Measuring device for measuring a quantity of a flowing fluid

Abstract

Measuring device for measuring at least one measurand, in particular a density, a flow rate and / or a viscosity, of a flowing fluid, with - a MEMS sensor (1, 7, 13) comprising at least one microfluidic channel (3, 9, 15) through which the fluid flows during measurement operation, comprising at least one channel section (5, 11, 17) that can be excited to vibrations of a predetermined useful vibration mode by means of an excitation device, and - a measuring device designed in such a way that it determines a property of the resulting vibrations of the at least one channel section (5, 11, 17) through which the fluid flows during the measuring operation and which is excited to vibrations, which depends on the respective measured quantity, wherein - the microfluidic channel (3, 9, 15) is a channel whose channel walls are made of titanium and which has an opening (19) on both the inlet and outlet sides, into which an end of a fluid line (21, 23) made of titanium, in particular a titanium tube, is inserted, in particular welded in, characterized in that - the fluid lines (21, 23) each comprise a freestanding section adjoining the end of the respective fluid line (21, 23) inserted into the opening (19), - the MEMS sensor (1, 7, 13) is supported by at least two, in particular two, three or four, freestanding support pillars (55, 57) made of titanium, and - the freestanding sections of the fluid lines (21, 23) each form one of these support pillars (55).

Description

[0001] The invention relates to a measuring device for measuring at least one measurand, in particular a density, a flow rate and / or a viscosity, of a flowing fluid, comprising a MEMS sensor, which includes at least one microfluidic channel through which the fluid flows during the measuring operation, which includes at least one channel section that can be excited to oscillations of a predetermined useful vibration mode by means of an excitation device, and a measuring device, which is designed in such a way that it determines a property of the resulting oscillations of at least one channel section through which the fluid flows and which is excited to oscillations during the measuring operation, which depends on the respective measurand.

[0002] Measuring devices of this type are used in metrology to measure the corresponding measured quantities.

[0003] MEMS sensors are micro-electromechanical systems used in metrology for the measurement of one or more quantities. MEMS sensors are typically manufactured using semiconductor manufacturing processes such as etching, oxidation, implantation, bonding, and / or coating, on single- or multi-layer wafers.

[0004] MEMS sensors of the type mentioned above can be used to implement different measurement principles.

[0005] An example of this is Coriolis mass flow measurement, which is based on the fact that Coriolis forces arise in a channel section through which fluid flows and which is excited to vibrate. These forces influence the resulting vibration pattern. The resulting vibration pattern of the channel section can be detected, for example, by a vibration sensor located at the inlet and an outlet of the channel section. In this case, the vibrations detected by the two vibration sensors have identical frequencies corresponding to the resulting vibration pattern. However, they are phase-shifted relative to each other by a phase shift that depends on the mass flow rate.

[0006] Another example is the Coriolis density measurement. This method also uses at least one channel through which the fluid flows during the measurement process, and which includes at least one channel section that can be excited to oscillation by means of an excitation device. With this measurement principle, the channel section is excited to oscillate at a resonance frequency. The resonance frequency depends on the density of the flowing fluid and can therefore be used to determine the density.

[0007] Another example is viscosity measurements. The viscosity of a fluid flowing through a channel section excited to vibrate a specific desired vibration mode can be determined, for example, based on the viscosity-dependent damping or the vibration quality of the resulting vibration. The energy required to excite the desired vibration mode can be used as a measure of the damping.

[0008] Corresponding MEMS sensors are generally manufactured from wafers made of silicon or a silicon-based material. For example, US Patent 6,477,901 B1 describes a measuring device for measuring at least one measurand, in particular density, flow rate, and / or viscosity, of a flowing fluid. - comprising a MEMS sensor made of silicon-based materials, comprising at least one microfluidic channel through which fluid flows during measurement operation, comprising at least one channel section that can be excited to vibrations of a predetermined useful vibration mode by means of an excitation device, and - comprising a measuring device designed in such a way as to determine a property of the resulting vibrations of at least one channel section through which the fluid flows and which is excited to vibrations during the measuring operation, which depends on the respective measured quantity.

[0009] A problem with silicon-based MEMS sensors is that microfluidic channels made of silicon or silicon-based materials are mechanically sensitive and exhibit only relatively low chemical resistance. Consequently, chemically aggressive and / or mechanically abrasive fluids flowing through the channel, such as potassium hydroxide or sodium hydroxide, can eventually reduce the channel wall thickness. This can alter the vibration characteristics of the channel sections and thus the sensor's measurement characteristics, ultimately even leading to sensor failure. Therefore, the range of fluids whose parameters can be measured with these sensors is limited.

[0010] Within certain limits, this problem can be remedied by using MEMS sensors of the type mentioned above, which have metallic channels. Examples are described in US 2010 / 0037706 A1. However, these MEMS sensors, just like the silicon-based MEMS sensors described in US 6477901 B1, each comprise a base mounted on a substrate that supports the channel(s). The fluid must therefore be fed into the respective channel on the inlet side through the substrate and the base, and discharged on the outlet side through the base and the substrate. Additionally, the MEMS sensor must be mounted at the point of use and connected to a process line provided at the point of use, through which the fluid flows during measurement. For this purpose, the MEMS sensor can, for example, be mounted on a line segment as described in DE 102014108351 A1, which can then be inserted into the process line.The conductor segment described in DE 10 2014 108 351 A1 comprises, for each channel of the MEMS sensor, a supply line via which an inlet-side interior of the conductor segment is connected to an inlet provided for the respective channel in the substrate and a discharge line via which an outlet-side interior of the conductor segment is connected to an outlet provided for the respective channel in the substrate.

