transducer

Abstract

A transducer for a mass flow meter, where the mass flow meter is arranged inside an outer tube working as a pressure containing part for the mass flow meter. The mass flow meter has a tubular housing. At least one flexible plate able to vibrate in 5 torsion, the flexible plate provided with a magnetic or magnetizable material. An electrically conducting material is embedded in the tubular housing or embedded in the outer tube. The electrically conducting material provides a main current path of the transducer, wherein current in the main current path inducing at least one torque in the flexible plate via the magnetic or magnetizable material. 10 Vibrations of the flexible plate induce current in the main current path via the magnetic or magnetizable material, the transducer functioning as a pick-up for the mass flow meter. 2 15

Description

[0001] TRANSDUCER

[0002] BACKGROUND

[0003] The invention relates to a transducer. The transducer may be used for sensors arranged inside a high-pressure pipeline. The transducer may be used as an electromagnetic actuator or pick-up for a sensor with a tubular housing arranged inside the high-pressure pipeline. The sensor may be a mass flow meter.

[0004] INTRODUCTION

[0005] Fluids such as liquid CO2 for carbon dioxide capture and storage (CCS), fluid petroleum products, natural gas, hydrogen and water are often transported in pipelines. Such fluids are often transported under high pressure. The pipelines may be subsea on large depths, but also on land. Fluids may also be transported through pipelines in land facilities such as oil refineries or other processing facilities. The fluids are transported in pipelines with large dimensions and the fluids typically may have low density. Liquid H2 has e.g. low density while H2 in gas form has extremely low density. A high-density fluid such as e.g. liquid CO2, and natural gas, are often transported / stored subsea at high depths and at a water temperature of 4°C or in long pipelines with cooling arrangements. Liquid CCte may not be transported at atmospheric pressure or at environmental temperatures above 4°C as this would require a too high pressure to enable transport in a pipeline for practical reasons (thickness of pipeline etc). At 4°C on the ocean floor the pressure would be about 90 bar. Building a pipeline for transport of liquid CO2 at the ocean floor would therefore be possible and practical. Liquid CO2 has a mass density of about 1 ,1 tons per cubic meter. Liquid H2 has a mass density of about 70kg per cubic meter. The fluid transport may be monitored in real-time by measuring the amount of fluid moving through the pipeline. Mass flow measurements may be preferred over volume flow, as mass do not vary with changes in pressure or temperature. Mass flow measurements may thus be more accurate. Mass flow meters based on ultrasound measurements may also not be applicable for use with liquids such as e.g. liquid CO2, as the ultrasound waves are attenuated by the liquid. Mass flow meters using traditional Coriolis technology can operate by vibrating a pipe carrying a flowing fluid between an inlet and an outlet. This vibration of the pipe provides an oscillation, a variation of a measure of the pipe (e.g. position) about a central value. The inertia of the flowing fluid resists the vibration motion and causes the pipe to twist. This twist results in a time lag (phase shift) of oscillations of the pipe between the inlet side and the outlet side and this phase shift is directly affected by the mass of the fluid passing through the pipe. Traditional Coriolis flow meters divide the fluid flow in two pipes in order to provide net zero force from the drive.

[0006] Traditional Coriolis direct mass flow measurement may be unsuitable for measurements of mass flow for high pressure fluids, in particular for low density fluids d. Indirect mass flow measurements of high pressure fluids may be performed by use of differential pressure and / or density of the fluid, but may be inaccurate.

[0007] E.g. hydrogen and CO2 transport pipes have very large dimensions (diameter up to 24 or 30 inches) and the pressure is typically 100-200 bars. Presently existing Coriolis mass flow meters have a maximum diameter of 16 inches and may not be used for measuring mass flow of fluid in such large pipes. For transport of fluids at very high pressures e.g. 300 bars, the largest usable traditional Coriolis meter may be only 6-7 inches and with a large thickness to withstand the pressure. For measurement of fluids with low density a Coriolis flowmeter must have thin tubular walls to be able to detect the mass flow. Thin tubular walls cannot withstand high pressure. Existing Coriolis mass flow meters may therefore not be used in high pressure applications e.g. fluid at a pressure above 100 bars, if the line size are not very small. Existing Coriolis mass flow meters would have to be made with a large thickness to be able to withstand these high pressures that would result in a too stiff construction that are unable to vibrate for detection of mass flow. For high operation pressures and / or large diameter pipelines, the pressure carrying metal pipe for the Coriolis flow meter would be thick. Applying a force to the measuring pipe by use of electromagnetic actuators would then not be possible for such a thick pipeline. Traditional Coriolis flow meters may also not be able to measure the mass flow of low density fluids, as this would require a high speed of the fluid flow to provide a signal and such a high speed would not be possible. The design of the traditional Coriolis flow meter with reduced diameter tubes as compared with the pipe for the fluid flow may also result in a pressure drop over the mass flow meter due to a venturi effect. For Fhthe pressure drop over the traditional Coriolis mass flow meter may e.g. be 50-100 bars. The pressure drop may result in boiling of e.g. the fluid e.g. liquid CO2 , providing bubbles in the fluid flow resulting in a poor measurement by the mass flow meter.

[0008] US5,392,656 discloses a mass flowmeter with a nonvibrating conduit providing a flow passage divided into two parallel and equal subpassages by a planar member with the leading and trailing edges secured to the wall of the flow passage. The planar member is torsionally vibrated about the central axis thereof substantially coinciding with the center line of the flow passage. Two actuators are arranged on the inside of the conduit facing each other. The actuators may extend into the wall of the conduit or through the wall to be close to the planar member. A pair of vibration sensors detect the torsional vibration of the planar member respectively at two different cross sections of the flow passage. The mass flow rate of media moving through the flow passage is determined as a function of a phase angle difference between two alternating electrical signals respectively provided by the pair of vibration sensors. The arrangement of the actuators close to the planar member provides a limited vibratory torque to the planar member.

[0009] In prior art solutions where electric conductors are wound around the outer tube, there will be a need for several thousand windings to provide a magnetic field inside the outer tube sufficient to actuate the flexible plate or for detecting the movements of the flexible plate.

[0010] For a thick pressure housing, use of prior art electromagnetic actuators would not be possible. Prior art electromagnetic actuators also have problems with eddy currents in the outer pressure housing resulting in dissipation of energy and reduced efficiency.

[0011] There is a need for improved actuators and pick-ups which also may be used for high-pressure measurements of high-pressure fluids inside a pipe system. SUMMARY OF THE INVENTION

[0012] An improved transducer is provided. The transducer is adapted for a tube-in tubesystem. The transducer may be used as an electromagnetic actuator and / or a pick-up for a sensor arranged inside an outer tube, e.g. a mass flow meter for measuring a fluid flow inside a pipeline. The transducer may be used for high- pressure measurements of high-pressure fluids inside a pipe system.

[0013] In a first aspect, the invention provides a transducer for a mass flow meter, where the mass flow meter is arranged inside an outer tube working as a pressure containing part for the mass flow meter, the mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, the flexible plate provided with a magnetic or magnetizable material. The transducer comprising an electrically conducting material embedded in the tubular housing or embedded in the outer tube, the electrically conducting material providing a main current path of the transducer, wherein current in the main current path inducing at least one torque in the flexible plate via the magnetic or magnetizable material.

[0014] In a second aspect, the invention provides a transducer for a mass flow meter, where the mass flow meter is arranged inside an outer tube working as a pressure containing part for the mass flow meter, the mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, the flexible plate provided with a magnetic or magnetizable material in predetermined positions. The the transducer comprising an electrically conducting material embedded in the tubular housing or embedded in the outer tube, the electrically conducting material providing a main current path of the transducer, wherein vibrations of the flexible plate inducing current in the main current path via the magnetic or magnetizable material, the transducer functioning as a pick-up for the mass flow meter.

[0015] The ratio between the specific conductance of the electrically conducting material embedded in the tubular housing or embedded in the outer tube and the material of the outer tube may be at least 8:1 , preferably 10:1 or most preferably 20:1 . The ratio between the specific conductance of the electrically conducting material embedded in the tubular housing or embedded in the outer tube and the material of the tubular housing may be at least 8: 1 , preferably 10: 1 or most preferably 20: 1 .

[0016] The magnetic or magnetizable material may be permanent magnets.

[0017] The current in the main current path may be an oscillating current inducing an oscillating torque in the flexible plate. The transducer may include at least one electrical conductor on the outside of the outer tube. The current in the main current path may be induced by an external coil. At least one pair of electrical conductors may be arranged on the outside of the outer tube.

[0018] The transducer may further comprise at least one electrically conducting winding arranged on the outside of the outer tube.

[0019] The main current path of the transducer may further comprise at least one primary electrically conducting winding arranged on the outside of the outer tube, wherein the at least one primary winding passing through a core of a secondary coil arranged on the outside of the outer tube, wherein the core is preferably an iron core.

