Transducer

Abstract

A transducer for a mass flow meter. The mass flow meter has a tubular housing and a flexible plate able to vibrate in torsion. The flexible plate includes a magnetizable material. The transducer comprising at least one coil arranged on an outside of the tubular housing, and at least one magnet arranged on the outside of the tubular housing. The transducer may used as an electromagnetic actuator and / or pick-up for the mass flow meter. The sensor may e.g. be used for measuring mass flow of fluid of CO2, NHs, H2 or natural gas.

Description

[0001] TRANSDUCER

[0002] INTRODUCTION

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

[0004] BACKGROUND

[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. 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] US4,972,724 discloses a Coriolis mass flow meter with a straight measuring tube. The measuring tube is excited by an electromagnetic actuator arranged between the inlet and outlet of the measuring tube. The electromagnetic actuator is formed by electromagnet coils attached to the inner wall support pipe and cooperating permanent magnets attached to the outer surface of the measuring tube. The vibrations of the flow tube are detected by two electromagnetic sensors. The vibrations of the measuring tube are transversal oscillations. An electromagnetic sensor is composed of a permanent magnet attached to the exterior surface of the measuring tube and a cooperating pick-up coil attached to the inner surface of support pipe.

[0009] A further example of a Coriolis mass flow meter with two bent parallel measuring tube pairs adapted for zero-point adjustment is disclosed in US 2020 / 0319007A1 . The vibrations of the tubes are transversal oscillations. Inlet side and outlet side vibration sensors are provided for each measuring tube to detect the vibration of each tube. The vibration sensors are arranged on the outside of the measuring tube pairs. The vibration sensors comprising a magnetic part and a plunger coil part. The magnetic part and the plunger coil part must move relative to each other for the vibration sensor to detect the vibration of the tube.

[0010] 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.

[0011] US10393560B2, which is hereby incorporated by reference in its entirety, discloses a mass flow meter with a tubular housing, a flexible plate, an actuator, and at least two sensors. The tubular housing 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. The tubular housing has an inlet for a fluid flow, and an outlet for the fluid flow. The flexible plate has a width W. The flexible plate can be coupled to an interior wall of the tubular housing such that the flexible plate can vibrate in torsion. The actuator 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 can each be configured to measure oscillations of the flexible plate as a function of time at different locations. The mass flow meter can also include a computing device 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. 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. 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. There is a need for a sensor with high sensitivity and small pressure drops at high line pressures even for smaller sensors.

[0012] SUMMARY OF THE INVENTION

[0013] A transducer is provided. The transducer is adapted for a mass flow meter. The transducer may be used as an electromagnetic actuator for the mass flow meter. The transducer may be used as a pick-up for the mass flow meter.

[0014] In a first aspect it is disclosed a transducer for a mass flow meter. The mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, the at least one flexible plate comprising a magnetizable material. The transducer comprising at least one coil arranged on an outside of the tubular housing, and at least one magnet arranged on the outside of the tubular housing.

[0015] The transducer may further comprise at least one iron core arranged on the outside of the tubular housing. The at least one iron core may be arranged around or partly around the tubular housing. The at least one magnet may be arranged in the at least one iron core. The at least one iron core may pass through the at least one coil. At least a part of the at least one coil may be covered by the at least one iron core. The at least one core may be divided in at least two segments. The at least one core may be divided in at least two segments, wherein each segment is separated by the at least one magnet. The at least one magnet may be a static magnet, permanent magnet or electromagnet.

[0016] The flexible plate may comprise a number of segments. The flexible plate may comprise at least a first segment and at least a second segment, wherein the at least one first segment and the at least one second segment are made of different materials. The at least one flexible plate may comprise at least one of a ferromagnetic iron or a nickel-alloy material. The tubular housing may be made of a non-magnetic material or a non-magnetic metal.

[0017] In a further aspect it is disclosed a transducer assembly comprising at least two transducers according above. The transducer assembly may further include at least two core segments defining a ring structure or a part of a ring structure; the at least one magnet arranged between the at least two core segments. The at least one coil may be wound around a core segment. At least a part of the at least one coil may be arranged on the inside of the core segment or embedded in the core segment. The ring structure or the part of the ring structure may be circumferentially arranged around the outside of the tubular housing.

[0018] It is in a further aspect disclosed a mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, the at least one flexible plate comprising a magnetizable material. The mass flow meter comprising at least one transducer according to above. The at least one flexible plate may extend along at least a part of the tubular housing and be at least partially coupled to an interior wall of the tubular housing at opposed longitudinal ends of the flexible plate such that the flexible plate is able to vibrate in torsion.

