Coriolis flow meter with a vibration-type sensor and use of the Coriolis flow meter

Abstract

Coriolis flowmeter (1) comprising a vibration-type sensor for measuring a flow rate and / or flow velocity of a fluid medium carried in a pipeline, wherein the sensor comprises a vibrating tube (2), and at least one electrodynamic exciter (3.II) for exciting the vibrating tube (2) into a oscillating motion and at least one electrodynamic sensor (3.I or 3.III), in particular two sensors (3.I and 3.III), for detecting a measurement signal generated by vibrations of the tube (2), wherein the exciter (3.II) and / or the sensor (3.I or 3.III)III) comprises at least two components, wherein a first component is designed as a printed circuit board (7, 17) with at least one conductor track (9, 19) for forming a printed circuit board coil, wherein a second component is designed as a magnetic field generating element (6), wherein one of the two components is arranged directly or indirectly on or in the vibrating tube (2) and excites the tube (2) to vibrate or receives the measurement signal by relative movement to the second of the two components, characterized in that at least one turn, preferably all turns, of the conductor track (9, 19) has an area of ​​less than 3000 µm. 2 / turn, preferably smaller than 1500 µm² / turn.

Description

[0001] The invention relates to a Coriolis flowmeter with a vibration-type sensor according to the preamble of claim 1 and a use of the Coriolis flowmeter according to claim 9.

[0002] Field devices for process measurement technology with a vibration-type sensor, and especially Coriolis flowmeters, have been known for many years. The basic design of such a measuring device is described, for example, in EP 1 807 681 A1, and the design of a generic field device within the scope of the present invention is fully incorporated herein by reference. This measurement technology and corresponding measuring devices have also been extensively described by the applicant in numerous other patent applications. An example of a field device for process measurement technology is a Coriolis flowmeter.

[0003] Coriolis flowmeters typically have at least one or more vibrating tubes that can be set into vibration by means of an exciter. These vibrations are transmitted along the length of the tube and vary depending on the type of fluid in the tube and its flow velocity. A sensor, or in particular two spaced-apart sensors, can detect the varying vibrations at another point in the tube as a measurement signal or signals. An evaluation unit can then determine the flow rate from the measurement signal(s).

[0004] Corresponding exciters and / or sensors are mostly based on an electrodynamic principle and are usually multi-part, comprising a magnet-generating unit for producing a magnetic field and a coil through which this magnetic field passes. This coil typically consists of wire wound onto a coil former, usually a cylindrical one. This technology has generally proven its worth.

[0005] An alternative coil solution is disclosed in US Patent 5,349,872 A.

[0006] However, there are applications, e.g., applications at medium temperatures above 250°C, in which a Coriolis flow meter is used, which place particularly high demands on the sensor and excitation design and where a high winding density of the coils with good insulation of the conductor tracks between them is required.

[0007] Based on the above explanation, the object of the present invention is now to solve the aforementioned problem.

[0008] The invention solves this problem by means of a Coriolis flow meter with the features of claim 1.

[0009] A Coriolis flow meter according to the invention comprises a vibration-type sensor for measuring a flowable medium conveyed in a pipeline. Such a medium can be, for example, a liquid, a gas, a flowable sludge, or the like.

[0010] The sensor comprises a vibrating tube and at least one electrodynamic exciter capable of setting the tube into oscillation. For this purpose, the exciter typically receives an excitation signal, which causes it to vibrate and then transmits these vibrations to the tube.

[0011] Furthermore, the measuring device has at least one sensor, in particular two sensors, which can record or detect a measurement signal generated by vibrations of the pipe. These vibrations vary with the type of fluid in the pipe and with its flow velocity.

[0012] According to the invention, the exciter and / or the sensor comprises at least two components, wherein a first component is designed as a printed circuit board with at least one conductor track for forming a printed circuit board coil and wherein a second component is designed as a magnetic field generating element, e.g. with one or more permanent magnets and / or electromagnets.