[0011] The production of MEMS sensors with a base mounted on a substrate to support the channel(s), their assembly at the point of use, and the connection of the sensor's channel(s) to the process line consequently requires a comparatively large number of process steps and is therefore correspondingly complex.

[0012] Furthermore, in measuring devices constructed as described above, a comparatively large number of different materials regularly come into contact with each other in various ways during measurement operation. These contacts include direct contacts, which occur via mechanical connections, especially joining, between components made of different materials, as well as indirect contacts, which arise via the fluid flowing through components made of different materials.

[0013] Direct contact carries the risk of thermomechanical stresses developing due to the differing coefficients of thermal expansion of the materials. These stresses are particularly detrimental when transferred to channel sections susceptible to vibration, where they can affect the vibration behavior and thus impair the achievable measurement accuracy. Indirect contact via the fluid can also have adverse effects. For example, electrochemical reactions can be triggered by ion-containing fluids such as salt water, which can lead to material changes over time and impair the sensor's measurement characteristics.

[0014] Publications US 2008 / 0 314 161 A1 and US 2015 / 0 114 137 A1 each disclose MEMS sensors with different materials for the channels, including metallic materials such as titanium. Publication DE 10 2013 017 317 A1 discloses a MEMS sensor that uses a bonding layer, which in particular comprises a polymer. Publication US 2009 / 0 283 844 A1 discloses a sandwich structure for a MEMS sensor with a semiconductor wafer, a glass wafer, and a metallic wafer, wherein the fluid channels are prepared in the semiconductor wafer.

[0015] It is an object of the invention to provide a measuring device with a MEMS sensor for measuring at least one measurand of a flowing fluid of the type mentioned above, which overcomes the disadvantages of the aforementioned prior art.

[0016] The invention comprises a measuring device for measuring at least one measured quantity, in particular a density, a flow rate and / or a viscosity, of a flowing fluid, with - a MEMS sensor comprising at least one microfluidic channel through which fluid flows during measurement operation, comprising at least one channel section that can be excited to vibrations of a predetermined useful vibration mode by means of an excitation device, and - a measuring device designed in such a way as to determine a property of the resulting vibrations of at least one channel section through which the fluid flows and which is excited to vibrations during the measuring operation, which is dependent on the respective measured quantity, and which is characterized in that the microfluidic channel is a channel whose channel walls are made of titanium and which has an opening on both the inlet and outlet sides, into which an end of a fluid line made of titanium, in particular a titanium tube, is inserted, in particular welded in, - the fluid lines each comprise a freestanding section adjoining the end of the respective fluid line inserted into the opening, - the MEMS sensor is supported by at least two, in particular two, three or four, freestanding titanium support pillars, and - the freestanding sections of the fluid lines each form one of these support pillars.

[0017] A further development of the invention is characterized in that, in addition to the support pillars formed by the freestanding sections of the fluid lines, at least one further support pillar supporting the MEMS sensor, in particular a titanium tube or a titanium column, in particular a support pillar inserted, in particular welded, into a blind hole bore provided in the MEMS sensor, in particular in a frame supporting the channel sections that can be excited to vibrations, is provided.

[0018] A second advanced training course is characterized by the fact that the MEMS sensor - a lower part produced from a first titanium wafer, in which a recess open towards a top side of the first wafer is provided for each microfluidic channel, the shape of which is the same as the shape of an interior space of the respective channel through which flow occurs during measurement operation, - comprises a top part produced from a second titanium wafer and connected to the bottom part, which seals off the interior spaces of the channels formed by the recesses in the bottom part to the outside, - comprises recesses extending through the bottom part and the top part for each channel section that can be excited to vibration, arranged on both sides of the respective channel section and exposing the respective channel section on both sides, and - is mounted on the fluid lines inserted into the openings.

[0019] A third type of further training is characterized by the fact that - the MEMS sensor includes an outer frame that supports the exposed channel sections, - each channel comprises an inlet-side and an outlet-side channel end located within the frame, and - the openings in the frame are recesses in the frame, each adjacent to an interior space of one of the channel ends.

[0020] A further development of the third further development is characterized by the fact that the frame, at least in its areas encompassing the openings, has a frame width that is greater than or equal to the width of the channel section(s) that can be excited to vibration, and / or has a frame height that is greater than or equal to the height of the channel section(s) that can be excited to vibration.

[0021] Preferred embodiments are characterized by the fact that the fluid lines have a diameter of 600 µm or greater, in particular 700 µm to 800 µm, and / or a line wall thickness of 20 µm or greater, in particular 25 to 100 µm, and / or - the channel sections have a width of at least one, in particular several hundred µm, a height of at least one, in particular several hundred µm, and / or a wall thickness in the range of 40 µm to 60 µm.

[0022] A fourth type of advanced training is characterized by the fact that - the measuring device comprises a support structure for the MEMS sensor, in particular the MEMS sensor and at least one further component, in particular electronics, a component of the excitation device and / or a component of the measuring device, in particular a device for generating a magnetic field or a counter electrode module, and / or the measuring device, in particular a support structure on which the MEMS sensor is mounted on support pillars comprising freestanding sections of the fluid lines, - the support includes a support area in which a bore leading through the support area is provided for each fluid line, and - the fluid lines each end in the corresponding bore or run through the corresponding bore.

[0023] A fourth-level advanced training course is characterized by the fact that - the support comprises a plate, - the fluid lines run through the bores to a side of the plate facing away from the MEMS sensor, where they can be connected to a process line, in particular via process connections, especially connectors, provided at their ends.

