 102 where the total amount of process fluid is directed to enter the flow conduits 103A and 103B, flows through the flow conduits 103A and 103B and back into the outlet manifold 102', where it exits the sensor assembly 10 through the flange 101'. The process fluid can comprise a liquid. The process fluid can comprise a gas. The process fluid can comprise a multi-phase fluid, such as a liquid including entrained gases and/or entrained solids, for example without limitation. The flow conduits 103 A and 103B are selected and appropriately mounted to the inlet manifold 102 and to the outlet manifold 102' so as to have substantially the same mass distribution, moments of inertia, and elastic moduli about the bending axes W-W and W'-W', respectively. The flow conduits 103A and 103B extend outwardly from the manifolds 102 and 102' in an essentially parallel fashion.

The flow conduits 103A and 103B are driven by the driver 104 in opposite directions about the respective bending axes W and W' and at what is termed the first out of phase bending mode of the flowmeter 5. The driver 104 may comprise one of many well-known arrangements, such as a magnet mounted to the flow conduit 103 A and an opposing coil mounted to the flow conduit 103B. An alternating current is passed through the opposing coil to cause both conduits to oscillate. A suitable drive signal is applied by the meter electronics 20 to the driver 104 via lead 110. Other driver devices are contemplated and are within the scope of the description and claims.

The meter electronics 20 receives sensor signals on leads 111 and 111', respectively. The meter electronics 20 produces a drive signal on lead 110 which causes the driver 104 to oscillate the flow conduits 103A and 103B. Other sensor devices are contemplated and are within the scope of the description and claims.

The meter electronics 20 processes the left and right velocity signals from the pickoff sensors 105 and 105' in order to compute a flow rate, among other things. The communication path 26 provides an input and an output means that allows the meter electronics 20 to interface with an operator or with other electronic systems. The description of FIG. 1 is provided merely as an example of the operation of a flowmeter and is not intended to limit the teaching of the present invention. In embodiments, single tube and multi-tube flowmeters having one or more drivers and pickoffs are contemplated.

The meter electronics 20 in one embodiment is configured to vibrate the flow conduit 103A and 103B. The vibration is performed by the driver 104. The meter electronics 20 further receives resulting vibrational signals from the pickoff sensors 105 and 105'. The vibrational signals comprise a vibrational response of the flow conduits 103A and 103B. The meter electronics 20 processes the vibrational response and determines a response frequency and/or phase difference. The meter electronics 20 processes the vibrational response and determines one or more flow measurements, including a mass flow rate and/or density of the process fluid. Other vibrational response characteristics and/or flow measurements are contemplated and are within the scope of the description and claims.

In one embodiment, the flow conduits 103 A and 103B comprise substantially omega-shaped flow conduits, as shown. Alternatively, in other embodiments, the flowmeter can comprise substantially straight flow conduits, U-shaped conduits, deltashaped conduits, etc. Additional flowmeter shapes and/or configurations can be used and are within the scope of the description and claims. Embodiments where only a single flow conduit or more than two flow conduits are also contemplated.

FIG. 2 is a block diagram of the meter electronics 20 of a flowmeter 5 according to an embodiment. In operation, the flowmeter 5 provides various measurement values that may be outputted including one or more of a measured or averaged value of mass flow rate, volume flow rate, individual flow component mass and volume flow rates, and total flow rate, including, for example, both volume and mass flow.

The flowmeter 5 generates a vibrational response. The vibrational response is received and processed by the meter electronics 20 to generate one or more fluid measurement values. The values can be monitored, recorded, saved, totaled, and/or output.

The meter electronics 20 includes an interface 201, a processing system 203 in communication with the interface 201, and a storage system 204 in communication with the processing system 203. Although these components are shown as distinct blocks, it should be understood that the meter electronics 20 can be comprised of various combinations of integrated and/or discrete components.

The interface 201 is configured to communicate with the sensor assembly 10 of the flowmeter 5. The interface 201 may be configured to couple to the leads 100 (see FIG. 1) and exchange signals with the driver 104, pickoff sensors 105 and 105', and temperature sensors (not shown), for example. The interface 201 may be further configured to communicate over the communication path 26, such as to external devices.

The processing system 203 can comprise any manner of processing system. The processing system 203 is configured to retrieve and execute stored routines in order to operate the flowmeter 5. The storage system 204 can store routines including a flowmeter routine 205, a magnetic field detection routine 209, and an alternate bending mode routine 211. Other measurement/processing routines are contemplated and are within the scope of the description and claims. The storage system 204 can store measurements, received values, working values, and other information. In some embodiments, the storage system stores a mass flow (m ) 221, a density (p) 225, a viscosity (p) 223, a temperature (T) 224, a drive gain 306, a transducer voltage 303, and any other variables known in the art.