[0020] The main current path may further comprise a secondary electrically conducting winding arranged on the outside of the outer tube. The at least one winding and the secondary winding may be wound around a common core. A primary coil may be arranged on an outside of the outer tube. The primary coil may comprise a core, wherein the core is preferably an iron core. The main current path may further comprise a secondary electrically conducting winding arranged on the outside of the outer tube, the secondary winding passing through a common core of a primary coil. The secondary winding may be a single conductor, preferably an uninsulated conductor.

[0021] The primary coil and the secondary electrically conducting winding may be wound around a common core. The outer tube may be provided with holes or with throughgoing openings in areas of the main current path.

[0022] The outer tube may be made of a metal of low conductivity. The outer tube may be made of a magnetic material, a soft magnetic material, magnetic steel, carbon steel or nickel alloys. The electrically conducting material may be made of at least one of Cu, Ag, Au or Al (copper, silver, gold or aluminum). The primary electrically conducting winding may be made of at least one of Cu, Ag, Au or Al. The secondary electrically conducting winding may be made of at least one of Cu, Ag, Au or Al. The tubular housing may be made of a non-magnetic material. The tubular housing may be made of a non-magnetic metal. Areas of magnetic material may be embedded in the tubular housing.

[0023] The tubular housing and the outer tube may be bonded together by direct fusion, soldering, welding, diffusion welding or bracing. The tubular housing and the electrically conducting material embedded in the tubular housing may be bonded together by direct fusion, soldering, welding, diffusion welding or bracing. The outer tube and the electrically conducting material embedded in the outer tube may be bonded together by direct fusion, soldering, welding, diffusion welding or bracing.

[0024] In a further aspect, the invention provides a mass flow meter comprising at least one transducer as disclosed above.

[0025] The transducer may be used as an electromagnetic actuator for a sensor arranged inside an outer tube. The transducer may be used as a pickup for a sensor arranged inside an outer tube. The transducer may be used in a sensor for measuring mass flow of fluid of CO2 , NH3 , H2 or natural gas. The transducer may be used in a sensor for high-pressure measurements of high-pressure fluids inside a pipe system.

[0026] The present invention enables use of a strong outer tube which is required for high pressure applications. High pressure applications may be pressures above e.g. 100 bar and up to several thousand bar. The thickness of the wall of the outer tube is important in high pressure application. The use of a an electrically conducting material embedded on the inside of the outer tube and an electrical conductor on the outside of the outer tube enable providing a magnetic field on the inside of the outer tube even in high pressure applications where a thick outer tube is required for withstanding the high pressure. The transducer enables use of even stronger outer pipes and use also in very high fluid pressure pipelines. The pressure may in some pipelines be as high as several thousand bar.

[0027] The transducer construction and use of less expensive materials as e.g. ferritic material, magnetic steel and carbon steel provides a cost effective solution. The production of the transducer may also be efficient and cost effective.

[0028] BRIEF DESCRIPTION OF DRAWINGS

[0029] Example embodiments will now be described with reference to the drawings. The example embodiments are examples only and not limiting for the disclosure.

[0030] Figure 1 A is a perspective view illustrating an exemplary embodiment of a mass flow meter including a tubular housing and a flexible plate positioned within the tubular housing and where the mass flow meter is provided with two actuating devices arranged about a longitudinal center of the flexible plate and two sensors arranged about a longitudinal center of the flexible plate, and with the flexible plate illustrated in an actuated state.

[0031] Figure 1 B is a perspective view illustrating an exemplary embodiment of a mass flow meter including a tubular housing and a flexible plate positioned within the tubular housing and where the mass flow meter is provided with two actuating devices arranged about a longitudinal center of the flexible plate and two sensors arranged about a longitudinal center of the flexible plate, and with the flexible plate illustrated in an unactuated state and where the flexible plate is provided with groups of magnets or magnetizable material.

[0032] Figure 1 C is a perspective view illustrating an exemplary embodiment of a mass flow meter including a tubular housing and a flexible plate positioned within the tubular housing and provided with an actuating device arranged in an area about a longitudinal center of the flexible plate, and with the flexible plate illustrated in an unactuated state and with two groups of permanent magnets or magnetizable material forming a dipole, are arranged on the flexible plate. Figure 2 illustrates in perspective view an exemplary embodiment of a sensor 100 with a tubular housing 102 arranged inside an outer tube 101. The outer tuber working as a pressure containing part for the sensor. The sensor is provided with a flexible plate 103 arranged within the tubular housing 102. The flexible plate is provided with a magnetic or magnetizable material 104. The sensor is provided with two transducers 120. The two transducers are arranged on opposite sides of the sensor. The two transducers have the same construction. Each transducer includes two electrical conductors 109 arranged on the outside of the outer tube. The two electrical conductors 109 form a pair. The pair of electrical conductors may be connected to a power supply forming a circuit. The pair of electrical conductors may form a circuit and current induced in the circuit. The transducers in Fig.2 include an electrically conducting material 105 embedded in the tubular housing 102. The electrically conducting material may however in an alternatively exemplary embodiment be embedded in the outer tube as shown in Fig.4. The electrical conductors may be connected to the surface of the outer tube. The electrical conductors may alternatively be connected directly to the embedded electrically conducting material 105. The sensor may be a mass flow meter.

[0033] Figure 3 is a cross-sectional view along a longitudinal direction illustrating an exemplary embodiment of a sensor 100. The sensor 100 has a tubular housing 102 arranged inside an outer tube 101 . The outer tube working as a pressure containing part for the sensor. The sensor is provided with a flexible plate 103 arranged within the tubular housing 102. The flexible plate is provided with a magnetic or magnetizable material 107. The sensor is provided with two transducers 120. The two transducers are arranged on opposite sides of the sensor. The two transducers have the same construction. The transducers include an electrically conducting material 105 embedded in the tubular housing 102. The transducer includes an electrical conductor 110 arranged on the outside of the outer tube. The transducer has an external coil on the outside of the outer tube 101.

[0034] Figure 4 is a cross-sectional view along a longitudinal direction illustrating an exemplary embodiment of the sensor 100 from Figure 3. The sensor is provided with two transducers. Each of the transducers includes an electrically conducting material 106 embedded in the outer tube 101 instead of in the tubular housing as in Figure 3. The sensor may be a mass flow meter.

[0035] Figure 5 illustrates in longitudinal cross-section an exemplary embodiment of a sensor 100 with a tubular housing arranged on the inside of an outer tube 101 working as a pressure containing part for the sensor. The sensor is provided with at least one flexible plate 103 arranged within a tubular housing 102. The flexible plate is provided with a magnetic or magnetizable material 107. The flexible plate has four vanes. The magnetic or magnetizable material are arranged on each vane. The sensor is provided with four transducers 120. The transducers have the same construction. The transducers are arranged in pairs opposite of each other around the sensor 100 in the same longitudinal position on the sensor 100. Each of the transducers includes an electrically conducting material 105 embedded in the tubular housing 102. The sensor may be a mass flow meter. Each of the transducers has an external coil. The external coil is an electrical conductor on the outside of the outer tube.

[0036] Figure 6 is a cross-sectional view along a longitudinal direction illustrating an exemplary embodiment of a sensor 100 with a tubular housing 102 arranged on the inside of an outer tube 101 . The outer tuber working as a pressure containing part for the sensor. The sensor is provided with at least one flexible plate 103 arranged within the tubular housing 102. The flexible plate is provided with a magnetizable material 107. The sensor is provided with two transducers. Each of the transducers includes an electrically conducting material 105 embedded in the tubular housing 102. In the exemplary embodiment in Figure 6, the outer tube is provided with holes or through-going openings 115 for the electrical conductors 109. In Figure 6, the electrical conductors 109 extend through the outer housing 102 through the holes or through-going openings 115. The electrical conductors 109 are in direct contact with the embedded electrically conducting material 105. The electrically conducting material 105 has a reduced thickness in the areas contacting the electrical conductors 109. Each transducer includes two electrical conductors 109 arranged on the outside of the outer tube. The two electrical conductors 109 form a pair. The pair of electrical conductors may be connected to a power supply forming an electrical circuit with the embedded electrically conducting material. The pair of electrical conductors may form a circuit with the embedded electrically conducting material and current induced in the circuit. The sensor may be a mass flow meter.

[0037] Figure 7 illustrates in longitudinal cross-section an exemplary embodiment of the sensor 100 from Figure 5 with a tubular housing arranged on the inside of an outer tube 101 working as a pressure containing part for the sensor. In Figure 5, a magnetic material 116 is embedded in the tubular housing in addition to the electrically conducting material 105. The sensor is provided with at least one flexible plate 103 arranged within a tubular housing 102. The flexible plate is provided with a magnetizable material 107. Four transducers are provided for the sensor. Each of the transducers includes an electrically conducting material 105 and a magnetic material 116 embedded in the tubular housing 102. The sensor may be a mass flow meter. Each of the transducers has an external coil. The external coil is an electrical conductor on the outside of the outer tube.