[0024] An alternative form of further education, the fourth type of further education, is characterized by the fact that - the support is designed as part of a line segment, in particular a line segment equipped with a process connection, in particular a flange, on both the inlet and outlet sides, in particular a line segment that can be inserted into a process line, - each fluid line serving as a supply line to the MEMS sensor runs through the associated bore in the carrier to an inlet-side entry area of ​​the line segment, and - each fluid line serving as a discharge line runs through the associated bore in the support to an outlet-side discharge area, in particular an discharge area separated from the inlet area by a partition wall provided in the line segment or an outlet area connected to the inlet area via a passage.

[0025] A further development of the fourth development is characterized by the fact that a housing surrounding the MEMS sensor, in particular the MEMS sensor and at least one other component mounted on the carrier, in particular a component of the excitation device and / or a component of the measuring device, in particular an evacuated housing, is mounted on the carrier.

[0026] Further variations are characterized by the fact that - the MEMS sensor comprises two parallel straight channels, each containing a channel section that can be excited to lateral vibrations, - the MEMS sensor comprises a channel with an essentially U-shaped profile, the two parallel legs of which each comprise a channel section that can be excited to lateral vibrations, or - the MEMS sensor comprises a channel with an essentially u- or Ω-shaped profile, which includes a u- or Ω-shaped channel section that can be excited to torsional vibrations.

[0027] The measuring devices according to the invention have the advantage that the fluid, on its way to the MEMS sensor, through the sensor, and out of the sensor, comes into contact exclusively with the titanium fluid lines and the titanium channel(s). Titanium is highly resistant both mechanically and chemically, so that the measuring devices according to the invention can be used to measure parameters of a large variety of different fluids without the risk of mechanical abrasion and / or chemical reactions, such as those that can occur in measuring devices with components made of different materials that are in direct or indirect contact with each other via the fluid, leading to a permanent change in the vibration characteristics of the channel section(s) that could be excited to vibration, thus impairing the measurement.The measuring devices according to the invention thus enable long-term stable measurements of measured quantities of a wide range of different fluids.

[0028] Since the fluid lines and the associated channels are made of the same material, thermomechanical stresses that could affect the vibration behavior of the channel sections are avoided. This also prevents thermomechanical stresses that could affect the joints between the fluid lines and the openings of the channel(s). The optional mounting of the MEMS sensor on support pillars provides further decoupling, enhancing these advantages.

[0029] Furthermore, the use of titanium as the base material for the MEMS sensor and the fluid lines offers the advantage from a manufacturing perspective that titanium can be processed using both methods established in microsystems technology, such as etching, and methods known from conventional metalworking, such as milling, turning, and waterjet cutting. In addition, joints between titanium components can be created using both joining methods established in microsystems technology, such as thermal compression bonding, and joining methods known from conventional metalworking, such as laser beam welding. Thus, macromechanical components can not only be connected to micromechanical components, but macromechanical components incorporating micromechanical elements can also be created.

[0030] The invention and further advantages will now be explained in more detail with reference to the figures, which illustrate three exemplary embodiments. Identical parts in the figures are designated with the same reference numerals. To be able to depict components of very different sizes, the figures are not drawn to scale. Fig. Figure 1 shows: a measuring device with a MEMS sensor mounted on a plate; Fig. Figure 2 shows: a measuring device with a MEMS sensor mounted on a cable segment; Fig. Figure 3 shows a top view of the MEMS sensor from Fig. 1 and Fig. 2; Fig. Figure 4 shows: a sectional drawing of the MEMS sensor from Fig. 1 and Fig. 2 in a section plane passing through the channels; Fig. Figure 5 shows a sectional drawing of the MEMS sensor from Fig. 1 and Fig. 2 in the in Fig. 3 displayed section plane A-Ac; Fig. Figure 6 shows: a MEMS sensor with a u-shaped channel with two channel sections that can be excited to lateral vibrations; Fig. Figure 7 shows: a MEMS sensor with a U-shaped channel with a U-shaped channel section that can be excited to torsional vibrations; and Fig. Figure 8 shows a measuring device with a MEMS sensor mounted on two support pillars formed by sections of the fluid lines and two further support pillars.

[0031] The invention relates to measuring devices for measuring at least one measurand, e.g., density, flow rate, and / or viscosity, of a flowing fluid, comprising a MEMS sensor, an excitation device, and a measuring device. The MEMS sensor of these measuring devices comprises at least one microfluidic channel through which the fluid flows during measurement operation, and which includes at least one channel section that can be excited to oscillations of a predetermined useful vibration mode by means of the excitation device.

[0032] Additionally, the measuring device is designed to determine a property of the resulting vibrations of at least one channel section through which the fluid flows and which is excited to vibrate during the measurement process, a property that depends on the respective measured quantity. For vibration excitation and for the metrological measurement of the properties of the resulting vibrations that depend on the respective measured quantity of the fluid, electrostatic, piezoelectric, or electromagnetic excitation devices, as well as electrostatic, piezoelectric, or electromagnetic measuring devices known from the prior art, can be used. Various measurement methods known from the prior art, such as the aforementioned Coriolis mass flow measurement, the Coriolis density measurement, and / or viscosity measurements, can be performed with the measuring device.These methods are known from the prior art and are therefore not described in detail here.