[0013] One of the two components is arranged on or inside the vibrating tube and, through relative movement to the second component, causes the tube to vibrate or records a measurement signal based on this relative movement. The component can be arranged directly or indirectly on the vibrating tube, for example, by means of a spacer.

[0014] By designing the first component as a printed circuit board with a conductor track, it is possible, compared to a conventional wound coil, to move more turns in a magnetic field of comparable size, thereby increasing the measurement performance. This variant is also more cost-effective than a wound coil and, due to an improved material combination between the conductor track and a substrate material, allows for better insulation. This makes applications of the field device at temperatures of the measuring medium exceeding 250°C possible within the scope of the present invention, for example, but not exclusively.

[0015] According to the invention, the printed circuit board is advantageously constructed in multiple layers, with a spirally arranged conductor track on every second layer, with 6 to 100 layers, preferably 10 to 50 layers. The multilayer arrangement allows for increased inductance and thus an improved measurement signal and also improved excitation or vibration excitation. The layers with the conductor tracks are also interconnected.

[0016] Coriolis flowmeters are familiar to flow measurement specialists. However, their combination with the aforementioned electrodynamic exciters and printed circuit board-based sensors is not widely known. This opens up new application areas for the corresponding classes of measuring instruments and offers particularly good measurement performance in existing fields.

[0017] Advantageous embodiments of the invention are the subject of the dependent claims.

[0018] Preferably and advantageously, the printed circuit board can be made of a ceramic material. This achieves particularly good temperature stability with correspondingly high electrical insulation of one conductor winding from the adjacent conductor windings. While it is already known to use ceramic-insulated wires in field devices of this type, the same insulation strength and thus reproducible manufacturability are not always guaranteed.

[0019] This ceramic material is also preferably a low-temperature single-fire ceramic or an LTCC ceramic. These ceramics are used in particular for the production of multilayer circuits based on sintered ceramic substrates. The conductive traces can be applied by screen printing or photochemical processes. The unfired ceramic sheets thus formed can then be individually structured, stacked, and optionally laminated. Sintering then takes place.

[0020] The printed circuit board can advantageously have at least one plate plane and a plate height perpendicular to the plate plane of a maximum of 500 µm, preferably 50 to 200 µm.

[0021] It is advantageous if the conductor tracks have a thickness of no more than 100 µm in the direction of the board height, preferably between 5 and 20 µm. This allows for a particularly high stacking density with correspondingly good electrical and thermal insulation.

[0022] The conductor tracks can advantageously be arranged in a spiral shape on the conductor track and have at least 4, preferably at least 6, turns. The spiral shape of the conductor track is preferably designed as an Archimedean spiral. A spiral shape according to the present invention can, in particular, approach a central point, but need not end or begin at this point; it can end before reaching this point.

[0023] Particularly advantageous is the arrangement of more than 40, preferably more than 60, turns with one or more conductor tracks on a single- and / or multi-layer printed circuit board.

[0024] An advantageous and preferred width of at least one - but in particular of all - conductor tracks is 30 to 350 µm, preferably 100 to 250 µm, wherein the width refers to a propagation direction that extends parallel to the plane of the plate.

[0025] An advantageous and preferred distance between two adjacent conductor windings of a layer is 30 to 200 µm, preferably between 60 to 140 µm.

[0026] In an advantageous embodiment, the printed circuit board can have a conductor track, in particular a top conductor track, which is completely covered with substrate material, wherein at least this conductor track, in particular at least one printed circuit board surface of this conductor track, has a protective layer to protect against mechanical and / or chemical damage.

[0027] Advantageously, at least one connecting wire, and in particular two connecting wires, can be fixed to the circuit board, wherein the connecting wire consists of a weldable metal with a melting point above 350°C. For example, copper or silver could be suitable materials.

[0028] It is also preferable and advantageous for the cross-sectional area of ​​the connecting wire to be larger, preferably at least twice as large, as the cross-sectional area of ​​the conductor track. Particularly preferably, the connecting wire has a substantially round cross-section with a radius of at least 50 µm.