[0019] In a further aspect it is disclosed a mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, wherein the at least one flexible plate extending along at least a part of the tubular housing and at least partially coupled to an interior wall of the tubular housing at opposed longitudinal ends of the flexible plate such that the flexible plate is able to vibrate in torsion, the at least one flexible plate comprising a magnetizable material, the mass flow meter comprising at least one transducer, wherein each transducer comprising

[0020] - at least one coil arranged on an outside of the tubular housing, and

[0021] - at least one magnet arranged on the outside of the tubular housing.

[0022] In a further aspect it is disclosed a mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, wherein the at least one flexible plate extending along at least a part of the tubular housing and at least partially coupled to an interior wall of the tubular housing at opposed longitudinal ends of the flexible plate such that the flexible plate is able to vibrate in torsion, the at least one flexible plate comprising a magnetizable material, the mass flow meter comprising at least one transducer assembly according to above. The transducer or transducer assembly may be used as an electromagnetic actuator for a mass flow meter. The transducer may be used as a pickup for a mass flow meter. The transducer may be used in a sensor for measuring mass flow of fluid of CO2 , NH3 , H2 or natural gas.

[0023] The sensor enables high sensitivity and small pressure drops at high line pressures even for smaller sensors.

[0024] The transducer avoids use of permanent magnets in the flexible plate. This enables production of a flexible plate with small dimensions. E.g. the sensor may be adapted to pipelines / tubes with an internal diameter of e.g. 10mm. The flexible plate may be thin and made in one piece. When the dimensions are small, it may also be challenging to manufacture the flexible plate with permanent magnets in the flexible plate. There is also more available space for components on the outside of the tubular housing in particular for sensors with small dimensions.

[0025] The transducer design also avoids having permanent magnets arranged on the inside of the tubular housing. The flow to be measured flows through the tubular housing. Permanent magnets are sensitive to corrosion and must be encapsulated to avoid exposure to the fluid flow. Permanent magnets are vulnerable to corrosion, e.g. Neodymium magnets are particularly vulnerable. The components inside the tubular housing are exposed to the fluid flow. Permanent magnets in the flexible plate must be covered and sealed to avoid exposure to the fluid flow. This may be difficult to achieve in particular for sensors for small pipes / tubes. Arranging the magnets on the outside of the tubular housing avoids exposure to the fluid flow and solves the problem with corrosion for permanent magnets. Arranging the magnets on the outside of the tubular housing also enables a simpler construction which is easier and more cost effective to produce. The production costs of the transducer and mass flow meter are considerably reduced. The flexible plate does not need any permanent magnets. Cavities for embedding the permanent magnets may also be avoided. This also reduce the production costs. The transducer does not require the coil and / or the magnet on the outside of the tubular housing to move. The coil and magnet on the outside of the tubular housing do not move in order to detect the vibrations of the flexible plate or induce a torque in the flexible plate. This simplifies the construction and also reduces the production costs.

[0026] The magnetizable material of the flexible plate is magnetized by either an external permanent magnet or an external electromagnet. The external permanent magnet or the external electromagnet are arranged on the outside of the tubular housing. The magnetizable material is not a permanent magnet. The magnetizable material is magnetized as long as the permanent magnet is present or as long as current is supplied to the external electromagnet. Some magnetizable materials may however due to hysteresis experience some residual magnetism after the electromagnetic field is turned off. This is however a temporary effect.

[0027] A transducer with an electromagnet on the outside of the tubular housing may also be turned off providing a non-magnetic transducer. This enables cleaning of the transducer. Dirt or particles may attach to the transducer when in use, and this dirt and particles may come loose when the transducer is no longer magnetic. In this way, the sensor may be self-cleaning.

[0028] The transducer design enables production of small transducers and small sensor. Small transducers may have about 10 mm of internal diameter of the tubular housing. The flexible plate may be thin as there may no cavities and no embedded permanent magnets. The flexible plate may also be made of segments, where only the part of the flexible plate in the areas for the transducers may be made of a magnetizable material. This saves costs, as magnetizable materials are expensive. E.g. Nickel is very expensive. The use of magnetizable material may be further reduced if the magnetizable material is arranged in longitudinal stripes on the flexible plate. The rest of the flexible plate may be made of an inexpensive non-magnetic material or non-magnetic metal. The sensor and transducer may in some embodiments be designed to not require any welding, lids or seals. BRIEF DESCRIPTION OF DRAWINGS

[0029] Example embodiments are described with reference to the following drawings. The example embodiments are only examples and not limiting for the invention.

[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 groups of magnets or magnetizable material arranged on the flexible plate.

[0033] Figure 2 is perspective view illustrating an exemplary embodiment of a mass flow meter with a flexible plate arranged inside a tubular housing and with external coils arranged around the tubular housing forming a part of exemplary transducers. The flexible plate is provided with a magnetizable material. The transducers include external magnets arranged on the outside of the tubular housing.