[0033] Fig. 1 and Fig. Figures 2 each show an embodiment of a measuring device according to the invention. Fig. Figure 3 shows a top view of the [unclear] in the Fig. 1 and Fig. 2 as an exemplary embodiment of the MEMS sensor 1. The MEMS sensor 1 comprises two parallel, straight channels 3, each of which is used to detect vibrations of a predetermined, in Fig. 3 each of which is indicated by a double arrow and comprises a channel section 5 that can be excited by the useful vibration mode. Fig. Figure 4 shows MEMS sensor 1 of Fig. 3 in a section plane passing through the channels 3. Fig. Figure 5 shows MEMS sensor 1 of Fig. 3 in the Fig. 3 Section plane A-Ac shown. In this MEMS sensor 1, the two parallel channel sections 5 are preferably excited to lateral vibrations, experiencing deflections in a plane of vibration perpendicular to its longitudinal axis – preferably excited out of phase. Alternatively, a MEMS sensor with a different number and / or shape of channels and / or channel sections capable of being excited to vibrations can also be used. An example is a MEMS sensor that only uses one of the two channels shown in the Fig. The straight channels shown in figures 3 to 5 comprise the channel section that can be excited to vibration. Another example is a MEMS sensor 7 with only one channel 9 with an essentially U-shaped profile. Fig. Figure 6 shows a section in a plane passing through the channel 9. In this channel 9, the two parallel legs of the U-shaped channel 9 each form a channel section 11 that can be excited to oscillate. Here, too, the two channel sections 11 are preferably excited to lateral oscillations in opposite phases, during which they are deflected perpendicular to their longitudinal axis.

[0034] Fig. Figure 7 shows a further embodiment of a MEMS sensor 13 with a substantially U-shaped channel 15 comprising a U-shaped channel section 17 that can be excited to oscillation. The latter can, for example, be excited to torsional oscillations about an axis TA extending through the two ends of the U-shaped channel section 17. In this process, the channel section 17 is deflected perpendicular to the plane defined by the U-shape, with the region of the channel section 17 opposite the ends experiencing the greatest deflection amplitude. Alternatively, the U-shaped channel section 17 shown here can be configured as a substantially Ω-shaped channel section.

[0035] The measuring devices according to the invention are characterized in that each microfluidic channel 3, 9, 15 provided in the MEMS sensor 1, 7 or 13 is a channel whose channel walls are made of titanium and which has an opening 19 on both the inlet and outlet sides, into which one end of a fluid line 21, 23 made of titanium is inserted. Fig. 1 and Fig. Figure 2 shows a longitudinal section of the measuring device in a section plane that corresponds to the one shown in the Fig. The section plane B-Bc shown in Figure 3 passes through the MEMS sensor 1. The openings 19 are preferably recesses provided in a channel wall area adjacent to the respective inlet or outlet end of the respective channel 3. Titanium tubes are particularly suitable as fluid lines 21, 23.

[0036] By inserting the titanium fluid lines 21, 23 directly into the openings 19 in the titanium channel wall sections, the fluid is ensured to come into contact exclusively with the titanium fluid lines 21, 23 and the titanium channels 3, 9, 15 on its way to, through, and out of the MEMS sensor 1, 7, 13. Titanium is highly resistant both mechanically and chemically, so that the measuring devices according to the invention can be used to measure parameters of a wide variety of different fluids. Furthermore, this avoids chemical reactions that can occur in measuring devices with components made of different materials that are in direct or indirect contact with each other via the fluid.In the measuring devices according to the invention, MEMS sensors 1, 7, 13 are preferably used, comprising a lower part 25 produced from a first titanium wafer and an upper part 27 connected thereto, produced from a second titanium wafer. In the lower part 25, a recess 29, 31 open towards a top surface of the first wafer is provided for each microfluidic channel 3, 9, 15, the shape of which corresponds to the shape of an interior space of the respective channel 3, 9 or 15 through which the fluid flows during measurement operation. The upper part 27 is designed such that it seals the recesses 29, 31 in the lower part 25, which form the interior spaces of the channels 3, 9, 15 through which the fluid flows during measurement operation.

[0037] By mounting these MEMS sensors 1, 7, 13, which essentially consist of only two components, namely the lower part 25 and the upper part 27, directly onto the fluid lines 21, 23 inserted into the openings 19, a reduction in the number of components is achieved. This reduces the manufacturing costs and the overall flow resistance that the fluid has to overcome when flowing through the measuring device.

[0038] In the production of measuring devices according to the invention, the procedure is preferably such that, in a first process step, the recesses 29 or the recess 31 are produced in the first titanium wafer. For this purpose, anisotropic etching processes known from the prior art are preferably used, with which recesses with a comparatively high aspect ratio can also be produced. Examples of this are the process known under the abbreviation MARIO (Metal Anisotropic Reactive Ion Etching with Oxidation), as well as the TIDE process described by ER Parker, BJ Thibeault, M.F. Aimi, MP Rao and NC MacDonald, published in the Journal of the Electrochemical Society, 152 (52) C675-C685, in 2005 under the title 'Inductively Coupled Plasma Etching of Bulk Titanium for MEMS Applications'.The second titanium wafer is then positioned on the first wafer in such a way that it closes the recess(s) 29, 31 and bonds to the first wafer. Suitable bonding processes for joining the two wafers include, for example, thermocompression bonding. In thermocompression bonding, the joining surfaces of the lower part 25 and the upper part 27 are preferably coated with an auxiliary layer, e.g., a gold layer, for example, by sputtering or vapor deposition. The lower part 25 and the upper part 27 are then positioned on top of each other and heated under pressure to a joining temperature. Subsequently, in the assembly thus produced, recesses 33, 35, 37 are provided on both sides of each channel section 5, 11, 17 that can be excited to vibration. These recesses expose the respective channel section 5, 11, 17 on both sides and extend through the lower part 25 and the upper part 27. During the manufacture of the... Fig. 3 and Fig. For the MEMS sensors 1 and 7 shown in section 6, three parallel recesses 33 with a rectangular base are created. During the manufacturing process of the Fig. In the MEMS sensor 13 shown in Figure 7, a recess 35 with a rectangular base and a recess 37 with a U-shaped base (as seen from above) are created. The recess 35 with the rectangular base is located in the finished sensor between the legs of the vibrating channel section 17. The recess 37 with the U-shaped base surrounds the vibrating U-shaped channel section 17 on its outer side.