[0029] It is advantageous if at least one turn, preferably all turns, of the conductor track has an area of ​​less than 3000 µm. 2 / turn, preferably smaller than 1500 µm 2 / have a coil.

[0030] The invention will now be explained in more detail with reference to several exemplary embodiments and the accompanying figures. These show: Fig. 1 a schematic partially cutaway view of a field device according to the invention with a partial section of a sensor / excitation unit; Fig. 2 Top view of a first variant of a printed circuit board in the sensor / excitation unit of the field device according to the invention; Fig. 3 Perspective view of a second variant of a printed circuit board for a sensor / excitation unit of a field device according to the invention; Fig. 4 Sectional view of the circuit board of the Fig. 3; Fig. 5 Side view of the circuit board of the Fig. 3 and Fig. 4; Fig. 6 Top view of the circuit board of the Fig. 3-5; and Fig. 7 Perspective view of the circuit board of the Fig. 3-6 with contacts.

[0031] The measuring principle of a Coriolis flowmeter is briefly discussed below using a two-pipe Coriolis flowmeter as an example. However, single-pipe or four-pipe Coriolis flowmeters are also known, which are likewise covered by the present invention.

[0032] The measuring principle is based on the controlled generation of Coriolis forces. These forces always occur in a system when translational (linear) and rotational (rotating) movements are superimposed. The magnitude of the Coriolis force depends on the moving mass, its velocity within the system, and thus on the mass flow. Instead of a constant rotational speed, the sensor exhibits an oscillation.

[0033] In this type of sensor, two parallel measuring tubes through which the fluid flows are set into opposite-phase vibration, forming a kind of tuning fork. The Coriolis forces generated at the measuring tubes cause a phase shift in the tube vibration. At zero flow, i.e., when the fluid is at rest, both tubes vibrate in phase. With mass flow, the tube vibration is decelerated at the inlet and accelerated at the outlet. The greater the mass flow, the greater the phase difference between the two vibrating measuring tubes. Electrodynamic sensors detect the tube vibration at both the inlet and outlet. System balance is achieved through the mutual vibrations of the two measuring tubes. The measuring principle is fundamentally independent of temperature, pressure, viscosity, conductivity, and flow profile.

[0034] In addition to mass flow, density measurement of the medium is also possible. The measuring tube is excited at its resonant frequency. As soon as the mass, and thus the density, of the oscillating system—that is, the measuring tube and the medium—changes, the excitation frequency is adjusted accordingly. The resonant frequency is therefore a function of the medium density. Based on this relationship, a density signal can be generated, for example, using a microprocessor.

[0035] Furthermore, a volumetric flow rate can be determined from the mass flow rate and the density.

[0036] To computationally compensate for temperature effects, the temperature at the measuring tube can be recorded. This signal corresponds to the process temperature and is also available as an output signal.

[0037] An example of a measuring device according to the invention is shown in Fig. 1 is represented as a Coriolis measuring device 1. The in Fig. The measuring device shown in Figure 1 is a two-pipe variant. A measuring medium is guided through two parallel pipes 2, which are arranged in a sensor housing 5. The sensor housing 5 has an elongated design and features flanges at each of its two end positions for connection to a process line. The measuring device also preferably includes a transmitter 4, in which an evaluation unit is arranged.

[0038] From the above description of the measuring principle, it follows that a pipe 2 through which a measuring medium flows must first be set into vibration by an exciter 3.II. Finally, the vibration frequency and / or the vibration amplitude of a pipe 2 is detected by sensors 3.I and 3.III.

[0039] In Fig. 1 The exciter 3.II and the sensors 3.I and 3.III are identical in construction as a sensor / exciter unit and are shown in a magnified section.