[0034] Figure 3 is perspective view illustrating a further exemplary embodiment of Figure 2, where the flexible plate has segments of magnetizable material. Figure 4 is perspective view illustrating an exemplary embodiment of a mass flow meter with a flexible plate arranged inside a tubular housing and with four exemplary external coils arranged around the tubular housing forming a part of exemplary transducers. The flexible plate is provided with a magnetizable material. The transducers include external magnets arranged on the outside of the tubular housing.

[0035] Figure 5 illustrates in cross-section an exemplary embodiment of a mass flow meter with a flexible plate arranged inside a tubular housing and with exemplary transducers with magnets arranged on the outside of the tubular housing. The flexible plate is provided with a magnetizable material. Four external coils are arranged on the outside of the tubular housing. The external coils may be as illustrated in Figure 4.

[0036] Figure 6 illustrates in cross-section an exemplary embodiment of a mass flow meter with a flexible plate arranged inside a tubular housing and with an exemplary transducer with magnets arranged on the outside of the tubular housing. Four exemplary coils are arranged on the outside of the tubular housing inside an iron core. The external coils may be as illustrated in Figures 2 and 3.

[0037] Figure 7 illustrates in cross-section an exemplary embodiment of a mass flow meter with a flexible plate arranged inside a tubular housing and with an exemplary transducer with magnets arranged on the outside of the tubular housing. The flexible plate is provided with a magnetizable material. Exemplary iron core segments are arranged on the outside of the tubular housing. The external coils may be as illustrated in Figure 4.

[0038] Figure 8 illustrates in cross-section an exemplary embodiment of a mass flow meter with a flexible plate arranged inside a tubular housing and with an exemplary transducer with magnets arranged on the outside of the tubular housing. The flexible plate is made of a non-magnetic material or non-magnetic metal. A magnetizable material is embedded in the flexible plate. 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.

[0039] DETAILED DESCRIPTION

[0040] Example embodiments are described with reference to the drawings. The drawings are illustrations for understanding of the principles of the disclosed mass flow meter concerning e.g. the construction, function, manufacture and use of the mass flow meter and its different parts. The drawings are not necessarily to scale. The example embodiments are not limiting for this disclosure. Other exemplary embodiments may be envisaged.

[0041] A mass flowmeter with a fluid channel (e.g., a pipe or pipeline) containing a flowing fluid and a mass flow meter at least partially coupled thereto at respective ends. The mass flow meter has a tubular housing and a flexible plate configured to vibrate in torsion such that measurement of the movement of the flexible plate can be related to mass flow of the flowing fluid. Mass flow can be measured directly by the mass flow meter regardless of the geometry of the tubular housing. The mass flowmeter is provided with one actuator positioned on a surface of the tubular housing in a longitudinal center of the tubular housing. The actuator is configured to apply an oscillating torque to the flexible plate sufficient to vibrate the flexible plate in torsion. The frequency of the actuator may be set to a resonance frequency of the flexible plate. Two sensors are arranged symmetrically about the longitudinal center of the tubular housing to measure a plurality of oscillations of the flexible plate as a function of time at these two locations arising from the applied oscillating torque.

[0042] The longitudinal axis A of the flexible plate is parallel to the x-axis of the mass flow meter. Forces FA , -FA applied by the actuator may have opposite directions parallel to the y-axis. The forces may act along the width, partly or whole width, of the flexible plate. The applied forces FA , -FA is varied in magnitude and direction to provide an oscillating torque exciting the flexible plate to vibrate in a torsional mode. The resulting Coriolis forces -Fc, Fc acting on the flexible plate provides a torsional vibration with an angular velocity Qyand Qy. Fig. 1 A and 1 B illustrate exemplary embodiments of a mass flow meter with a tubular housing 350. 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 350 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 tubular housing 350 may be substantially straight between the housing inlet and the housing outlet. The surfaces of the tubular housing in contact with the fluid flow may be rounded and smooth to avoid unnecessary friction disturbing the fluid flow.

[0043] The tubular housing 350 may take other geometric forms depending e.g. on the fluid channel (e.g. pipeline) and the fluid flow to be monitored, as well as other circumstances as e.g. temperature and / or pressure of the surroundings, temperature and / or pressure of the fluid flow, the material of the fluid channel, and the tubular housing. The geometry and / or materials of the tubular housing may be approximately the same as that of the fluid channel. The tubular housing may be formed from any suitable materials including, for example, polymers, ceramics, metals, and metal alloys (e.g., steels, copper and copper alloys, aluminium and aluminium alloys, etc.).

[0044] The mass flow meter may be integrally formed with the fluid channel. The entire fluid flow Vx351 passes through the mass flow meter. An inlet and an outlet of the mass flow meter housing may form a fluid-tight coupling with the fluid channel or pipeline pumps, dispensers, etc. of the fluid flow system. Examples of fluid-tight couplings can include, but are not limited to, threaded engagements, clamps, welds, and the like.

[0045] 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.