[0039] The assembly of upper and lower parts 25, 27 is preferably designed such that it includes an outer frame 39, which in the embodiments shown here is rectangular and which supports the channel sections 5, 11 and 17 exposed via the recesses 33, 35 and 37 respectively. The frame 39 facilitates the handling, in particular the assembly, of the MEMS sensor 1, 7, 13 and protects the exposed channel sections 5, 11, 17 enclosed therein.

[0040] The channel sections 5, 11, 17 can be designed, for example, as channel sections 5, 11, 17 with a square or rectangular cross-section, having a width B of at least one, preferably several 100 µm, a height H of at least one, preferably several 100 µm, and a wall thickness in the range of 40 µm to 60 µm.

[0041] In a further step, the openings 19 for receiving the fluid lines 21, 23 are created in the first wafer. The openings 19 created from the underside of the first wafer below the channel ends in the lower part 25 are in the Fig. 4, Fig. 6 and Fig. Elements 7 located below the depicted section plane are shown as dashed lines. Depending on the size of the openings 19, suitable methods include those known from microsystems technology, such as the etching processes used to create the recesses 33, 35, 37, as well as methods known from classical metalworking, such as drilling or milling.

[0042] Depending on the size and desired manufacturing tolerance of the recesses 33, 35, 37 and / or the openings 19, the recesses 33, 35, 37 and / or the openings 19 can also be produced by a rough pre-machining using a method known from classical metalworking, which is then followed by post-machining using a significantly more precise method known from microsystems technology.

[0043] In addition, during the manufacture of the MEMS sensor 1, 7, 13, depending on the type of excitation direction and the measuring device, any necessary manufacturing steps are carried out to produce components of the excitation direction and / or the measuring device that are to be provided on the MEMS sensor 1, 7, 13 and / or connected to the MEMS sensor 1, 7, 13. As a possible example, the following are described in the Fig. The embodiments shown in Figures 1 to 3 depict an electromagnetic excitation device and an electromagnetic measuring device, which can also be used analogously in conjunction with the device shown in Figure 1 to 3. Fig. The MEMS sensor 7 shown in Figure 6 can be used. This includes a drive cable 43, which is attached to an electronics unit 41 and connected to a top surface of the MEMS sensor 1 opposite the openings 19. The drive cable 43 runs from a connection located on a first edge 45 of the frame 39 along one of the two channels 3 to the opposite second edge 47 of the frame 39 and from there back along the other channel 3 to a second connection located on the first edge 45 of the frame 39. The excitation device also includes a device 49 that generates a magnetic field perpendicular to the longitudinal axes of the two channel sections 5. For this purpose, a device comprising two magnetic poles N, S, one of which is located above and the other below the channel sections 5, 11, can be used. During measurement operation, an excitation signal, e.g., an alternating current signal, is supplied to the drive cable 43 via the electronics unit 41.Lorentz forces act on the areas of the drive line 43 permeated by the magnetic field, causing the excitation of the useful vibration modes of the channel sections 5 connected to the drive line 43. Similarly, the electromagnetic measuring device, shown here only as a possible example, comprises a measuring line 51 for each channel 3. This line runs from a connection located on the first edge 45 of the frame 39 along the respective channel 3 to the opposite second edge 47 of the frame 39, and from there back along the frame 39 to a second connection located on the first edge 45. The measuring lines 51 are connected to the electronics 41.The latter detects, during measurement operation, a signal induced by the magnetic field through the movement of the sections of the respective measuring line 51 running on the oscillating channel sections 5. Based on this signal, the property of the resulting oscillations, which depends on the measured quantity, is then determined. In this embodiment, an insulating layer 53, e.g., an oxide layer or a nitride layer, is applied to the top surface of the assembly consisting of the lower part 25 and the upper part 27 in a first process step. The drive line 43 and the measuring lines 51 are then applied to this layer, e.g., by sputtering or vapor deposition.

[0044] Following the completion of the MEMS sensor 1, 7, 13, the fluid lines 21, 23 are inserted into the openings 19. For this purpose, the ends of the fluid lines 21, 23 are preferably inserted precisely into the respective opening 19 up to a stop that limits the opening 19 and secured there. Methods known from conventional metalworking, such as laser welding, are particularly suitable for securing the lines.

[0045] In conjunction with MEMS sensors 1, 7, 13 and a frame 39 supporting the channel sections 5, 11, 17 that can be excited to vibration, the channels 3, 9, 15 are preferably designed such that their inlet and outlet ends are each located within the frame 39. In this case, the openings 19 are recesses in the frame 39 adjacent to the interior of the respective channel end. Since the frame 39 is not excited to vibration, the frame 39 can readily have, at least in the areas encompassing the openings 19, a frame width that is greater than or equal to the width of the channel sections 5, 11, 17 that can be excited to vibration, and / or a frame height that is greater than or equal to the height of the channel sections 5, 11, 17 that can be excited to vibration.This can be achieved in manufacturing, for example, by thinning the first wafer from the underside opposite the top part 27 in the finished sensor in the area surrounded by the frame 39. Depending on the size of the area to be thinned, methods known from microsystems technology, such as the etching process mentioned above, methods known from classical metalworking, such as drilling or milling, or a combination of these methods can be used.