[0038] Figure 8 illustrates in perspective view an exemplary embodiment of a sensor 100 with a tubular housing 102. The sensor is provided with a transducer. The transducer includes an electrically conducting material 105 embedded in the tubular housing 102. The transducer also includes a magnetic material 116 embedded in the tubular housing 102. An outer tube 101 is provided as a reinforcement for the sensor in the area of the transducer. The transducer includes two electrical conductors 109 on the outside of the outer tube. The electrical conductors 109 are connected to the outside of the outer tube.

[0039] Figure 9 is a cross-sectional view along a longitudinal direction illustrating an exemplary embodiment of a sensor 100 with a tubular housing 102 arranged on the inside of an outer tube 101 . The outer tuber working as a pressure containing part for the sensor. The sensor is provided with at least one flexible plate 103 arranged within the tubular housing 102. The flexible plate is provided with a magnetizable material 107. The sensor is provided with two transducers. Each transducer includes an electrically conducting material 105 embedded in the tubular housing 102. Each transducer includes two electrical conductors 109 electrically connected to the embedded electrically conducting material 105. The two electrical conductors extend through the outer tube to the outside of the outer tube. The sensor may be a mass flow meter.

[0040] Figure 10 illustrates an exemplary embodiment of the transducer from Figure 3 where each transducer includes an electrically conducting material 105 embedded in the tubular housing 102. Winding 110 is arranged on the outside of the outer tube and passes through the outer tube 101 and contacting the electrically conducting material 105.

[0041] Figure 11 illustrates an exemplary embodiment of the transducer from Figure 6 where the electrically conducting material 105 embedded in the tubular housing 102 has a reduced thickness in the areas contacting winding 109 arranged on the outside of the outer tube and passing through the outer tube 101 .

[0042] Figure 12A illustrates an exemplary embodiment of a sensor 100 with a tubular housing arranged inside an outer tube. The outer tube working as a pressure containing part for the sensor. The sensor is provided with a flexible plate 200 arranged within the tubular housing. The sensor is provided with three groups 201 , 202, 203 of transducers arranged along the length of the outer tube. Each group has four transducers arranged in different positions around the outer tube. The sensor may be a mass flow meter.

[0043] Figure 12B is a cross-sectional view along a longitudinal direction illustrating an exemplary embodiment of the sensor 100 from Figure 12A. Only the vertical vanes of the flexible plate are shown.

[0044] Figure 13 is an exemplary embodiment of the sensor in Figure 8 where the transducer comprising a winding arranged on the outside of the outer tube. The winding is an electrical conductor.

[0045] Figure 14 is a cross-sectional view along the line C-C from Figure 3, showing a shape of the electrical conducting material 500 embedded in the tubular housing. The drawings are illustrations and are not necessarily to scale. The drawings are intended to illustrate example embodiments of the subject matter disclosed herein and should therefore not be considered as limiting the scope of the disclosure.

[0046] DETAILED DESCRIPTION

[0047] Example embodiments are disclosed with reference to the drawings. The drawings are not necessarily to scale. The drawings are illustrations for understanding of the principles of the disclosed transducer e.g. the construction, function, manufacture and use of the transducer and its different parts. The transducer is exemplified for a sensor in the form of a mass flow meter in the drawings, but this is not to be considered limiting for the disclosure. The transducer may be used in other sensor systems comprising a tube inside an outer tube.

[0048] US10393560B2, which is hereby incorporated by reference in its entirety, discloses a mass flow meter 200 with a tubular housing 202, a flexible plate 204, an actuator 210, and at least two sensors 214 (214a, 214b, 214c, 214d), 216 (216a, 216b, 216c, 216c, 216d) as illustrated in Fig.1. The tubular housing 202 may be in the form of a generally circular cylinder having av length L, a wall thickness T and an inner radius R defining av cavity 206. The tubular housing has an inlet 202i for a fluid flow 102, and an outlet 202o for the fluid flow 102. The flexible plate has a width W. The flexible plate 204 can be coupled to an interior wall of the tubular housing such that the flexible plate can vibrate in torsion. The actuator 210 can be configured to apply an oscillating torque to the flexible plate sufficient to vibrate the flexible plate in torsion. The at least two sensors 214, 216 can each be configured to measure oscillations of the flexible plate as a function of time at different locations.

[0049] In exemplary embodiments, the actuator can be an electromagnetic actuator and at least a portion of the flexible plate can be made of a magnetic material. E.g. one or more permanent magnets may be embedded in the flexible plate. Use of permanent magnets require the actuator to be movable relative to the flexible plate to apply an oscillating torque to the flexible plate.

[0050] The mass flow meter can also include a computing device 212 in electrical communication with the at least two sensors and configured to determine a mass flow of fluid passing through the tubular housing from a phase shift between oscillations of the flexible plate measured by the at least two sensors.

[0051] As high-pressure fluids are often transported in thick-walled pipes that can be difficult to vibrate with sufficient strength for mass flow meters, the mass flow meter disclosed in US10393560B2 is provided with a tubular housing containing a flexible plate that vibrates in a twisting manner (torsion). The vibration of the plate is altered by the fluid flow therethrough. By measuring oscillations of the flexible plate at different locations, a phase lag of the plate oscillations can be measured and related to mass flow of a fluid traveling through the tubular housing, regardless of its thickness.

[0052] A mass flow meter with a tubular housing is shown in Fig.1A-1 C and disclosed in NO20220264, hereby incorporated by reference, with the same applicant as the present invention. The tubular housing contains a flexible plate that vibrates in a twisting manner (torsion). The vibration of the plate is altered by the fluid flow therethrough. By measuring oscillations of the flexible plate at different locations, a phase lag of the plate oscillations can be measured and related to mass flow of a fluid traveling through the tubular housing, regardless of its thickness. At least one electromagnetic actuator system is configured to apply at least two oscillating torques to the flexible plate sufficient to vibrate the flexible plate in torsion. At least two sensor systems are configured to measure oscillations of the flexible plate as a function of time at locations arising from the at least two applied oscillating torques. Fig. 1A and 1 B illustrate exemplary embodiments of the mass flow meter 310 with a tubular housing 350 from NO20220264. The tubular housing may be in the form of a generally circular cylinder having a length L, a wall thickness T, and an inner radius R defining a cavity 353. The length L of the tubular housing 300 and the cavity 353 extend along a longitudinal axis A between a housing inlet and a housing outlet positioned at ends of the tubular housing 350. The electromagnetic actuator systems 302, 303 may include an electromagnetic device arranged on the outside of the tubular housing and a magnetizable material arranged on the inside of the tubular housing. The two forces from the actuator systems are indicated as FAI , - FAI and FA2, - FA2 respectively. These force couples are the same as the torques. The resulting Coriolis forces -Fc, Fc acting on the flexible plate provides a torsional vibration with an angular velocity Qyand Qy. A net sum of the two oscillating torques applied to the flexible plate may be zero or substantially zero. The at least two oscillating torques may have opposite directions as illustrated in Fig.1 A. A sum of the at least two oscillating torques may be less than the largest of the at least two oscillating torques. If e.g. applying three oscillating torques the sum of all the oscillating torques should be zero or substantially zero. The mass flow meter is provided with two sensor systems (301 , 304).

[0053] FIG. 1A illustrates the flexible plate 352 positioned within the tubular housing. The flexible plate is illustrated in a 2ndharmonic oscillation. The tubular housing forming a cavity 353. The flexible plate 352 can extend in the direction of the longitudinal axis A of the tubular housing 350. The flexible plate 352 may extend along at least a part of the tubular housing 350. The flexible plate can be at least partially coupled to an interior wall of the tubular housing 350 (e.g., a wall of the cavity 353) at one or more locations. The flexible plate may be partially coupled to an interior wall of the tubular housing at opposed longitudinal ends of the flexible plate. As an example, a first terminal end of the flexible plate can be at least partially coupled to the tubular housing at or near the housing inlet i and a second terminal end of the flexible plate can be at least partially coupled to the tubular housing at or near the housing outlet. The flexible plate may alternatively be mounted to the tubular housing 350 at one of the terminal ends of the flexible plate. In further embodiments, more than one flexible plate 352 can be positioned within the housing (not shown).

[0054] As illustrated in FIG. 1 B, the flexible plate 352 can be in the form of a substantially planar plate. The flexible plate may have a width W approximately equal to an inner diameter (2R) of the tubular housing 350.

[0055] The mass flow meter can include an actuator system 302, 303. The actuator system may be configured to apply at least two oscillating torques to the flexible plate sufficient to vibrate the flexible plate in torsion. The actuator system 302, 303 may be arranged in different positions in the longitudinal direction of the tubular housing. The actuators may be positioned symmetrically about a longitudinal centre of the flexible plate 352.