[0046] 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).

[0047] When the flexible plate is excited and vibrates in a torsional mode and interacts with the fluid flow to be measured, a phase shift will occur between the oscillations in two different positions of the flexible plate. The mass of the flowing fluid effects the excitation of the flexible plate and causes a delay of the excitation or wave travelling along the flexible plate. This delay may be viewed as some sort of Doppler effect when travelling along the flexible plate in the longitudinal direction. The phase shift is approximately proportional to the mass flow of the fluid flow. The sensors may therefore be arranged a distance apart to provide a sufficiently long travel length for the fluid flow along the flexible plate before detection by the second sensor. A direct measurement of mass flow of the fluid may be achieved by determining the proportionality constant of the mass flow meter. Estimation of the mass flow of fluid may then be performed by a computing device receiving sensor signals from the sensor system.

[0048] 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 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).

[0049] 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. As any gap between the wall of the cavity 353 and the flexible plate 352 is small this does not allow a significant amount of the fluid Vxto pass between opposite edges of the flexible plate 352 (e.g., vertically in FIG. 1 B). As the gap is small, the flexible plate interacts with substantially the entire fluid flow passing through the tubular housing. In some embodiments, the flexible plate may have a curved shape in an equilibrium or unfixed state (not shown). The flexible plate may in some embodiments be extended / stretched and provided with a tension when attached inside the tubular housing, to change the resonance frequency of the flexible plate.

[0050] 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 may include two actuators 302, 303 as illustrated in Fig.lA and 1 B. As shown in FIG. 1 A and 1 B, the two actuators are to be positioned outside the tubular housing 350. Positioning outside the tubular housing may e.g. involve on the surface of the tubular housing, or adjacent to the outer surface of the tubular housing. 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.

[0051] 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.1 A-1 B 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, which will be described later. These positions may however somewhat vary depending on the accurate geometry.

[0052] 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.

[0053] The coils may be connected to a controller 300 or e.g. computing device for controlling the current supplied to the coils generating the magnetic field to apply an oscillating torque to the flexible plate at a selected frequency. At least one of the magnitude, frequency and / or phase of the current applied to the coils 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 coils may be configured to receive feedback e.g. from a sensor system to drive the flexible plate at resonance.

[0054] As mentioned, the mass flow meter 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 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. The pick-up sensors may e.g. be based on the Hall effect or may be magnetic pick-up sensors. The electromagnetic sensors may also in some embodiments be the actuating system itself. The electromagnetic actuating system may then 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 mass sensor. The sensor system may be connected to a computing device or controller or other device receiving sensor signals from the sensor system. The computer device, controller or other device may also control the sensor system.

[0055] 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. These positions may however somewhat vary depending on the accurate geometry. 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.

[0056] The flexible plate may be provided with a number of vanes. The number of vanes may be two, three, four or higher number of vanes as e.g. eight or more. The angle between the vanes can be varied. In an exemplary embodiment with four vanes, the angle between each vane is 90 ° or about 90°. The vanes extend radially outward at about 90° with respect to one another. In an exemplary embodiment with eight vanes, the angel between each vane is 45° or about 45°. The vanes can possess approximately equal width. The number of vanes and the angle between the vanes may vary depending on the characteristics of the fluid flow to be measured and other factors as the environment and surroundings of the fluid flow. The vanes increase the stiffness of the flexible plate and avoids bending of the flexible plate without increasing the torsional stiffness of the flexible plate. The mass sensor is based on applying oscillating torques to the flexible plate to vibrate the flexible plate in harmonic oscillations and a high sensitivity for torsion increases the flexible plate’s sensitivity for viscosity of the fluid flow. E.g. for mass measurement of a low density fluid flow such as liquid gas e.g. H2, or a high density liquid at high density such as e.g. CO2, the torsional stiffness should be low to be able to measure the mass flow of H2 and CO2 with a sufficiently high sensitivity.

[0057] Fig.1 C illustrates an embodiment where an actuator system 305 is arranged in an area about a longitudinal center of the flexible plate in positions A1 and A2. The sensor systems 301 , 304 may be the same sensor systems as in Fig.1 A and 1 B. The actuator system covers an area of the flexible plate. The actuator system in Fig.1 B may be provided by an electromagnetic actuating system. The coils may be arranged at a distance sufficiently apart from each other to be able to apply at least two oscillating torques to the flexible plate to vibrate the flexible plate with the permanent magnets in torsion. The net sum of the oscillating torques applied to the flexible plate may be zero or substantially zero. By using two coils, 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 embodiment in Fig.1 C may vibrate the flexible plate in a 1stharmonic oscillation.

[0058] A transducer for a mass flow meter is disclosed. The mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, the at least one flexible plate comprising a magnetizable material. The transducer includes at least one coil arranged on an outside of the tubular housing, and at least one magnet arranged on the outside of the tubular housing. Figures 2-8 illustrates exemplary embodiments of a transducer for a mass flow meter. The mass flow meter comprising a tubular housing and a flexible plate able to vibrate in torsion as explained above.