[0046] The dimensions of the openings 19 can be freely selected within relatively wide limits by adjusting the frame height and / or frame width accordingly. The dimensions of the openings 19, and thus also of the fluid lines 21, 23, are not limited by the dimensions of the respective channel 3, 9, 15, the interior of the respective channel 3, 9, 15, or by the wall thickness of the channel sections 5, 11, 17 that can be excited to vibration. In measuring devices according to the invention, fluid lines 21, 23 are preferably used that are mechanically stable enough to support the MEMS sensor 1, 7, 13. These fluid lines 21, 23 preferably have a diameter of 600 µm or greater, preferably in the range of 700 µm to 800 µm. They preferably have a conductor wall thickness of greater than or equal to 20 µm, which is preferably in a range of 25 µm to 100 µm.This offers the advantage that the fluid lines 21, 23 can not only be used as supply and return lines through which the fluid flows during measurement operation, but can also each comprise a support pillar 55 carrying the MEMS sensor 1. For this purpose, the fluid lines 21, 23 each have a freestanding section, forming the support pillar 55, adjoining the end of the respective fluid line inserted into the opening 19. This embodiment is shown in the [reference to be added]. Fig. 1 and Fig. Figure 2 shows the MEMS sensor 1 being supported by four support pillars 55 formed by the freestanding sections of the four fluid lines 21, 23. In principle, two support pillars 55 arranged at a sufficient distance from each other are enough to ensure stable mounting of the MEMS sensor. Thus, the Fig. 6 The MEMS sensor 7 shown can be mounted, for example, on two support pillars formed by freestanding sections of the fluid lines inserted in its two openings 19.

[0047] In addition to the support pillars 55 formed by sections of the fluid lines 21, 23, at least one further support pillar 57 can be provided. The further support pillars 57 are preferably made of titanium and can be designed, for example, as hollow titanium tubes or as solid titanium columns. Further support pillars 57 are particularly useful when a MEMS sensor with only one channel comprising two closely spaced end regions is used. Furthermore, they are particularly useful in conjunction with MEMS sensors in which mechanical forces are generated by vibrations excited during measurement operation, which in total lead to a non-negligible mechanical stress on the components of the measuring device supporting the channel section or sections. The latter can occur, for example, in the case described in Fig. This is the case with the MEMS sensor 13 shown in Figure 7. There, the U-shaped channel section 17, excited to torsional vibrations, exerts resulting forces on its anchoring in the frame 39, which, depending on the mass and dimensions of the channel section 17, can reach a non-negligible magnitude. While the forces caused by the vibrations of the channel sections 5, 11 in the Fig. The forces exerted on the anchoring of the MEMS sensors 1, 7, represented by figures 3 to 6, during antiphase excitation, essentially cancel each other out, and the torsional vibrations of the U-shaped channel section 17 of the in Fig. The MEMS sensor 13 shown in 7 is not compensated by opposing forces.

[0048] If a further support pillar 57 is provided, it is preferably placed in a Fig. 7. As an option, a blind hole 59, shown as a dashed line, is inserted in the frame 39, positioned such that the support pillars 55 formed by the sections of the fluid lines 21, 23 and the further support pillar 57 are arranged in a triangle. If two further support pillars 57 are provided, these are preferably, as an option, in Fig. 7 blind bores 61 shown in dashed lines are inserted in the frame 39, which are positioned such that the support pillars 55 formed by the sections of the fluid lines 21, 23 and the two further support pillars 57 are arranged in a rectangle or square. Fig. Figure 8 shows a corresponding measuring device in a structure running through one of the support pillars 55 and one of the other support pillars and in the Fig. The section plane CC' shown in Figure 7 runs through the section plane 13 passing through the MEMS sensor. It differs from the one shown in Figure 7. Fig. 2 measuring device shown, by the fact that it Fig. The MEMS sensor 13 shown in Figure 7 is supported by two support pillars 55 formed by the sections of the two fluid lines 23 and by two further support pillars 57. Measuring devices according to the invention are preferably equipped with a carrier 63, 65, via which the measuring device can be mounted at the installation site and its fluid lines 21, 23 can be connected to a fluid-carrying process line provided at the installation site, e.g., a simple line or a section of a piping system. The carrier 63, 65 comprises a preferably planar support area in which a bore extending through the support area is provided for each fluid line 21, 23, into which the respective fluid line 21, 23 is inserted and fixed there in a position corresponding to the height of the support pillars 55.

[0049] The fluid lines 21 and 23 can be inserted such that they each terminate in their respective bore. In this case, the support structure is preferably made of titanium. Fastening can be achieved, for example, by laser welding.

[0050] Preferably, the fluid lines 21, 23 pass through the bores. This offers the advantage that the fluid flowing through the fluid lines 21, 23 does not come into contact with the support area. In this case, the support area can be made of metal, e.g., titanium or stainless steel, or of a plastic, e.g., polystyrene, polyamide, or polycarbonate. Depending on the material of the support area, it is attached, e.g., by laser welding, soldering, or bonding.

[0051] At the in Fig. In the embodiment shown in Figure 1, the carrier 63 comprises a plate. Here, the fluid lines 21 run through bores provided in the plate to a side of the plate facing away from the MEMS sensor 1, where they can be connected, for example, via process connections 67 provided at their ends, such as connectors shown here only schematically, to a process line provided at the installation site.

[0052] At the in Fig. In the embodiment shown in Figure 2, the support 65 is designed as part of a pipe segment that can be inserted into the process line and is equipped with a process connection 69, e.g., a flange, at both the inlet and outlet ends. In this variant, the support area encompassing the bores is formed by a wall section of the pipe segment.

[0053] In this variant as well, the fluid lines can terminate in the bores or in an immediately adjacent interior space of the line segment. Preferably, however, the fluid lines 23 serving as supply lines extend through the bores to an inlet-side inlet region 71 of the line segment. Similarly, the fluid lines 23 serving as discharge lines preferably extend through the bores to an outlet-side outlet region 73 of the line segment. The inlet region 71 and the outlet region 73 can be separated from each other by a partition 75 provided in the line segment or by a Fig. The two passages shown as an option, 77, are connected to each other.