[0056] The actuators 302, 303 can be configured to apply an oscillating torque to the flexible plate 352 to drive the flexible plate to vibrate in a torsional mode at a selected frequency. The torsional mode may be a resonance frequency of the flexible plate, including the fundamental frequency but also even and uneven harmonics. The torsional mode may be a 2ndharmonic oscillation, 3rdharmonic oscillation or 4thharmonic oscillation, but also higher harmonics may be applied. In Fig.2A-2B the actuators 302, 302 are positioned at 3 / 8 and 5 / 8 of the length of the flexible plate. Sensors or sensor system 301 , 304 for detecting the result of the interaction between the fluid flow and the actuated flexible plate 352 are positioned in positions corresponding to 1 / 8 and 7 / 8 of the length of the flexible plate. These positions (1 / 8, 3 / 8, 5 / 8, 7 / 8) correspond to the positions of the amplitude maxima of a 4thharmonic oscillation of the flexible plate.

[0057] At least two actuators may be used. A net sum of the at least two oscillating torques applied to the flexible plate by the at least two actuators may be zero or substantially zero. The at least two oscillating torques may have opposite directions. A sum of the at least two oscillating torques may be less than the largest of the at least two oscillating torques. If e.g. applying three oscillating torques the sum of all the oscillating torques should be zero or substantially zero.

[0058] As mentioned, the mass flow meter 310 can also include a sensor system 301 , 304 to measure the interaction between the mass flow and the flexible plate vibrating in torsion. The sensor system 301 , 304 may be configured to measure movement of the flexible plate 352 as a function of time. The sensor system 301 , 304 may measure the movement of the flexible plate at positions upstream and downstream of the longitudinal centre C with respect to the flow of fluid Vx351 . The movement of the flexible plate 352 can be characterized by any parameter of the flexible plate that oscillates as a function of time when the flexible plate vibrates in torsion. Example parameters can include, but are not limited to, linear and / or angular parameters such as position, speed, acceleration, and displacement. In certain embodiments, angle, angular speed, and angular acceleration can be measured. In other aspects, stress and / or strain can be measured. The sensor system 301 , 304 may be in the form of pickup sensors arranged at positions along the tubular housing. The pickup sensors may measure rotational speed and direction of the flexible plate.

[0059] The sensor system 301 , 304 may include a number of sensors arranged in different positions in the mass flow meter. The sensor system may be arranged in positions where the flexible plate exhibits the largest movement during excitation by the applied torque. In Fig. 1 A, 1 B the sensor system is as earlier described, provided with two sensors positioned where the 4thharmonic oscillation of the flexible plate has maximum amplitudes. These positions are at 1 / 8, 3 / 8, 5 / 8, 7 / 8 of the length of the flexible plate. Measurement of the largest parameter values ensures a large signal output from the sensor system and thus an increased sensitivity. Actuating the flexible plate by the actuating system in positions of the largest amplitudes, results in a higher energy transfer to the flexible plate also contributing to an improved sensitivity for the mass flow sensor. Using two sensors, a first sensor may be positioned at 1 / 8 and a second sensor at 7 / 8 of the length of the flexible plate as illustrated in Fig.1 A. This leaves space for the positioning of the actuating systems at 3 / 8 and 5 / 8 of the length of the flexible plate as illustrated in Fig.lA and as explained above. Driving the flexible plate in 2nd, 3rd, 4thand higher harmonics may increase the Q-factor and the sensitivity of the mass sensor. The Q-factor is in simplified terms in this context a relationship between the energy of the flexible plate in an oscillating behavior and the energy input into the flexible plate to provide the oscillating behavior. In general, the resulting torsion applied to the flexible plate should be in a position where an applied torque result in an oscillating behavior with large amplitudes of the flexible plate. In these positions with the largest amplitudes, the flexible plate will also experience the largest changes in speed and acceleration when exposed to the fluid flow. These changes are measured by the sensor system of the mass flow meter. The positioning of sensors and actuating system in positions corresponding to the 4thharmonics of the flexible plate, may also be used for 2ndand 3rdharmonics. The positioning of the sensors and actuating system would then also be close to the amplitude maxima for the oscillations of the flexible plate. The embodiment illustrated in Fig.lA, 1 B enable the mass flow meter to be driven in both uneven and even harmonic states offering flexibility of the mass flow meter and the possibility of adaption of the mass flow meter to the actual flow situation and the information desired from the mass flow meter. Even harmonic states provide an oscillation torque where a net sum of the oscillating torques applied to the flexible plate is zero or substantially zero. It may be possible to drive the mass flow meter in several modi simultaneously to enable detection of mass flow in a two-phase flow such as, e.g. a liquid flow with bubbles. This may be advantageous for measurement of mass flow for e.g. CO2, NH3, H2 or LNG.

[0060] The mass flow meter may be arranged inside a pipeline. The tubular housing is then not exposed to pressure from the surroundings enabling use of the mass flow meter in high pressure environments. This enable the tubular housing to be made of a much thinner and lighter material than the pipeline. The tubular housing may be a liner. The liner may be made of non-magnetizable material. The liner may be made of an electrically conducting or electrically non-conducting material. A pressure housing may be arranged outside the liner. The pressure housing may be made of an electrically conducting material. The space between the pressure housing and the liner may be filled with a liquid or solid filler material to transfer the pressure from the fluid flow 351 on the inside of the liner 391 and out to the pressure housing. As the tubular housing may be a liner it does not need to withstand the high pressure of the fluid flow. This solution may e.g. be used for measuring high pressure fluids. For measurements of high-pressure fluids, the outer pressure housing would be thick to be able withstand the pressure. For a thick pressure housing, use of prior art electromagnetic actuators would not be possible. Prior art electromagnetic actuators also have problems with eddy currents in the outer pressure housing resulting in dissipation of energy and reduced efficiency.

[0061] The transducers disclosed in this disclosure may be used as actuators or pick-ups or both actuators and pick-ups for a sensor, in particular a sensor with a tube-in- tube construction, a sensor with a tubular housing arranged inside the high- pressure pipeline, and a mass flow meter. The sensor may be adapted for high- pressure measurements of high-pressure fluids inside a pipe system. The mass flow meter comprising a tubular housing arranged inside an outer tube. A current in a main current path of the transducer provides a magnetic field. A magnetic field may also induce current in the main current path. When the transducer is used as an actuator for a sensor, current in the main current path may thus induce at least one torque in a flexible plate of the sensor. The current in the main current path may be an oscillating current inducing an oscillating torque in the flexible plate. The flexible plate is provided with magnetizable or magnetic material which e.g. may be permanent magnets. The transducer may also function as a pick-up for the sensor, in particular a mass flow meter. When the transducer function as a pick-up for the sensor, the flow of fluid through the tubular housing induces vibrations in the flexible plate. The vibrations in the flexible plate induce current in the main current path. The current in the main current path may be measured.

[0062] Figure 2 illustrates in perspective view an exemplary embodiment of a sensor 100 provided with two transducers 120. The transducers may function as an actuator and / or a pick-up for the sensor 100. The sensor may be a mass flow meter. The sensor is arranged on the inside of an outer tube 101 . The sensor has a tubular housing 102 and is arranged on the inside of the outer tube 101 . The tubular housing 102 of the sensor and the outer tube 101 provides a tube-in-tube system. The outer tube working as a pressure containing part for the sensor. The sensor is provided with a flexible plate 103 arranged within the tubular housing 102. The flexible plate is able to vibrate in torsion as described above for Fig.1A-1C. The flexible plate is provided with a magnetic or magnetizable material 104.

[0063] In Figure 2, a transducer 120 is provided on the upper side and on an underside of the sensor 100. The transducers are arranged on opposite sides of the sensor. The two transducers have the same construction. The terms upper and lower are used for explanation of the sensor and transducers illustrated in the Figures of this disclosure. The sensor 100 may however in use be arranged in all kinds of positions, and upper and lower should not be considered as limiting for the invention. In the following, the transducer on the upper side of the sensor in Fig.2 will be described. The transducer includes an electrically conductive material 105 embedded in the tubular housing 102. Alternatively, the electrically conductive material may be embedded in the outer tube 101. The electrically conductive material 105 provides a main current path of the transducer. The current in the main current path provides a magnetic field. Current in the main current path may thus induce at least one torque in the flexible plate 103 via the magnetic or magnetizable material 104. The current in the main current path may be an oscillating current inducing an oscillating torque in the flexible plate 103 via the magnetic or magnetizable material 104. The magnetizable or magnetic material may e.g. be permanent magnets. The transducer may function as an actuator for the sensor 100. The transducer may also function as a pick-up for the sensor 100. When the transducer function as a pick-up for the sensor 100, the flow of fluid through the tubular housing 102 induces vibrations in the flexible plate 103. The vibrations in the flexible plate induce current in the main current path via the magnetic or magnetizable material 104. The current in the main current path may be measured.