[0059] Figure 2 is perspective view illustrating an exemplary embodiment of a transducer for a mass flow meter. The mass flow meter has a flexible plate 103 arranged inside a tubular housing 102. The flexible plate is able to vibrate in torsion. The tubular housing extending along a longitudinal axis and configured to receive a flow of fluid therethrough. The flexible plate extending along at least a part of the tubular housing and is at least partially coupled to an interior wall of the tubular housing at opposed longitudinal ends of the flexible plate such that the flexible plate is able to vibrate in torsion. The flexible plate has four vanes. The flexible plate is provided with a magnetizable material. The magnetizable material may is provided in each of the vanes. Transducers are arranged on the outside of the tubular housing. Each transducer includes a coil. In Figure 2 four transducers are arranged around the circumference of the tubular housing. In Figure 2, the four coils 108 of the four transducers are arranged around the tubular housing 102 forming a coil arrangement. The coil arrangement is circumferentially arranged around the tubular housing. The coils may be connected. In Figure 2, the coils are connected on the short side of the coils. In Figure 2, the coils are arranged around the circumference of the tubular housing such that the coils are positioned in an area between the vanes. The coil arrangement is a part of the transducers for the mass flow meter. The transducer includes at least one magnet (not shown) arranged on the outside of the tubular housing. The transducer may also include an iron core (not shown) arranged on the outside of the tubular housing. The transducers may function as an actuator or as a pick-up for the mass flow meter. The transducers may be configured to apply at least two oscillating torques to the flexible plate sufficient to vibrate the flexible plate in torsion. The coils may be connected to a e.g. a power supply or controller or e.g. computing device for controlling the current supplied to the coils modifying an existing magnetic field to apply an oscillating torque to the flexible plate at a selected frequency. The existing magnetic field is provided by external permanent magnet(s)) or external electromagnet(s). Current in the coil arrangement 108 may induce at least one torque in the flexible plate via the magnetizable material. The transducer may be configured to measure oscillations of the flexible plate as a function of time. The transducer functioning as a pick-up for the mass flow meter. Vibrations of the flexible plate may induce current in the coil arrangement 108 via the magnetizable material 104. The magnetizable material of the flexible plate is not a permanent magnet.

[0060] Figure 3 is perspective view illustrating an exemplary embodiment of a mass flow meter with a flexible plate 103 arranged inside a tubular housing 102. Four transducers 108 are arranged on the outside of the tubular housing. The tubular housing extending along a longitudinal axis and configured to receive a flow of fluid therethrough. The flexible plate 103 extending along at least a part of the tubular housing and is at least partially coupled to an interior wall of the tubular housing at opposed longitudinal ends of the flexible plate such that the flexible plate is able to vibrate in torsion. The flexible plate is provided with a magnetizable material 104. Transducers are provided for the mass flow meter. A transducer includes a coil arranged on the outside of the tubular housing. The coil in Figure 3 is an external coil as in Figure 2. Also in Figure 3, four coils are arranged on the outside of the tubular housing. The four coils are electrically connected at the short sides forming a coil arrangement. The coil arrangement is circumferentially arranged around the tubular housing. A transducer includes at least one magnet (not shown) arranged on the outside of the tubular housing. The transducers may also include an iron core (not shown) arranged on the outside of the tubular housing. The flexible plate is provided with a magnetizable material 104. The difference from the exemplary embodiment in Figure 2, is that the exemplary embodiment in Figure 3 has a flexible plate formed by a number of segments. The segments may be made of different materials. In Figure 3, the magnetizable material 104 form a segment of the flexible plate 103. The coil arrangement is arranged around the tubular housing in a position above the magnetizable material 104. The coil arrangement encloses the magnetizable material 104 in the flexible plate. The transducer may function as an actuator or as a pick-up for the mass flow meter as explained above. Figure 4 is a perspective view illustrating an exemplary embodiment of a mass flow meter with a flexible plate arranged inside a tubular housing. The tubular housing extending along a longitudinal axis and configured to receive a flow of fluid therethrough. The flexible plate 103 extending along at least a part of the tubular housing and is at least partially coupled to an interior wall of the tubular housing at opposed longitudinal ends of the flexible plate such that the flexible plate is able to vibrate in torsion. The flexible plate is provided with a magnetizable material 104. Four transducers 108 (only three are shown) are provided for the mass flow meter. Each transducer includes a coil arranged on the outside of the tubular housing. Each transducer includes at least one magnet (not shown) arranged on the outside of the tubular housing. Each transducer may also include an iron core (not shown) arranged on the outside of the tubular housing. Four external coils, each representing a transducer, are arranged around the tubular housing. The coils are arranged extending outwards from the external surface of the tubular housing. Each coil has a rectangular shape with two long sides and two short sides. The first long side facing down towards the external surface of the tubular housing. The two short sides extending upwards from the external surface of the tubular housing and connecting the long side away from the external surface of tubular housing. The first long side functions as a main current path inducing at least one torque in the flexible plate via the magnetizable material 104 in the flexible plate. The coils are arranged above an end surface of each of the vanes of the flexible plate. This provides magnetic field lines at about 90 degrees on each of the vanes. The transducers are configured to apply at least two oscillating torques to the flexible plate sufficient to vibrate the flexible plate in torsion.