[0040] The tubes 2 each have a bend, with the exciter 3.II being arranged in the middle of the bend, relative to the longitudinal direction of the tubes. A first sensor 3.I for detecting the vibrations of the tube 2 in a flow direction R is arranged upstream of the exciter 3.II, and a second sensor 3.III for detecting the vibrations of the tube 2 in a flow direction R is arranged downstream of the exciter 3.II. The distance of both sensors 3.I and 3.III to the exciter 3.II is preferably the same. However, Coriolis measuring devices are also known which have tubes without a corresponding bend. The exciter 3.II and the sensors 3.I and 3.III are described in more detail below. The exciter and / or the sensors comprise a magnetic field-generating element 6 and a printed circuit board 7. The magnetic field-generating element 6 can, for example, and preferably, comprise one or more permanent magnets. Alternatively, however, a magnetic coil can also be provided.

[0041] These are arranged at a small distance from the circuit board, so that the magnetic field penetrates the circuit board at least in certain areas. At least one, but preferably several, conductive traces 9 made of an electrically conductive material, e.g., a metal such as copper or platinum, are incorporated on or into a substrate material 10 of the circuit board 7, the conductive trace being considered a component of the circuit board.

[0042] The substrate material 10 is formed in particular from an electrical insulator, e.g. from ceramic.

[0043] The magnetic field of the magnetic field-generating element can preferably be oriented such that the field lines of the magnetic field run perpendicular to the plate plane of the circuit board 7, at least in one region of the magnetic field.

[0044] The conductor track 9 is at least partially spirally wound onto or embedded in the printed circuit board 7. The conductor track also has two contacts 8 for tapping a measurement signal using a connecting wire (not shown here). Such an arrangement of a printed circuit board with a conductor track is commonly referred to as a printed circuit board coil or PCB coil.

[0045] Within the scope of the present invention, the circuit board 7 and the magnetic field-generating element 6 are defined as an arrangement 3 for generating pipe vibrations and / or for tapping off a pipe vibration-induced measurement signal.

[0046] If a pipe vibration-induced measurement signal is to be tapped, such a measurement signal can be induced by relative movement of the circuit board 7 to the magnetic field of the magnetic field-generating element 6, in particular a voltage.

[0047] If the arrangement 3 is to be used to excite a pipe oscillation, a force, in particular a Lorentz force, is generated by feeding an alternating current signal, for example at a resonance frequency of the oscillating pipes 2 or measuring tubes, through the conductor track 9 in combination with the magnetic field of the magnetic field-generating element 6.

[0048] In Fig. In 1 only one conductor track 9 is visible, however several conductor tracks can also be stacked on top of each other and spaced apart with a layer of substrate material.

[0049] In a preferred embodiment, the uppermost - i.e., actually exposed - conductor track 9 and / or the entire circuit board is provided with a protective layer, e.g. a glass layer, which serves as protection against mechanical damage to the uppermost conductor track.

[0050] The circuit board 7 or the magnetic field-generating element 6 is arranged on one of the first of the two tubes 2. The complementary component of the arrangement 3, i.e., the magnetic field-generating element 6 associated with the circuit board 7 or the circuit board 7 associated with the magnetic field-generating element 6, can be arranged on the second of the two tubes 2 or on a further element in or on the sensor housing 5.

[0051] In Fig. Figure 2 shows the arrangement of the conductor track 9 on the circuit board 7 in detail.

[0052] Fig. Figure 3-7 shows a second variant of a printed circuit board 17 for use in a measuring instrument according to the invention. This printed circuit board 17 has a central hole 23. The printed circuit board 17 is bounded by an inner edge with a diameter d1 and an outer edge with a diameter d2, the inner edge being coaxial with the outer edge.

[0053] The magnetic field of a corresponding magnetic field-generating element can preferably be oriented such that the field lines of the magnetic field are arranged perpendicular to the plane of the circuit board 7, at least in one region of the magnetic field.

[0054] Alternatively, and particularly preferred in this form of printed circuit board, a magnetic field-generating element, preferably a cylindrical magnetic field-generating element, can have a longitudinal axis and be guided through the central hole 23 of the printed circuit board 17.