[0064] The transducer 120 in Figure 2 has two electrical conductors 109 accessible from the outside of the outer tube 101 . The electrical conductors may be connected to an external power supply. The electrical conductors may be connected to a measurement device. The electrical conductors are illustrated connected to the outside of the outer tube in Fig.2. The electrical conductors may alternatively be connected directly to the embedded electrically conductive material 105. The electrical conductors 109 in Fig.2 are connected to the outer tube in positions above the end surfaces of the embedded electrically conductive material 105. The end surfaces have a larger diameter than the middle part of the electrically conductive material as illustrated in Fig.2. The electrically conductive material may e.g. have a dog bone shape. The outer tube 101 and the inner tube 102 may be made of materials with a specific conductance lower than the specific conductance of the embedded electrical material 105. The electrical conductors 109 are arranged over the end parts of the embedded electrically conductive material 105 in order for the current supplied to the electrical conductors 109 to be able to reach through the outer tube and the tubular housing that are made of materials with poor conductivity. The outer tube and the tubular housing may also lead leakage currents from the electrical conductors 109, that should be minimized. Placing the electrical conductors 109 directly above the end parts of the embedded electrical material 105 also reduces the leakage currents.

[0065] Figure 3 is a cross-sectional view along a longitudinal direction illustrating an exemplary embodiment of sensor 100 with a tubular housing 102 arranged on the inside of an outer tube 101. The sensor may be a mass flow meter. The tubular housing 102 is arranged on the inside of the outer tube 101 , wherein the outer tube working as a pressure containing part for the sensor. The sensor is provided with at least one flexible plate 103 arranged within a tubular housing 102. The flexible plate 103 is provided with a magnetic or magnetizable material 107. Further details of the magnetic or magnetizable material 107 will be described later. The sensor is provided with two transducers. The two transducers have the same construction. The outer tube working as a pressure containing part for the sensor. The sensor is provided with two transducers. The two transducers are arranged on opposite sides of the sensor. The transducer has an external coil on the outside of the outer tube 101 . The sensor is provided with two transducers. Each transducer includes an electrically conducting material 105 embedded in the tubular housing 102. The sensor may be a mass flow meter.

[0066] Each transducer includes an electrically conducting material 105 embedded in the tubular housing 102. An electrical conductor in the form of a winding 110 is arranged on the outside of the outer tube 101 . The winding 110 is connected to the surface of the outer tube in positions above the two end surfaces of the embedded electrically conducting material 105. The embedded electrical conductor 105 and the winding 110 provide the main current path of the transducer. The electrical conductor may also serve as a magnetic field return path for the electrically conducting material 105. In Figure 3, the transducer is provided with an external coil 112 on the outside of the outer tube 101 . The external coil may have at least one winding. The external coil provides a power supply for the transducer close to the surface of the outer tube reducing loss of current and enabling a higher torque applied to the flexible plate via the magnetic field. The current in the main current path may be induced by the external coil 112. The external coil 112 has a core 111 , preferably of iron. The electrically conducting winding 110 passes through the core of the primary coil 112. The electrically conducting winding 110 and the external coil 112 thus have a common core. The common core may be an iron core. The electrically conducting winding 110 is in Figure 3 a single conductor, preferably an uninsulated conductor. The external coil 112 and the single winding (secondary winding) 110 are wound around a common core 111. The transducers may be used as actuators inducing at least one torque in the flexible plate via the magnetic or magnetizable material as explained above. The external coil is a primary winding and the single winding a secondary winding for an actuator. The transducers may be used as pick-ups where the movements of the flexible plate induce a current in the main current path via the magnetic or magnetizable material as explained above. The single winding is a primary winding and the external coil a secondary winding for a pick-up.

[0067] Figure 4 is a cross-sectional view along a longitudinal direction illustrating an exemplary embodiment of the sensor 100 from Figure 3. A tubular housing 102 is arranged on the inside of an outer tube 101 . The outer tube working as a pressure containing part for the sensor. The sensor may be a mass flow meter. The sensor is provided with at least one flexible plate 103 arranged within a tubular housing 102. The flexible plate is provided with a magnetic or a magnetizable material 107. The sensor is provided with two transducers. Each of the transducers includes an electrically conducting material 106 embedded in the outer tube 101. This is in contrast to Figure 3, where the electrically conductive material is embedded in the tubular housing. As the electrically conductive material is embedded in the outer tube in the exemplary embodiment in Fig.4, this reduces the distance between the electrical conductor 110 on the outside of the outer tube and the embedded electrically conductive material 106. This reduces the leakage current and increases the current density in the areas where the electrical conductor is above, and preferably directly above, the end areas of the embedded electrically conductive material 106. The transducer in Figure 4 may be used as an actuator and / or a pick-up for the sensor.

[0068] Figure 5 illustrates in longitudinal cross-section an exemplary embodiment of a sensor 100 with a tubular housing arranged on the inside of an outer tube 101 working as a pressure containing part for the sensor. The sensor is provided with at least one flexible plate 103 arranged within a tubular housing 102. The flexible plate is provided with a magnetic or magnetizable material 107. The flexible plate has four vanes. The magnetic or magnetizable material are arranged on each vane. The sensor is provided with four transducers 120. The transducers have the same construction. The transducers are arranged in pairs opposite of each other around the sensor 100 in the same longitudinal position on the sensor 100. Each of the transducers includes an electrically conducting material 105 embedded in the tubular housing 102. The sensor may be a mass flow meter.

[0069] Each of the transducers illustrated in Fig. 5 comprises an external coil arranged on the outside of the outer tube 101 . The transducers are arranged on opposite sides of the outer tube 101 . The number of transducers may be provided depending on the sensor design. An electrically conducting material 105 is arranged on the inside of the outer tube 20. The electrically conductive material is embedded in the tubular housing 102. All of the transducers have the same construction. In the following, the transducer is explained in detail. The transducer has a primary coil 112. Transducers has a secondary winding 110. The primary coil 112 has multiple windings. The multiple windings are wound around a core. The windings are electrical conductors. The core may be ring shaped with a center opening. The core may have a donut shape with a center opening. The core may be of iron. The secondary winding 110 may be a single winding. The primary coil has a central opening formed by the core. A winding 110 is arranged on the outside of the outer tube 101. The winding is a single electrical conductor. The single electrical conductor may be an uninsulated conductor. The winding 110 passes through the ring-shaped core of the primary coil. The winding 110 is in contact with the surface of the outer tube 101 in two locations. The two locations are in the same two longitudinal positions on the surface of the outer tube for the two opposite transducers facing each other on opposite sides of the outside of the outer tube as illustrated in Fig.5. The electrically conducting material 105 is embedded in the tubular housing 102 forming a main current path. The electrically conducting material 105 may extend in the longitudinal direction with ends having a larger diameter / width as explained above. The electrically conducting material may have a dog bone shape as explained above. The dog bone shape has larger areas on each side connected with a more longitudinal shaped part in the middle.

[0070] The single winding conductor contacts the outer tube 101 in the positions corresponding to the positions of the larger diameter / width ends of the embedded electrically conducting material 105 forming the main current path. The single winding conductor 110 and the electrically conducting material 105 form a closed electrical circuit forming a secondary coil. Current travels through the single conductor 110 and through the outer tube 101 and to the inside of the outer tube 101 and then travels through the electrically conducting material 105 arranged on the inside of the outer tube and then travels through the single conductor 110 from the inside of the outer tube 101 to the outside of the outer tube. The closed electrical circuit formed by the single conductor 110 and the electrically conducting material 105 creates a magnetic field with a magnetic field vector perpendicular to the travel direction of the current through the single conductor and the electrically conducting material 105. The magnetic field extends on the inside of the outer tube. The magnetic field induces a torque in the flexible plate via a magnetic or magnetizable material of the flexible plate. The magnetic or magnetizable material may be arranged on the surface of the flexible plate or embedded in the flexible plate. The current in the main current path may be an oscillating current inducing an oscillating torque in the flexible plate. The flexible plate is provided with four vanes that may vibrate in torsion as explained above. The magnetic or magnetizable material is provided in each vane of the flexible plate.

[0071] The transducers of Figure 5 may also be used as pick-ups for the mass flow meter. Vibrations in the flexible plate caused by the through-flow of fluid through the tubular housing of the mass flow meter induce current in the main current path via the magnetic or magnetizable material of the flexible plate. The current may be measured by the primary coil 112.

[0072] The outer tube 101 of the transducer may be provided with holes or with throughgoing openings 115 in areas of the main current path. Fig. 6, 8, 9 and 13 illustrate exemplary embodiments where parts of the outer tube are removed.

[0073] Figure 6 is a cross-sectional view along a longitudinal direction illustrating a further exemplary embodiment of the sensor 100 from Figure 2 with a tubular housing 102 arranged on the inside of an outer tube 101 . The outer tube working as a pressure containing part for the sensor. The sensor is provided with at least one flexible plate 103 arranged within the tubular housing 102. The flexible plate is provided with a magnetic or magnetizable material 107. The sensor is provided with two transducers. Each of the transducers includes an electrically conducting material 105 embedded in the tubular housing 102. The transducers also include electrical conductors 109 arranged on the outside of the outer tube. In the exemplary embodiment in Figure 6, the outer tube is provided with holes or through-going openings 115 for the electrical conductors 109. In Figure 6, the electrical conductors 109 extend through the outer housing 102 through the holes or through-going openings. The electrical conductors 109 are in direct contact with the embedded electrically conducting material 105. The electrically conducting material 105 embedded in the tubular housing 102 also has a reduced thickness in the exemplary embodiment of Figure 6 in the areas contacting the electrical conductors 109. Reducing the thickness avoids unnecessary material as embedding electrically conducting material in the tubular housing may reduce the strength of the tubular housing. The sensor may be a mass flow meter. The transducer in Figure 6 may be used as an actuator and / or a pick-up for the sensor.