[0061] A net sum of the at least two oscillating torques applied to the flexible plate 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 four oscillating torques the sum of all the oscillating torques should be zero or substantially zero. Vibrations of the flexible plate may induce current in the coils via the magnetic or magnetizable material, the transducer functioning as a pick-up for the mass flow meter. Figure 5 illustrates in cross-section an exemplary embodiment of a mass flow meter with a flexible plate 103 arranged inside a tubular housing. The flexible plate is provided with a magnetizable material 104. Four external coils 108 are arranged on the outside of the tubular housing 102. The arrangement of the four external coils on the outside of the tubular housing correspond to the coil arrangement illustrated in Figure 4. Four core 111 segments, preferably of iron, are also arranged on the outside of the tubular housing. The four core segments forming a ring structure. The ring structure is circumferentially arranged around the tubular housing. Four magnets 107 are arranged on the outside of the tubular housing. The magnets 107 are arranged between each core segment. In the embodiment in Figure 5, the magnets are arranged in positions between the vanes of the flexible plate. The position of a magnet is about 45° with respect to a vane in Figure 5. The magnets may however also be positioned in other positions in the ring structure provided by the iron core segments and the magnets. The four external coils have a shape as illustrated in Figure 4. The arrangement of the four coils directly above each vane of the flexible plate is clearly seen in Figure 5. The part of the coil facing the tubular housing is arranged close to the external surface of the tubular housing to be as close as possible to the flexible plate. This ensures an efficient use of the magnetic field force acting on the flexible plate from the coil. It is desirable to gather the magnetic field lines in the magnetizable flexible plate. The magnetic field lines in the magnetizable flexible plate return via the coil return path. The embodiment provides closed magnetic field lines. An external coil, a core segment and a magnet represent a transducer. The four transducers form a transducer assembly.

[0062] The coil 108 may be wound around the core 111. The core segments, with the coils wound around the core, and the magnets form a ring that is arranged around the tubular housing. The iron core passes through the coil. The ring may be fixed in place on the tubular housing e.g. by glue, welding, screws or bolts. The transducers must be held in place in the desired position on the tubular housing during use. In a typical mass sensor design, there may be two transducer assemblies functioning as actuators and one transducer assembly functioning as a pick-up. The positions of the transducer assemblies on the tubular housing of the mass flow meter have a common reference. The common reference is defined in view of the point where the end of the flexible plate is attached to the mass sensor. The torques exerted on the flexible plate by the two actuators must have a net sum of zero. The embodiment for the transducer assembly in Figure 5 may form a quadrupole. The poles of oppositely arranged magnets are facing towards each other. Magnets arranged next to each other around the circumference of the tubular housing are arranged with their poles facing in opposite directions. (North, South, North, South).

[0063] Figure 6 illustrates in cross-section an exemplary embodiment of a mass flow meter with a flexible plate 103 arranged inside a tubular housing. The flexible plate is provided with a magnetizable material 104. Four transducers with magnets 107 and coils 108 are arranged on the outside of the tubular housing. Four core 111 segments, preferably of iron, are also arranged on the outside of the tubular housing. The four core segments forming a ring structure. The ring structure is circumferentially arranged around the tubular housing. The arrangement and positioning of the magnets and the iron core segments correspond to the embodiment in Figure 5. In Figure 6, the four coils are however arranged on the inside of the iron core segments. The coils in Figure 6 correspond to the coil arrangement illustrated in the embodiment in Figures 2 and 3. The part of the coil providing a main current path for inducing a magnetic force in the flexible plate is covered by the iron core. The part of the coil functioning as a return path for the magnetic field lines, may be arranged in the iron core or be on the outside of the iron core.