[0054] In this variant, the ends of the fluid lines 23 opposite the openings 19 are preferably each fixed in a holder 79 provided in the inlet and outlet areas 71 and 73, respectively. The aforementioned dimensions of the fluid lines 23 offer the advantage that the fluid lines are, on the one hand, stable enough to form the support pillars 55 and, on the other hand, flexible enough to be incorporated into the openings 71 and 73. Fig. The fluid lines 23 are to be brought into the curved shape shown in Figure 2. For this purpose, the fluid lines 23 are preferably inserted into the openings 19 as straight lines, the ends of which opposite the respective opening 19 are chamfered according to the direction of curvature intended for the respective fluid line 23. The fluid lines 23 are inserted through the bores into the line segment, whereby their free ends, upon reaching the wall of the line segment opposite the bores, are deflected towards the inlet or outlet area 71, 73, respectively, due to the orientation of their chamfer, according to their function as supply or outlet lines. Subsequently, the fluid lines 23 are secured in the bores at a position corresponding to the height of the support pillars 55. Finally, the free ends of the fluid lines 23 are preferably inserted into the respective holder 81 and fixed there.

[0055] In measuring devices, such as the one in Fig. In the measuring device shown in Figure 8, which, in addition to the support pillars 55 formed by sections of the fluid lines 21, 23, has at least one further support pillar 57, a blind hole is preferably provided in the support 65, 67 for each further support pillar 57. The end of the respective further support pillar 57 opposite the end inserted into the blind hole 59 or 61 in the MEMS sensor 13 is inserted into this bore. Preferably, the support area of ​​the support 65, 67 not only carries the MEMS sensor 1, 7, 13 but preferably also other components of the measuring device required for carrying out the measurements, such as the electronics 41 connected to the terminals of the MEMS sensor 1, 7, components of the excitation device, and / or components of the measuring device. As an example, the component shown in the figures is mounted on the supports 65, 67. Fig. 1 and Fig. The measuring devices shown in Figure 2 each have the electronics 41, connected here via wire bonds to the terminals of the MEMS sensor 1, 7, 13, and the device 49 for generating the magnetic field mounted. The poles N, S arranged above and below the channel sections 5, 11 can, for example, be extensions or end pieces of a substantially horseshoe-shaped, in Fig. 1 in a circled additional figure, the magnetic field generating device is designed to be slid over the MEMS sensor 1, 7 from the side and attached to the carrier 65, 67, e.g. glued on.

[0056] Alternatively, other excitation devices and measuring devices can be used. For example, in conjunction with the in Fig. 7 and Fig. Figure 8 shows a MEMS sensor 13 comprising an excitation device including at least one excitation capacitor and a measuring device including at least one measuring capacitor. The excitation capacitors and the measuring capacitors each have an electrode arranged on a surface of the channel section 17 and a stationary counter electrode, preferably mounted on the support 65 of the measuring device. For example, torsional vibrations can be excited by means of an excitation capacitor arranged in the area connecting the legs of the channel section 17, and the resulting vibration can be detected by means of at least one measuring capacitor arranged in the area of ​​one of the two legs. The counter electrodes are preferably mounted on a Fig.The module 81, shown only schematically, is mounted on the carrier 65 and connected to electronics 83, which are also preferably arranged on the carrier 65 of the measuring device. The electrodes are preferably arranged on an insulating layer on the corresponding surfaces of the channel section 17 opposite the module 81 and are connected to the electronics 83 via conductors applied to an insulating layer on the MEMS sensor 13.

[0057] Optionally, a housing 85 can be mounted on the carrier 65, 67, which surrounds the MEMS sensor 1, 7, 13, and preferably also other components of the measuring device mounted on the carrier 65, 67. Optionally, the housing 85 can be designed as an evacuated housing 85, e.g., to reduce the damping of the vibrations of the channel sections 5, 11, 17.

[0058] In comparison to the previously mentioned measuring devices known from the prior art, in which the MEMS sensor comprises a base mounted on a substrate and supporting the channel(s), which is then mounted on a support via a generally planar connection, the measuring devices according to the invention have a smaller number of components. This reduces the manufacturing effort associated with the production and connection of the components. Furthermore, the freestanding sections of the support pillars 55, as well as any additional support pillars 57, reduce the mechanical and thermomechanical stresses that can be transmitted to the MEMS sensor 1, 7, 13, in particular to its vibration-prone channel sections 5, 11, 17, due to the necessary mounting of the sensor. 1 MEMS sensor 3-channel 5 Canal section 7 MEMS sensor 9-channel 11 Canal section 13 MEMS sensor 15 Channel 17 Canal section 19 Opening 21 Fluid line 23 Fluid line 25 Lower part 27 Top 29 Exclusion 31 Exclusion 33 recess 35 recess 37 recess 39 frames 41 Electronics 43 Drive line 45 first edge of the frame 47 second edge of the frame 49 Device for generating a magnetic field 51 Measuring lead 53 Insulation layer 55 support pillars 57 supporting pillars 59 Blind hole drilling 61 Blind hole drilling 63 carriers 65 carriers 67 Process connection 69 Process connection 71 Entrance area 73 Exit area 75 Partition wall 77 Passage 79 bracket Module 81 83 Electronics 85 cases