The flowmeter routine 205 can produce and store fluid quantifications and flow measurements. These values can comprise substantially instantaneous measurement values or can comprise totalized or accumulated values. For example, the flowmeter routine 205 can generate mass flow measurements and store them in the mass flow 221 storage of the storage system 204, for example. The flowmeter routine 205 can generate density 225 measurements and store them in the density 225 storage, for example. The mass flow 221 and density 225 values are determined from the vibrational response, as previously discussed and as known in the art. The mass flow and other measurements can comprise a substantially instantaneous value, can comprise a sample, can comprise an averaged value over a time interval, or can comprise an accumulated value over a time interval. The time interval may be chosen to correspond to a block of time during which certain fluid conditions are detected, for example a liquid-only fluid state, or alternatively, a fluid state including liquids and entrained gas. In addition, other mass flow and related quantifications are contemplated and are within the scope of the description and claims.

Turning to FIG. 3, it is shown that by monitoring meter electronics 20, external magnetic fields, whether from electromagnetic sources or permanent magnets, affect the reading of the sensor assembly 10 when magnets and coils are utilized for the pick-off sensors 105 and 105'. It is evident that relatively sharp and symmetrical step changes are present.

The region noted by Bracket #1 in FIG. 3 represents a magnet being placed proximate the pick-off sensor 105’ located closest to the flowmeter’s output. When a magnet is placed there, a relatively sharp and symmetrical step change in voltage is detected in the signal provided by the pick-off sensor 105’ located closest to the flowmeter’s output (labeled POourin FIG. 3). The region noted by Bracket #2 in FIG. 3 represents a magnet being placed proximate the pick-off sensor 105 located closest to the flowmeter’s input. When a magnet is placed there, a relatively sharp and symmetrical step change in voltage is also detected in the signal provided by the pick-off sensor 105’ located closest to the flowmeter’s output (labeled POour in FIG. 3). Voltage spikes are also detected in the signal provided by the pick-off sensor 105 located closest to the flowmeter’s input (labeled POiN in FIG. 3). Voltage spikes are also detected in the signal provided by the driver 104.

The region noted by Bracket #3 in FIG. 3 represents a magnet being placed proximate the driver 104. A detectable and relatively sharp and symmetrical step change in current is detected in the signal provided to the driver 104.

Turning to FIG. 4, it is shown that external magnets affect the AT readings of the flowmeter 5. When the driver 104 stimulates the flow conduits 103 A, 103B to oscillate in opposition at the natural resonant frequency, the flow conduits 103 A, 103B oscillate, and the voltage generated from each pick-off sensor 105, 105’ generates a sine wave. This indicates the motion of one conduit relative to the other. The time delay between the two sine waves is referred to as the AT, which is directly proportional to the mass flow rate. If the phase of either of the flow conduits 103A, 103B is affected, AT changes. Flow should cause a positive change in one pick-off sensor’s phase and an equal negative change in the other pick-off sensor’s phase.

The region noted by Bracket #1 in FIG. 4 represents a magnet being placed proximate the pick-off sensor 105’ located closest to the flowmeter’s output. When a magnet is placed there, a relatively sharp and symmetrical stepped decrease in AT is detected.

The region noted by Bracket #2 in FIG. 4 represents a magnet being placed proximate the pick-off sensor 105 located closest to the flowmeter’s input. When a magnet is placed there, a relatively sharp and symmetrical stepped increase in AT is detected.

The region noted by Bracket #3 in FIG. 4 represents a magnet being placed proximate the driver 104. When a magnet is placed there, a relatively sharp and symmetrical stepped decrease in AT is detected. FIG. 5 shows a cross-sectional view of a prior art transducer assembly 300. The transducer assembly 300 can be coupled to the first and second flow conduits 103A, 103B. The prior art transducer assembly 300 comprises a coil portion 304A and a magnet portion 304B. The magnet portion 204B comprises a magnet 311. The magnet 311 can be positioned within a magnet keeper 313 that can help direct the magnetic field, and is typically made from a magnetic steel. The magnet portion 304B may also comprise a pole piece 315. The magnet portion 304B comprises a typical magnet portion of prior art sensor components. The magnet portion 304B may be coupled to the second flow conduit 103B with a mounting bracket (not shown for clarity). The mounting bracket may be coupled to the flow conduit 103B according to well-known techniques such as welding, brazing, bonding, etc. The coil portion 304A may be coupled to the first flow conduit 103A with a mounting bracket (not shown for clarity). The mounting bracket may be coupled to the flow conduit 103A according to well-known techniques such as welding, brazing, bonding, etc. The coil portion 304A also comprises a coil bobbin 320. The coil bobbin 320 can include a magnet receiving portion 320’ for receiving at least a portion of the magnet 311. The coil bobbin 320 comprises a coil 322. The coil bobbin 320 can be held onto the mounting bracket 310 with a fastening device. Mounting arms 306 A, 306B are utilized to respectively connect the coil portion 304A and magnet portion 304B to first and second flow conduits 103A, 103B, respectively. For embodiments provided, transducer portions may be coupled to flow conduits 103A, 103B with mounting arms 306 A, 306B, as illustrated, but it will be understood that coupling may be accomplished using plates, brackets, mechanical structures, or by directly coupling transducer portions to flow conduits 103A, 103B without any intermediary structures. Direct coupling may include mechanically fastening, welding, brazing, adhering, or via any known coupling means in the art.