[0064] Figure 7 illustrates in cross-section an exemplary embodiment of a mass flow meter with a flexible plate 103 arranged inside a tubular housing 102. The flexible plate is provided with a magnetizable material 104. Four external coils 108 are arranged on the outside of the tubular housing 102. Four core segments 111 , preferably of iron, are also arranged on the outside of the tubular housing. Two magnets 107 are arranged on the outside of the tubular housing. The magnets 107 are arranged between each core segment. Two core segments 111 together with a magnet 107 form a first segment and a second segment respectively. The first and second core segments are circumferentially arranged around a part of the outside of the tubular housing. The first and second core segments are arranged opposite of each other. The iron core with magnets does not form a continuous core around the tubular housing as in Figures 5 and 6. In the embodiment in Figure 7, the two magnets are arranged in positions between the vanes of the flexible plate. The position of a magnet is about 45° with respect to a vane in Figure 7. The four external coils have a shape as illustrated in Figure 4. The arrangement of the four coils directly above each vane of the flexible plate is clearly seen in Figure 7. The embodiment in Figure 7 may provide a bi-pole configuration of the four transducers. The magnets may be arranged with their North poles in the same direction facing either inward towards the center of the tubular housing or outwards away from the tubular housing.

[0065] Figure 8 illustrates in cross-section an exemplary embodiment of a mass flow meter with a flexible plate arranged inside a tubular housing and with exemplary transducers with magnets arranged on the outside of the tubular housing. I the embodiment in Figure 8, the flexible plate is made of a non-magnetic material or non-magnetic metal. A magnetizable material is embedded in the flexible plate. The configuration and arrangement of the four coils 108, four magnets 107 and four iron cores 111 corresponds to the embodiment illustrated in Figure 5. The embodiment in Figure 8 with embedded magnetizable material in the flexible plate may be used in certain embodiments for medium and larger mass flow meters. The magnetizable material is costly. By embedding the magnetizable material in areas of the flexible plate in positions corresponding to the positions of the transducers, the use of costly magnetizable material is considerably reduced.

[0066] The magnetizable material of the flexible plate should be a material of high relative permeability; e.g. ferromagnetic iron or a nickel-alloy material. Non-limiting examples are Supermalloy, Permalloy, p metal, ferritic steel, Martensitic stainless steel and Austenitic stainless steel. The materials (except ferritic steel) also have a fair resistance against corrosion. Corrosion resistance is important when the fluid is corrosive as the flexible plate inside the tubular housing is exposed to the fluid flow. The tubular housing may be made of a non-magnetic material or a nonmagnetic metal. The magnetizable material of the flexible plate is not a permanent magnet. The magnetizable material of the flexible plate is magnetized by an external electromagnet or permanent magnet) outside of the tubular housing. The magnetizable material is magnetized as long as current is supplied to the electromagnet or the permanent magnet is present. Some magnetizable materials may, due to hysteresis in the material, experience some residual magnetism after the electromagnetic field is turned off as a temporary effect. The magnetizable material is not a permanent magnet in any of the exemplary embodiments of the transducer in this disclosure.

[0067] The magnetizable material in the flexible plate is magnetized by external electromagnet(s) or permanent magnet(s). Permanent magnets have a constant magnetization. The magnetic field experienced by the magnetizable material in the flexible plate is a sum of the magnetic field from the permanent magnet(s), the magnetic field from the electromagnet(s) and the magnetic field from the coil(s). The electromagnet(s) may be driven by a DC current, but an AC current is also possible. If AC current is used, the oscillating frequency of the flexible plate must not be the same as the frequency of the AC current. The actuator may be driven by an AC current following the resonance frequency of the flexible plate. A phase- looked loop may be used to drive the actuator in phase with the oscillations in the flexible plate. Use of AC current supply to the electromagnets(s) may be more usable for the pick-up.

[0068] For an actuator a constant magnetic field is provided by the permanent magnet(s) or the electromagnet(s) driven by a DC current. A current is supplied to the coil of the transducer for generating the torque in the flexible plate. The magnetic field from the coil is in addition to the magnetic field from the permanent magnet or electromagnet. The magnetic field has accordingly a DC component and an oscillating superimposed component. When the transducer is functioning as an actuator, the magnetic field from the coil are superimposed on top of the magnetic field from the permanent magnet or electromagnet. The sum of these magnetic fields results in the torque driving the flexible plate in torsional oscillations. The actuator is driving the flexible plate wirelessly through the tubular housing. This is also the case even if the tubular housing is made of electrically conducting metal. An electromagnet for a pick-up may be driven by an AC current. The signal from the pick-up would then be a mix of the frequency (or frequencies) of the AC current and the frequency (or frequencies) of the oscillator (the flexible plate). When the transducer is functioning as a pick-up, there is no magnetic field from the coil. The oscillation of the flexible plate will however provide a time variation on top of the permanent magnetic field from the permanent magnets. This time varying magnetic field will induce a voltage in the coil. The voltage in the coil is detected. The pick-up is sensing the oscillations of the flexible plate wirelessly through the tubular housing. This is also the case even if the tubular housing is made of electrically conducting metal.

[0069] The signals from the transducer may be received via a signal amplifier / instrumentation amplifier before being input into an analog to digital converter. The input impedance should be high (giga ohm) in order for the amplifier to not (or as little as possible) put a load on the coil as this would mean that energy is drained from the oscillations of the flexible plate.