[0074] Figure 7 illustrates in longitudinal cross-section an exemplary embodiment of a sensor 100 with a tubular housing arranged on the inside of an outer tube 101 working as a pressure containing part for the sensor. Figure 7 is a further exemplary embodiment of the exemplary embodiment from Fig. 5. The transducers have external coils on the outside of the outer tube 101 . The embodiment in Figure 7 differs from the embodiment in Figure 5 disclosed above as each of the transducers further includes a magnetic material 116 embedded in the tubular housing. The magnetic material 116 in the embodiment in Figure 7 is arranged on each side of the electrically conducting material 105 embedded in the tubular housing. The sensor is provided with at least one flexible plate 103 arranged within a tubular housing 102. The flexible plate is provided with a magnetic or magnetizable material 107. Four transducers are provided for the sensor. Each of the transducers includes an electrically conducting material 105 and a magnetic material 116 embedded in the tubular housing 102. The arrangement of a magnetic material adjacent to the electrically conducting material 105 allows an electrically conducting material with reduced thickness. The embedded magnetic material 116 increases the field strength of the electromagnetic field provided by the main current path. When the transducer functions as a pick-up, the embedded magnetic material 116 may also increase the magnetic field provided by the magnetic or magnetizable material in the flexible plate. The embedded magnetic material 116 also increases the strength of the tubular housing. The sensor may be a mass flow meter. The magnetic material 116 is arranged in a longitudinal direction on each side of the embedded electrically conducting material 105. The transducer in Figure 7 may be used as an actuator and / or a pick-up for the sensor.

[0075] Figure 8 illustrates in perspective view an exemplary embodiment of a sensor 100 with a tubular housing 102. The sensor may be a mass flow meter. The sensor is provided with a transducer. Embedding the electrically conducting material in the tubular housing may reduce the strength of the tubular housing. The outer tube provides increased strength to the tubular housing. An outer tube 101 is provided as a reinforcement for the sensor in the area of the transducer. The outer tube is provided in the area of the transducer between the two electrical conductors 109. The transducer in Fig.8 includes an electrically conducting material 105 embedded in the tubular housing 102. The transducer also includes a magnetic material 116 embedded in the tubular housing 102. The magnetic material may be embedded in areas of the tubular housing 102. In Figure 8, the magnetic material 116 is arranged in a longitudinal direction on each side of the embedded electrically conducting material 105. The embedded electrically conducting material 105 has a reduced thickness in the enlarged end areas under the electrical conductors 109. Minimizing the material also minimizes the loss of current and at the same time avoiding a too low current density. The magnetic material 116 is arranged on each side of the middle part of the embedded electrically conducting material as illustrated in Fig.8. The embedded electrically conductive material 105 and the two electrical conductors 109 on the outside of the tubular housing form the main current path of the transducer. The magnetic material 116 contributes to the strength of the tubular housing and strengthens and directs the magnetic field induced by the current in the main current path in a flexible plate (not shown) arranged on the inside of the tubular housing. The flexible plate may be provided with magnetic or magnetizable material (not shown) as explained above for e.g. Figure 2. The transducer in Figure 8 may be used as an actuator and / or a pick-up for the sensor. Figure 9 is a cross-sectional view along a longitudinal direction illustrating an exemplary embodiment of a sensor 100 with a tubular housing 102 arranged on the inside of an outer tube 101 . The outer tuber working as a pressure containing part for the sensor. The sensor is provided with at least one flexible plate 103 arranged within the tubular housing 102. The flexible plate is provided with a magnetic or magnetizable material 107. The sensor is provided with two transducers. Each of the transducers includes an electrically conducting material 105 embedded in the tubular housing 102. The transducers also include electrical conductors 109 arranged on the outside of the outer tube. In the exemplary embodiment in Figure 9, the outer tube 101 is provided with holes or through- going openings 115 for the electrical conductors 109. In Figure 9, the electrical conductors 109 extend through the outer housing 102 through the holes or through-going openings. The electrical conductors 109 are in direct contact with the embedded electrically conducting material 105. The holes or throughgoing openings 115 in the outer tube are provided in areas of the main current path. Each transducer includes two electrical conductors 109. The two electrical conductors 109 form a pair. The pair of electrical conductors may be connected to a power supply forming an electrical circuit with the embedded electrically conducting material. The pair of electrical conductors may form a circuit with the embedded electrically conducting material and current induced in the circuit. The sensor may be a mass flow meter. The transducer in Figure 9 may be used as an actuator and / or a pick-up for the sensor.

[0076] Figure 10 illustrates an exemplary embodiment of the transducer from Figure 9 where the transducers are provided with an external coil. The external coil may be as explained above for e.g. Figures 3 and 4. The transducer in Figure 10 may be used as an actuator and / or a pick-up for the sensor.

[0077] Figure 11 illustrates an exemplary embodiment of the transducer from Figure 6. In Figure 11 , the two transducers are provided with an external coil. In the transducers in Figure 11 the electrically conducting material 105 embedded in the tubular housing 102 has a reduced thickness in the areas contacting the electrical conductor 109. The external coil may be as explained above for e.g. Figures 3 and 4. The transducer in Figure 11 may be used as an actuator and / or a pick-up for the sensor.

[0078] Figure 12A illustrates an exemplary embodiment of a sensor 100 with a tubular housing arranged inside an outer tube. The outer tuber working as a pressure containing part for the sensor. The sensor is provided with a flexible plate 200 arranged within the tubular housing. The sensor is provided with three groups 201 , 202, 203 of transducers arranged along the length of the outer tube. Each group of transducers has four transducers arranged in different positions around the outer tube. The four transducers have the same construction. The four transducers are arranged in pairs opposite of each other around the sensor 100 in the same longitudinal position on the sensor 100. The two opposite transducers facing each other on opposite sides of the outside of the outer tube. The transducers in each group are symmetrically arranged around the sensor. Each of the transducers in the different groups are also arranged in the same circumferential position on the sensor as the corresponding transducer in the other groups of transducers. Each of the transducers includes an electrically conducting material 105 embedded in the tubular housing 102. The transducers are symmetrically arranged around the sensor to obtain contributing torques acting on all the vanes of the flexible plate as illustrated and explained for Fig.1A-1C. The construction of each of the transducers is explained above for Figure 5. The sensor may be a mass flow meter.

[0079] In the exemplary embodiment illustrated in Fig.12A three groups of transducers 201 , 202, 2023 are shown. The first group of transducers 201 may be arranged in position 1 / 4 of the longitudinal length of the flexible plate. The second group of transducers may be arranged in position 2 / 4 of the longitudinal length of the flexible plate. The third group of transducers may be arranged in position 3 / 4 of the longitudinal length of the flexible plate. This arrangement of the transducers corresponds to the 3rd harmonic excitation of the flexible plate as explained earlier for Fig.2A-C.

[0080] Fig.12B show a longitudinal cross-section of the exemplary embodiment of

[0081] Fig.12A. Only the two perpendicular vanes of the flexible plate are shown from a side together with the transducers on top and on the underside of the sensor. A group of magnetic or magnetizable material is arranged on each vane. The groups of magnetic or magnetizable material is positioned beneath each embedded electrically conducting material. The circles represent the two horizontally arranged vanes of the flexible plate. The terms horizontal, vertical, upper and lower are only used for more easily describing the embodiment and the interrelation of the different parts of the sensor and transducers, but are not to be considered limiting for the invention.

[0082] Figure 13 is an exemplary embodiment of the sensor in Figure 8 where the electrical conductors 109 are in the form of a winding 109 forming a coil arranged on the outside of the tubular housing. In Figure 13, the transducer also further includes a coil arranged on the outside of the tubular housing. The coil and the electrically conducting material embedded in the tubular housing form the main current path of the transducer.

[0083] Figure 14 illustrates the sensor in Fig.5 in a cross-sectional view. In Fig.14 two transducers are illustrated with the electrically conducting material 500 arranged in the inner housing centrally positioned under the single electrically conducting winding.

[0084] The electrically conductive material 105 may have a longitudinal shape with areas with larger diameters at its ends. The electrically conducting part illustrated in e.g. Fig.2 has a dog bone shape. The outer parts; i.e. the two parts with the largest diameter of the electrically conducting material, are arranged below the two electrical conductors 109. The longitudinal shape of the electrically conducting material 105 with areas with larger diameters at its ends; e.g. the dog bone shape, increases the area of the electrically conducting material, which enables efficient and low loss transfer of current through the electrically conducting material. The longitudinal shape of the electrically conducting material 105 with areas with larger diameters at its ends is also illustrated in e.g. Fig.12 and 14. Other shapes may be envisaged as e.g. a rectangular shape. The end areas of the electrically conducting material should be adapted to the electrical conductors 109. Arranging the electrically conductive material on the inside of the outer tube reduces the distance to the magnetizable material arranged on the flexible plates inside the tubular housing which also considerably reduces the loss of electrical power. The electrically conducting material 105 may be embedded in the outer tube or tubular housing. This may be done by e.g. milling out a portion of the outside of the tubular housing or outer tube and inserting the electrically conducting material into the milled out portion.