FIG. 6 illustrates an axisymmetric view of the magnetic field associated with a flowmeter transducer 104, 105, 105’, represented by lines of magnetic flux. The highest concentration of flux lines exists between the magnet and magnetic steel pickoff components. The pickoff assembly illustrated has a permanent magnet 311, a magnetic steel pole piece 315, and a magnetic steel magnet keeper 313. Dashed lines represent magnetic flux fields FIGS. 6, 7, 8B, 9B, 10B, 11B, 12, and 13. FIG. 7 illustrates how an external magnetic field can change the direction and strength of the flowmeter transducer 104, 105, 105’ magnetic field. The addition of flux from an external magnet 400 changes the magnitude of the magnetic field in the pickoff. This can be visualized by the flux lines interacting with the pickoff magnet 311. The Coriolis measurement precision is affected because the time difference measured by the Coriolis sensor electronics changes when the pickoff magnetic field changes.

FIGS. 8A and 8B illustrates an embodiment of the present invention, wherein the flowmeter transducer 104, 105, 105’ comprises a magnetic shield 500A proximate the coil portion 304A. The magnetic shield 500A is made from a magnetic steel, such as 1018 carbon steel, for example and without limitation. The magnetic shield 500A guides the external magnet’s flux lines away from the sensing components of the transducer 104, 105, 105’. The effect of the external magnet on the Coriolis sensor measurement is reduced because less of the external magnet flux interferes with the magnetic field inherent to the transducer 104, 105, 105’. The redirection of the flux lines generated by the external magnetic field is achieved because the permeability of the steel is ~ 100 times greater than air. Effectively, the magnetic fields from the external magnet are far more prone to travel inside the magnetic steel instead of through the air. Therefore, the magnetic shield 500A provides a path for the magnetic field that promotes the fields to largely bypass the coil 322 and magnet 311 of the transducer 104, 105, 105’and return back to the external magnet 400. This is illustrated in FIG. 8B.

The magnetic shield 500A can be cylindrical, curved, asymmetric, wavy, angled, bent, or with any geometry that helps redirect flux from an external magnetic field. The magnetic shield 500A can partially enclose, fully enclose, or not enclose the transducer 104, 105, 105’ at all, as long as it provides a reduction of the external magnetic flux. The magnetic shield 500A, in some embodiments is part of the transducer 104, 105, 105’ assembly. Some embodiments of the magnetic shield presented herein, are attached to the flowmeter sensor assembly 10. This may include portions of the flowmeter such as a flow conduit 103A, 103B, manifolds 102, 102’, a spacer 106, one or more brace bars 120, 120’, and/or a flowmeter case (not shown). The magnetic shield is placed within the internal space defined by the flowmeter case.

The magnetic shield 500A illustrated in FIG. 8 comprises a substantially cylindrical portion 501. A first frustoconical portion 503 and a second frustoconical portion 505. The second frustoconical portion 505 terminates to define an aperture 507 that circumscribes a mounting arm 306B. The first frustoconical portion 503 is attached to mounting arm 306A. It should be noted that this may be reversed, and the second frustoconical portion 505 may terminate to define an opening 507 that circumscribes the mounting arm 306A, with the first frustoconical portion 503 being attached to mounting arm 306B. In an alternative embodiment, neither arm 306A, 306B is attached to magnetic shield 500 A, and instead the magnetic shield 500 A is attached to another portion of the flowmeter 10.

A “flat plate” magnetic shield 500B, by itself, provides benefit to the transducer 104, 105, 105’ depending on the orientation and location of the external magnet relative to the transducer 104, 105, 105’, as illustrated in FIGS. 9A and 9B. The flat magnetic shield 500B is positioned between 20mm and 75mm from the pole piece 315. In another embodiment, the flat magnetic shield 500B is positioned between 40mm and 50mm from the pole piece 315. The particular distance depends on flowmeter materials, flowmeter geometry, magnet strength, case material and geometry, etc. FIG. 9B illustrates that the magnetic shield 500B attenuates an external magnet’s field, thus conferring only a minimal effect on the transducer’s 104, 105, 105’ magnetic field. It is illustrated that the magnetic shield 500B is attached to arm 306A. It will be understood that this style of magnetic shield 500B may be attached to arm 306B. In yet another embodiment, each arm 306A, and 306B may comprise a magnetic shield 500B. It will be understood that this style of magnetic shield 500B may be formed integrally with either arm 306A or 306B. The magnetic shield 500B may be a round plate, a square plate, a triangular plate, a polygonal plate, an ovoid plate, an irregularly- shaped plate, or any other shape known in the art. A round plate embodiment is illustrated in FIG. 9A. More than one plate may be mounted on an arm 306 A, 306B.