[0055] Out of Fig. 4 and Fig. Figure 5 shows stacked layers with several layers 20a-20d of spirally wound and spaced-apart conductor tracks 19 and several layers 21a-21d of a substrate material, which are arranged between the layers 20a-20d of the conductor tracks 19. The stacked arrangement allows numerous windings to be placed on a printed circuit board.

[0056] The circuit board 17 also has connecting wires 22 for carrying away a measurement signal or for supplying an excitation signal, e.g., an excitation current. For this purpose, the following are provided in Fig. 3 and Fig. 4. Two contacts 18 are also provided on the circuit board for connecting the connecting wires.

[0057] The material of the connecting wires 22 should be compatible with the material of the conductor tracks so that they can be connected to the contacts 18. This can be done, for example, by a welding process. Reference sign 1 Coriolis measuring device 2 pipes 3.I Sensor 3.II Pathogen 3.III Sensor 4 transmitters 5 sensor housings 6 magnetic field generating element 7 printed circuit board 8 Contact 9 conductor track 10 Substrate material 17 printed circuit board 18 Contact 19 conductor tracks 20a-d several layers of spaced conductor tracks 21a-b several layers of a substrate material 22 connecting wires 23 central hole

Claims

Coriolis flowmeter (1) comprising a vibration-type sensor for measuring a flow rate and / or flow velocity of a fluid medium carried in a pipeline, wherein the sensor comprises a vibrating tube (2), and at least one electrodynamic exciter (3.II) for exciting the vibrating tube (2) into a oscillating motion and at least one electrodynamic sensor (3.I or 3.III), in particular two sensors (3.I and 3.III), for detecting a measurement signal generated by vibrations of the tube (2), wherein the exciter (3.II) and / or the sensor (3.I or 3.III)III) comprises at least two components, wherein a first component is designed as a printed circuit board (7, 17) with at least one conductor track (9, 19) for forming a printed circuit board coil, wherein a second component is designed as a magnetic field generating element (6), wherein one of the two components is arranged directly or indirectly on or in the vibrating tube (2) and excites the tube (2) to vibrate or receives the measurement signal by relative movement to the second of the two components, characterized in that at least one turn, preferably all turns, of the conductor track (9, 19) has an area of ​​less than 3000 µm² / turn, preferably less than 1500 µm² / turn. Coriolis flowmeter (1) according to claim 1, characterized in that the circuit board (7, 17) is designed as a low temperature fired ceramic (LTCC ceramic). Coriolis flowmeter (1) according to claim 1 or 2, characterized in that the circuit board (7, 17) has a plate plane and a plate height perpendicular to the plate plane of a maximum of 500 µm, preferably 50-200 µm. Coriolis flowmeter (1) according to claim 3, characterized in that the conductor track (9, 19) has a thickness in the direction of the plate height of a maximum of 100 µm, preferably of 5-20 µm. Coriolis flowmeter (1) according to one of the preceding claims, characterized in that the conductor track (9, 19) is arranged spirally on the circuit board (7, 17) and has at least 4, preferably at least 6 turns. Coriolis flowmeter (1) according to one of the preceding claims, characterized in that the circuit board (7, 17) is multilayered, wherein a spirally arranged conductor track (9, 19) is arranged on every second layer (20a-20d), with 6-100 layers (20a-d and 21a-d), preferably 10-50 layers (20a-d, 21a-d). Coriolis flowmeter (1) according to one of the preceding claims, characterized in that the printed circuit board (7, 17) has a conductor track (9, 19), in particular a top conductor track, which is completely covered with substrate material, wherein at least this conductor track (9, 19), in particular at least one printed circuit board surface of this conductor track (9, 19), has a protective layer to protect against mechanical and / or chemical damage. Coriolis flowmeter (1) according to one of the preceding claims, characterized in that at least one connecting wire (22), in particular two connecting wires, are fixed to the circuit board (7, 17), wherein the connecting wire (22) is made of a weldable metal with a melting point of over 350°C. Use of the Coriolis flowmeter (1) according to one of the preceding claims for measuring a medium with a medium temperature of more than 250°C.

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