[0085] The electrical conductors and the electrically conducting material may e.g. be of metal. The tubular housing may be of a non-magnetic material. The tubular housing may be a poor electrical conductor and may be of an insulating material. The outer tube may be made of a magnetic material. The use of these materials may reduce the costs for the coil system.

[0086] The outer tube and the tubular housing may be welded together. There may be no isolation between the outer tube and the tubular housing. The tubular housing may in a typical example have an inner diameter of about 50mm. The thickness of the outer tube may depend on the dimension of the pipe. The thickness of the tube may e.g. be about 10% of the inner diameter of the pipe. A typical area of the electrically conducting material arranged in or embedded in the tubular housing may be about 2 x 2 mm.

[0087] A ratio between a specific conductance of the electrically conducting material 105 embedded in the tubular housing 102 or embedded in the outer tube 101 and the material of the outer tube 101 may be at least 8: 1 , preferably 10: 1 or most preferably 20:1 . The ratio between the specific conductance of the electrically conducting material 105 embedded in the tubular housing 102 or embedded in the outer tube 101 and the material of the tubular housing 102 may be at least 8:1 , preferably 10:1 or most preferably 20:1.

[0088] The electrical conductor 109, the primary winding 112 and the secondary winding 110 may be made of at least one of Cu, Ag, Au or Al.

[0089] The outer tube 101 may be made of a metal of low conductivity. The outer tube may be made of a magnetic material, a soft magnetic material, magnetic steel, carbon steel or nickel alloys. The electrically conducting material 105 may be made of at least one of Cu, Ag, Au or Al (copper, silver, gold or aluminum). The electrical conductor 109 be made of at least one of Cu, Ag, Au or Al. The tubular housing 102 may be made of a non-magnetic material. The tubular housing may be made of a non-magnetic metal. Areas of magnetic material may be embedded in the tubular housing.

[0090] The tubular housing 102 and the outer tube 101 may be bonded together by direct fusion, soldering, welding, diffusion welding or bracing. The tubular housing 102 and the electrically conducting material 105 embedded in the tubular housing may be bonded together by direct fusion, soldering, welding, diffusion welding or bracing. The outer tube 101 and the electrically conducting material 105 embedded in the outer tube may be bonded together by direct fusion, soldering, welding, diffusion welding or bracing.

[0091] The transducer may be used as an electromagnetic actuator for a sensor arranged inside the outer tube. The transducer may be used as a pickup for a sensor arranged inside the outer tube. When the transducer functions as a pick-up for the sensor, the flow of fluid through the tubular housing induces vibrations in the flexible plate. The vibrations in the flexible plate induce current in the main current path via the magnetic or magnetizable material. The current in the main current path may be measured with a measuring device.

[0092] The primary coil is arranged close to the outer surface of the outer tube. Any need of an electrical cable connection is thus avoided. A cable connection may not in all embodiments provide sufficient current to drive the transducer. High current and low voltage are needed. Alternating current (AC) in the secondary coil of e.g.10A and a low voltage of 10pV may be provided by the primary coil driven by a transformer. Low voltage electronics may be used for controlling the transducer.

[0093] The transducer allows for increased thickness of the outer tube as the secondary coil are arranged partly on the inside and partly of the outside of the outer tube. The secondary coil may enter through the surface of the outer tube and to the inside of the outer tube by a single wire electrical conductor. A single wire electrical conductor may transport a lot of current. Together with the primary coil on the outside of the outer tube, a higher electrical current may be induced into the primary coil and transported to the inside of the outer tube. This provides a magnetic field on the inside of the outer tube with low loss of power.

[0094] The arrangement of the electrically conducting material on the inside of the outer tube creating a magnetic field on the inside of the outer tube and also on the outside of the outer tube. The outer tube may be provided with a return path for the magnetic field on the outside of the outer tube. The single winding electrical conductor may also function as a magnetic field return path for the magnetic field from the magnetic or magnetizable material arranged inside the inner housing.

[0095] The coil system with primary coil on the outside and the secondary coil partly on the outside and inside of the outer tube, also reduces the problem with eddy currents in the prior art solutions. Providing the magnetic field by the current in the single winding conductor and the electrically conducting part on the inside of the outer tube and closed to the sensor, reduces the current required for generating sufficient magnetic field strength for the sensor, and therefore also the eddy currents caused by the changing magnetic field caused by the current.

[0096] The coil system may be used as an electromagnetic actuator. The coil system may also be used as a pick-up sensor for a sensor arranged inside an inner tube. The sensor may be a mass flow meter.

[0097] The electrically conducting material is embedded in the tubular housing. The electrically conducting material may serve to reinforce the inner housing and providing increased structural strength.

[0098] In the exemplary embodiments, the vanes of the flexible plate are arranged in a cross-configuration with each vane arranged at an angle of 90 degrees with respect to each other. The angles between the vanes depends on the number of vanes. Use of two vanes provides an angle of 180 degrees between the vanes. Use of eight vanes provides an angle of 45 degrees between each of the vanes. The magnetizable or magnetic material is arranged on each vane. Only the magnetic or magnetizable material are shown to illustrate their position with respect to the electrical conductors 109 and embedded magnetic material 107 providing the magnetic field interacting with the magnetic or magnetizable material inside the tubular housing. The electrical conducting material 105 embedded in the tubular housing is arranged in parallel with the longitudinal direction of the inner housing and thus also in parallel with the longitudinal direction of the flexible plates. The electrical conductors 109 are arranged above the end parts of the electrical conducting material 109. This arrangement provides magnetic force fields perpendicular to the magnets or magnetizable material on the vanes of the flexible plate enabling the flexible plate to vibrate in torsion. Also, when the transducer arrangement is used as a pick-up, this arrangement provides efficient induction of current in the main current path by the magnets or magnetizable material provided on the flexible plate when the flexible plate vibrates in torsion.

[0099] The electrically conducting material may in other exemplary embodiments be arranged on the outside of the tubular housing. Arranging the electrically conducting material on the outside of the outer tube may however result in larger loss of power as compared to a solution with the electrically conducting material on the inside of the outer tube.

[0100] Figures 3, 4, 6, 9, 10, 11 , 12B illustrates in longitudinal cross-section exemplary embodiments of a sensor 100. The vanes of the flexible plate 103 is provided with two groups of magnets or magnetizable material 107. Each group of magnets or magnetizable material may be provided by permanent magnets or magnetic material arranged side by side. The permanent magnets may be bar magnets. The two groups of magnets may be arranged on the outer surface of the flexible plate or may be embedded in the flexible plate. Alternatively, the groups of magnets may e.g. be provided by portions of the flexible plate formed from a magnetic material (e.g., metals, metal alloys, steels, polymers, etc.).

[0101] The groups of magnets may be arranged on the flexible plate in positions within the magnetic field from the winding 110 and the magnetizable material with the largest magnetic field strength. In e.g. Fig.3 the groups of magnetic or magnetizable material are arranged in a centred position under the single winding electrical conductor 110.

[0102] The groups of magnets may have different magnetic pole configurations with respect to each other. The groups of magnets may have different configurations adapted to the construction and use of the transducer.

[0103] The Figures 3, 4, 6, 9, 10, 11 , 12B illustrate two 4-group dipoles of permanent magnets. The permanent magnets may be in the form of dipole magnetic bars arranged side by side within each group.

[0104] A group of magnets may form a North pole or a South pole.

[0105] The groups of magnets may be arranged to form a quadrupole cross section of a flexible plate with four vanes as e.g. in Fig.5, 7, 12A. The groups of magnets in the four vanes of the flexible plate may be arranged with alternating magnetic poles (e.g. north, south, north, south) facing outwards towards the main current path. For a 4-group dipole cross section of permanent magnets the magnets may be arranged with pairs of magnetic poles facing outwards (north, north, south, south). A 2-group dipole cross section of permanent magnets, the magnets in the vanes may be arranged with different magnetic poles facing outwards (north, south,) forming a dipole.

[0106] Groups of permanent magnets may be arranged in each of the four vanes of the flexible plate. Each group of magnets may be formed by dipole bar magnets arranged side by side forming a dipole. The direction of the dipole may be altered from one vane to the next vane. As an example, in a first vane the north pole N points outwards and in the second vane the north pole N points inwards, in the third vane the north pole N points outwards and in the fourth vane the north pole N points inwards. The south poles S of the first vane and the third vane face each other, and the north poles for the second vane and the fourth vane face each other. The groups of magnets facing each other also have dipoles facing each other. The groups of magnets may be arranged around the longitudinal center of the flexible plate. The groups of permanent bar magnets arranged side by side with the same pole facing the same way (symmetrically arranged) form a dipole in each vane of the flexible plate. In this embodiment the two groups of magnetic dipoles of each vane have the same direction. The electromagnetic actuator may be driven with current of opposite phase (anti-symmetrically) to apply a torsion to the flexible plate providing a 4thharmonic oscillation of the flexible plate.