A “cup shaped” magnetic shield 500C, is also provided in an embodiment, as illustrated in FIGS. 10A and 10B. The cup magnetic shield 500C is illustrated as comprising a two-part assembly — namely a cylindrical portion 501 and a base portion 512. It will be understood that this assembly may be made from a single piece of material. It will be understood that this style of magnetic shield 500C may be attached to either arm 306 A or 306B. It will be understood that this style of magnetic shield 500C may be formed integrally with either arm 306A or 306B. FIG. 10B illustrates that the magnetic shield 500C attenuates an external magnet’s field, thus conferring only a minimal effect on the transducer’s 104, 105, 105’ magnetic field.

A “faceted” magnetic shield 500D, is also provided in an embodiment, as illustrated in FIGS. 11A and 11B. The faceted magnetic shield 500D comprises a base 520 and a faceted barrel portion 522 attached to the base 520. The faceted magnetic shield 500D is illustrated as comprising a one-part assembly, but can be constructed from multiple parts. It will be understood that this style of magnetic shield 500D may be attached to either arm 306A or 306B. It will be understood that this style of magnetic shield 500D may be formed integrally with either arm 306A or 306B. FIG. 1 IB illustrates that the magnetic shield 500D attenuates an external magnet’s field, thus conferring only a minimal effect on the transducer’ s 104, 105, 105’ magnetic field. A frustoconical region 524 defines an aperture 526 that circumscribes a mounting arm 306B. It is illustrated that the magnetic shield 500D is attached to arm 306A. It will be understood that this style of magnetic shield 500D may be attached to arm 306B.

FIGS. 12-14 are provided as examples of cross sections of “floating shield” embodiments 500E-500G. FIGS. 12-14 illustrate that the magnetic shields 500E, 500F, 500G each attenuate an external magnet’s field, thus conferring only a minimal effect on the transducer’s 104, 105, 105’ magnetic field. Note that any of the magnetic shield shapes/orientations described herein may be adapted to float. Floating embodiments are shields that do not attach directly to the transducer 104, 105, 105’ or related mounting arms 306A, 306B. Furthermore, the embodiment of FIG. 13 may be adapted to attach directly to the transducer 104, 105, 105’ or related mounting arms 306 A, 306B or a mounting plate/bracket associated with a transducer or flow tube 103 A, 103B.

In floating embodiments, the magnetic shields are mounted to the flowmeter case, brace bars 120, 120’, flow tubes 103A, 103B, spacer 106, or any other portion of the flowmeter 10. In embodiments where the magnetic shields are mounted to the flowmeter case, they are mounted directly to the case, or alternatively, via a connecting member. The connecting member may be ferrous, non-ferrous, or comprise multiple portions such that some portions are ferrous and some portions are non-ferrous.

The embodiment of FIG. 13 comprises a domed or semi- spherical magnetic shield 500F. This embodiment of a magnetic shield 500F comprises an internal radius 530 and external radius 532. The internal radius 530 may comprise a constant radius or a variable radius. The external radius 532 may comprise a constant radius or a variable radius. The internal radius 530 may be the same as the external radius 532. The internal radius 530 may differ from the external radius 532.

The magnetic shields 500A-500F may be constructed having a relatively small or relatively large mass. For example, a 50mm tall vertical cylindrical shield as illustrated in FIGS. 10 A, 10B can reduce the external flux effect by 73% when constructed of material that is approximately 1.6mm thick, 74% when approximately 3.2mm thick., and 77% when approximately 12.7mm thick. The 12.7mm thick shield offers a 4% flux reduction advantage over the 3.2mm shield but is over two times as heavy. The small relative mass of the 3.2mm shield is generally considered to be more beneficial because it minimizes the effect on Coriolis meter performance while maintaining a similar level of flux reduction to the 12.7mm shield. However, in floating embodiments, the relative mass may have lesser effects on meter performance, and may thus be preferred.

The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the present description. Indeed, persons skilled in the art will recognize that certain elements of the above-described embodiments may variously be combined or eliminated to create further embodiments, and such further embodiments fall within the scope and teachings of the present description. It will also be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the present description.

Thus, although specific embodiments are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present description, as those skilled in the relevant art will recognize. The teachings provided herein can be applied to other sensors, sensor brackets, and conduits and not just to the embodiments described above and shown in the accompanying figures. Accordingly, the scope of the embodiments described above should be determined from the following claims.