Claims

[1] Measuring device for measuring at least one measured quantity, in particular a density, a flow rate and / or a viscosity, of a flowing fluid, with - a MEMS sensor (1, 7, 13) comprising at least one microfluidic channel (3, 9, 15) through which the fluid flows during measurement operation, comprising at least one channel section (5, 11, 17) that can be excited to vibrations of a predetermined useful vibration mode by means of an excitation device, and - a measuring device designed in such a way that it determines a property of the resulting vibrations of the at least one channel section (5, 11, 17) through which the fluid flows during the measuring operation and which is excited to vibrations, which depends on the respective measured quantity, wherein - the microfluidic channel (3, 9, 15) is a channel whose channel walls are made of titanium and which has an opening (19) on both the inlet and outlet sides, into which an end of a fluid line (21, 23) made of titanium, in particular a titanium tube, is inserted, in particular welded, characterized by , that - the fluid lines (21, 23) each comprise a freestanding section adjoining the end of the respective fluid line (21, 23) inserted into the opening (19), - the MEMS sensor (1, 7, 13) is supported by at least two, in particular two, three or four, freestanding support pillars (55, 57) made of titanium, and - the freestanding sections of the fluid lines (21, 23) each form one of these support pillars (55). [2] Measuring device according to claim 1, characterized by, that in addition to the support pillars (55) formed by the freestanding sections of the fluid lines (21, 23), at least one further support pillar (57) supporting the MEMS sensor (13), in particular a titanium tube or a titanium column, in particular a further support pillar (57) inserted, in particular welded, into a blind hole bore (59, 61) provided in the MEMS sensor (13), in particular in a frame (39) supporting the channel sections (17) that can be excited to vibration. [3] Measuring device according to claim 1, characterized by , that the MEMS sensor (1, 7, 13) - a lower part (25) produced from a first titanium wafer, in which a recess (29, 31) open towards a top surface of the first wafer is provided for each microfluidic channel (3, 9, 15), the shape of which is the same as the shape of an interior space of the respective channel (3, 9, 15) through which fluid flows during measurement operation, - comprises a top part (27) produced from a second titanium wafer and connected to the bottom part (25), which closes off the interior spaces of the channels (3, 9, 15) formed by the recesses (29, 31) in the bottom part (25) to the outside, - for each channel section (5, 11, 17) that can be excited to vibration, recesses (33, 35, 39) are arranged on both sides of the respective channel section (5, 11, 17), exposing the respective channel section (5, 11, 17) on both sides and extending through the lower part (25) and the upper part (27), and - is mounted on the fluid lines (21, 23) inserted into the openings (19). [4] Measuring device according to claim 1, characterized by , that - the MEMS sensor (1, 7, 13) includes an outer frame (39) which supports the exposed channel sections (5, 11, 17), - each channel (3, 9, 15) comprises an inlet-side and an outlet-side channel end located in the frame (39), and - the openings (19) in the frame (39) are recesses in the frame (39) that are each adjacent to an interior space of one of the channel ends. [5] Measuring device according to claim 4, characterized by , that the frame (39) has, at least in its areas encompassing the openings (19), a frame width which is greater than or equal to the width of the channel section(s) (5, 11, 17) that can be excited to vibration, and / or a frame height which is greater than or equal to the height of the channel section(s) (5, 11, 17) that can be excited to vibration. [6] Measuring device according to claim 1, characterized by , that - the fluid lines (21, 23) have a diameter of 600 µm or greater, in particular from 700 µm to 800 µm, and / or a line wall thickness of 20 µm or greater, in particular from 25 to 100 µm, and / or - the channel sections (5, 11, 17) have a width B of at least one, in particular several hundred µm, a height H of at least one, in particular several hundred µm, and / or a wall thickness in the range of 40 µm to 60 µm. [7] Measuring device according to claim 1, characterized by , that - the measuring device comprises a supporting support (63, 65) for the MEMS sensor (1, 7, 13), in particular the MEMS sensor 1, 7, 13) and at least one further component, in particular electronics (41), a component of the excitation device and / or a component of the measuring device, in particular a device (49) for generating a magnetic field or a counter electrode module (81), in particular a support (65, 67) on which the MEMS sensor (1, 7, 13) is mounted on support pillars (55, 57) comprising freestanding sections of the fluid lines (21, 23), - the support (63, 65) comprises a support area in which a bore leading through the support area is provided for each fluid line (21, 23), and - the fluid lines (21, 23) each terminate in the associated bore or pass through the associated bore. [8] Measuring device according to claim 7, characterized by , that - the support (63) comprises a plate, - the fluid lines (21) run through the bores to a side of the plate facing away from the MEMS sensor (1), where they can be connected to a process line, in particular via process connections (67) provided at their ends, in particular connectors. [9] Measuring device according to claim 7, characterized by, that - the support (65) is designed as part of a line segment, in particular a line segment equipped with a process connection (69) on both the inlet and outlet sides, in particular a flange, in particular a line segment that can be inserted into a process line, - each fluid line (23) serving as a supply line to the MEMS sensor (1, 7, 13) runs through the associated bore in the carrier (65) to an inlet-side inlet area (71) of the line segment, and - each fluid line (23) serving as a discharge line extends through the associated bore in the support (65) to an outlet-side outlet area (73), in particular an outlet area (73) separated from the inlet area (71) by a partition wall (75) provided in the line segment or an outlet area (73) connected to the inlet area (71) via a passage (77). [10] Measuring device according to claim 7, characterized by, that a housing (85), in particular an evacuated housing (85), surrounding the MEMS sensor (1, 7, 13), in particular the MEMS sensor (1, 7, 13) and at least one further component mounted on the carrier (65, 67), in particular an electronics (41), a component of the excitation device and / or a component of the measuring device, is mounted on the carrier (65, 67). [11] Measuring device according to claim 1, characterized by , that - the MEMS sensor (1) comprises two parallel straight channels (3), each comprising a channel section (5) that can be excited to lateral vibrations, - the MEMS sensor (7) comprises a channel (9) with an essentially u-shaped profile, the two parallel legs of which each comprise a channel section (11) that can be excited to lateral vibrations, or - the MEMS sensor (13) comprises a channel (15) with an essentially u- or Ω-shaped profile, which includes a u- or Ω-shaped channel section (17) that can be excited to torsional vibrations.

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