[0107] The configuration of the groups of magnets may vary. The groups of magnets illustrated in e.g. Fig. 3 and 4 may form a quadrupole in the transducer configuration in Fig.5. Using eight vanes and one group of magnets in each vane, this would form an octupole. Multipole arrangements of permanent magnets increase the torsion for the same applied current. In the illustrated embodiments in Figures 3, 4, 6, 10, 11 bar magnets are used, but also round magnets may be used. Also, several groups of magnets may be provided along the longitudinal direction in each vane depending on the number of transducers and the arrangement of the main current path around and along the longitudinal direction of the outer tube.

[0108] Groups of magnets may be symmetrically arranged (not shown) along the longitudinal direction of the vane. Groups of magnets may also be antisymmetrically arranged along the longitudinal direction of the vane (not shown) where the poles of a group of magnets have opposite direction in different positions in the same vane. The current in the main current path of the actuating system for anti-symmetrically arranged groups of magnets, are in phase (symmetrical) to apply a net sum of the at least two oscillating torques applied to the flexible plate being zero or substantially zero. The at least two oscillating torques have opposite directions. A sum of the at least two oscillating torques may be less than the largest of the at least two oscillating torques.

[0109] By controlling the phase of the current applied to the transducer, oscillating torques of opposite directions may be applied to each of the vanes of the flexible plate due to alternation of the direction of the dipole between the vanes. The frequency of the current may also be controlled to torsionally excite the flexible plate in a harmonic oscillation and the magnitude of the current controlled to provide a desired amplitude of the oscillations of the vanes.

[0110] The transducers may be connected to a controller or e.g. computing device for controlling the current supplied to the transducers for generating the magnetic field. At least one of the magnitude, frequency and / or phase of the current applied to the main current path may be controlled to enable generating one or more magnetic field(s) to apply an oscillating torque to the flexible plate. The flexible plate may be driven at resonance frequency both at fundamental frequency, but also at even and uneven harmonics. The controller may e.g. be a computer or power supply. The transducers may be configured to receive feedback e.g. from a feedback sensor system of the mass sensor to drive the flexible plate at resonance.

[0111] The transducer may also function as a pickup sensor. A pickup sensor for e.g. a sensor in the form of a mass flow meter 310 can measure the interaction between e.g. a mass flow and the flexible plate vibrating in torsion. The groups of magnets arranged on the flexible plate induces currents in the main current path due to the movement of the flexible plate by the mass flow as a function of time. The movement of the flexible plate 352 can be characterized by any parameter of the flexible plate that oscillates as a function of time when the flexible plate vibrates in torsion. Example parameters can include, but are not limited to, linear and / or angular parameters such as position, speed, acceleration, and displacement. In certain embodiments, angle, angular speed, and angular acceleration can be measured. In other aspects, stress and / or strain can be measured. Rotational speed and direction of the flexible plate may also be measured by the coil system.

[0112] Each transducer may be controlled to switch between an actuating mode applying an oscillating torque to the flexible plate and a detecting mode detecting movements of the flexible plate. The mode switching may be performed continuously or intermittently during measurement by the sensor. The transducers may be connected to a computing device or controller or other device receiving. The computer device, controller or other device may also control each transducer. The sensor may be a mass flow meter with at least one flexible plate arranged within the tubular housing. For a mass sensor with a flexible plate arrangement, the number of transducers also depend on the number of vanes of the flexible plate.

[0113] Having described example embodiments of the invention it will be apparent to those skilled in the art that other embodiments incorporating the concepts may be used. These and other examples illustrated above are intended by way of example only and the actual scope of the invention is to be determined from the following claims.

Claims

CLAIMS1 . A transducer for a mass flow meter, where the mass flow meter is arranged inside an outer tube working as a pressure containing part for the mass flow meter, the mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, the flexible plate provided with a magnetic or magnetizable material; the transducer comprising: an electrically conducting material embedded in the tubular housing or embedded in the outer tube, the electrically conducting material providing a main current path of the transducer, wherein current in the main current path inducing at least one torque in the flexible plate via the magnetic or magnetizable material.

2. A transducer for a mass flow meter, where the mass flow meter is arranged inside an outer tube working as a pressure containing part for the mass flow meter, the mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, the flexible plate provided with a magnetic or magnetizable material in predetermined positions, the transducer comprising: an electrically conducting material embedded in the tubular housing or embedded in the outer tube, the electrically conducting material providing a main current path of the transducer, wherein vibrations of the flexible plate inducing current in the main current path via the magnetic or magnetizable material, the transducer functioning as a pick-up for the mass flow meter.

3. Transducer system according to claim 1 or claim 2, wherein the ratio between the specific conductance of the electrically conducting material embedded in the tubular housing or embedded in the outer tube and the material of the outer tube is at least 8:1 , preferably 10:1 or most preferably 20:1 .

4. Transducer system according to one of claims 1-3, wherein the ratio between the specific conductance of the electrically conducting material embedded in the tubular housing or embedded in the outer tube and the material of the tubular housing is at least 8: 1 , preferably 10:1 or most preferably 20: 1 .

5. Transducer according to according to one of claims 1 -4, wherein the magnetic or magnetizable material is permanent magnets.

6. Transducer according to one of claims 1-5, wherein the current in the main current path is an oscillating current inducing an oscillating torque in the flexible plate.

7. Transducer according to one of claims 1 -6, further comprising at least one electrical conductor on the outside of the outer tube.

8. Transducer according to claim 1-7, wherein the current in the main current path is induced by an external coil.

9. Transducer according to one of claims 1 -8, further comprising at least one pair of electrical conductors on the outside of the outer tube.

10. Transducer according to one of claims 1 -9, further comprising at least one electrically conducting winding arranged on the outside of the outer tube.

11. Transducer according to one of claims 1-10, wherein the main current path further comprising at least one primary electrically conducting winding arranged on the outside of the outer tube, wherein the at least one primary electrically conducting winding passing through a core of a secondary coil arranged on the outside of the outer tube, wherein the core is preferably an iron core.

12. Transducer according to one of claims 1-11 , wherein the main current path further comprising a secondary electrically conducting winding arranged on the outside of the outer tube, the secondary electrically conducting winding passing through a common core of a primary coil.

13. Transducer according to claim 12, wherein the secondary electrically conducting winding is a single conductor, preferably an uninsulated conductor.

14. Transducer according to one of claims 11 , 12 or 13, wherein the primary coil and the secondary electrically conducting winding are wound around a common core.

15. Transducer according to one of claims 1-14, wherein the outer tube is provided with holes or with throughgoing openings in areas of the main current path.

16. Transducer according to one of claims 1-15, wherein the outer tube is made of a metal of low conductivity.

17. Transducer according to one of claims 1-16, wherein the outer tube is made of a magnetic material, a soft magnetic material, magnetic steel, carbon steel or nickel alloys.

18. Transducer according to one of claims 1-17, wherein the electrically conducting material is made of at least one of Cu, Ag, Au or Al (copper, silver, gold or aluminum).

19. Transducer according to one of claims 1-18, wherein the primary electrically conducting winding is made of at least one of Cu, Ag, Au or Al.

20. Transducer according to one of claims 1-19, wherein the secondary electrically conducting winding is made of at least one of Cu, Ag, Au or Al.21 . Transducer according to one of claims 1-20, wherein the tubular housing is made of a non-magnetic material.

22. Transducer according to one of claims 1-21 , wherein the tubular housing is made of a non-magnetic metal.

23. Transducer according to one of claims 1-22, wherein areas of magnetic material are embedded in the tubular housing.

24. Transducer according to one of claims 1 -23, wherein the tubular housing and the outer tube is bonded together by direct fusion, soldering, welding, diffusion welding or bracing.

25. Transducer according to one of claims 1-24, wherein the tubular housing and the electrically conducting material embedded in the tubular housing are bonded together by direct fusion, soldering, welding, diffusion welding or bracing.

26. Transducer according to one of claims 1-25, wherein the outer tube and the electrically conducting material embedded in the outer tube are bonded together by direct fusion, soldering, welding, diffusion welding or bracing.

27. Mass flow meter comprising at least one transducer according to at least one of claims 1-26.

28. Use of the transducer according to one of claims 1 -27, as an electromagnetic actuator for a sensor arranged inside an outer tube.

29. Use of the transducer according to one of claims 1 -28, as a pickup for a sensor arranged inside an outer tube.

30. Use of the transducer according to one of claims 1 -29 in a sensor for measuring mass flow of fluid of CO2 , NH3 , H2 or natural gas.31 . Use of the transducer according to one of claims 1 -30 in a sensor for high- pressure measurements of high-pressure fluids inside a pipe system.

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