[0070] The magnets arranged on the outside of the tubular housing may e.g. be static magnets, permanent magnets or electromagnets. The electromagnets may be fed with DC current. The electromagnets may be turned off when the sensor is not in use. When the electromagnets are turned off, dirt or particles accumulated on the sensor during use may loosen, enabling a self-cleaning sensor.

[0071] The transducer and transducer assembly have no moving parts. The transducer and transducer assembly are fixed in position on the outside of the tubular housing. The transducers and transducer assemblies may be arranged in positions on the outside of the tubular housing as explained for Figure 1 A-1 C.

[0072] The mass flow meter may be used for measuring mass flow of e.g. CO2, NH3 , and H2 or LNG or other gas flows at high pressures.

[0073] 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, wherein the mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, the at least one flexible plate comprising a magnetizable material, the transducer comprising:- at least one coil arranged on an outside of the tubular housing, and- at least one magnet arranged on the outside of the tubular housing.

2. Transducer according to claim 1 , further comprising at least one iron core arranged on the outside of the tubular housing.

3. Transducer according to one of claims 1-2, wherein the at least one iron core is arranged around or partly around the tubular housing.

4. Transducer according to one of claims 1-3, wherein the at least one magnet is arranged in the at least one iron core.

5. Transducer according to one of claims 1-4, wherein the at least one iron core passes through the at least one coil.

6. Transducer according to one of claims 1 -4, wherein at least a part of the at least one coil is covered by the at least one iron core.

7. Transducer according to one of claims 1-3, wherein the at least one core is divided in at least two segments.

8. Transducer according to one of claims 1-3, wherein the at least one core is divided in at least two segments, wherein each segment is separated by the at least one magnet.

9. Transducer according to one of claims 1-8, wherein the at least one magnet is a static magnet, permanent magnet or electromagnet.

10. Transducer according to one of claims 1-19, wherein the flexible plate comprising a number of segments.11 . Transducer according to one of claims 1-10, wherein the flexible plate comprising at least a first segment and at least a second segment, wherein the at least one first segment and the at least one second segment are made of different materials.

12. Transducer according to one of claims 1-11 , wherein the at least one flexible plate comprising at least one of a ferromagnetic iron or a nickel-alloy material.

13. Transducer according to one of claims 1-12, wherein the tubular housing is made of a non-magnetic material or a non-magnetic metal.

14. A transducer assembly comprising at least two transducers according to at least one of claims 1 -13.

15. Transducer assembly according to claim 14, further comprising:- at least two core segments defining a ring structure or a part of a ring structure;- the at least one magnet arranged between the at least two core segments.

16. Transducer assembly according to claim 15, wherein the at least one coil is wound around a core segment.

17. Transducer assembly according to claim 16, wherein at least a part of the at least one coil is arranged on the inside of the core segment or embedded in the core segment.

18. Transducer assembly according to one of claims 15-17, wherein the ring structure or the part of the ring structure are circumferentially arranged around the outside of the tubular housing.

19. Mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, the at least one flexible plate comprising a magnetizable material, the mass flow meter comprising at least one transducer according to at least one of claims 1 -13.

20. Mass flow meter according to claim 19, wherein the at least one flexible plate extending along at least a part of the tubular housing and at least partially coupled to an interior wall of the tubular housing at opposed longitudinal ends of the flexible plate such that the flexible plate is able to vibrate in torsion.21 . Mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, wherein the at least one flexible plate extending along at least a part of the tubular housing and at least partially coupled to an interior wall of the tubular housing at opposed longitudinal ends of the flexible plate such that the flexible plate is able to vibrate in torsion, the at least one flexible plate comprising a magnetizable material, the mass flow meter comprising at least one transducer, wherein each transducer comprising- at least one coil arranged on an outside of the tubular housing, and- at least one magnet arranged on the outside of the tubular housing.

22. Mass flow meter comprising a tubular housing and at least one flexible plate able to vibrate in torsion, wherein the at least one flexible plate extending along at least a part of the tubular housing and at least partially coupled to an interior wall of the tubular housing at opposed longitudinal ends of the flexible plate such that the flexible plate is able to vibrate in torsion, the at least one flexible plate comprising a magnetizable material, the mass flow meter comprising at least one transducer assembly according to claim 14.

23. Use of the transducer according to one of claims 1 -13 or the transducer assembly according to one of claims 14-18, as an electromagnetic actuator for a mass flow meter.

24. Use of the transducer according to one of claims 1 -13 or the transducer assembly according to one of claims 14-18, as a pickup for a mass flow meter.

25. Use of the transducer according to one of claims 1 -13 or the transducer assembly according to one of claims 14-18 in a sensor for measuring mass flow of fluid of CO2 , NH3 , H2 or natural gas.

Images