Coriolis mass flow meter and / or density meter

Abstract

Coriolis mass flowmeter and / or density meter (100) comprising: at least two measuring tubes (110) which are bent in the rest position, wherein the measuring tubes (110) have measuring tube center lines which run in pairs mirror-symmetrically to a first mirror plane (Syz) which extends between the measuring tubes (110), wherein the measuring tube center lines each run mirror-symmetrically to a second mirror plane (Sxy) which extends perpendicular to the first mirror plane (Syz); at least one excitation arrangement (140) and at least one sensor arrangement (142); a collector (120) on the inlet side and an outlet side, wherein the measuring tubes (110) are fluidically combined with one of the collectors (120) on the inlet side and the outlet side; a support body (124) which rigidly connects the inlet-side collector (120) and the outlet-side collector (120); and at least one plate-shaped coupler (132, 134) on the inlet side and the outlet side, wherein the measuring tubes (110) are connected to one another in pairs by means of the couplers (132, 134) in order to form an oscillator, wherein the couplers (132, 134) are arranged symmetrically to the first mirror plane (Syz) and in pairs symmetrically to the second mirror plane (Sxy), wherein the excitation arrangement (140) is designed to excite a bending vibration mode between the two measuring tubes (110) of the respective oscillator, wherein the sensor arrangement (142) is adapted to detect oscillations of the respective oscillator, wherein the measuring tube center lines of the measuring tubes (110) of at least one oscillator between the second mirror plane (Sxy) and the collectors (120) each have a first bent section (114), a second bent section (118) and a straight section (116) arranged between the bent sections (114, 118), to which the two bent sections (114, 118) adjoin, wherein the first bent section (114) and the second bent section (118) are bent in opposite directions, wherein the second bent section (118) is arranged on the side of the straight section (116) facing away from the second mirror plane (Sxy), wherein the projection of the measuring tube center line between the intersection point with the second mirror plane (Sxy) and the transition between the straight section (116) and the second bent section (118) onto the second mirror plane (Sxy) Arch height (h) defined,wherein twice the distance between the second mirror plane (Sxy) and the measuring tube center line at the transition between the straight section (116) and the second curved section (118) defines an arc width (w), wherein the quotient of the arc height (h) divided by the arc width (w) defines a relative arc height (h, r ) which is not less than 0.65, where the relative arch height (h r ) is not more than 1.0, wherein the first curved sections (114) between the second mirror plane (Sxy) and the straight section (116) each have a plurality of stiffening bodies (151, 152, 153, 154) which surround the respective measuring tube (110) in a ring shape, wherein at least one of the couplers (132, 134) on the inlet side and the outlet side has a tuning opening surrounded by a closed edge between the measuring tubes (110) connected by the coupler (132, 134) for influencing the oscillation properties of the respective oscillator, wherein the tuning opening in the first mirror plane (Syz) has an extension of at least 70% of the diameter of the measuring tubes (110).

Description

[0001] The present invention relates to a Coriolis mass flowmeter and / or density meter.

[0002] A generic Coriolis mass flowmeter and / or density meter is disclosed, for example, in publication EP 1 296 119 A1. It comprises: at least two measuring tubes that are curved in the rest position, wherein the measuring tubes have measuring tube centerlines that run in pairs mirror-symmetrically to a first mirror plane extending between the measuring tubes, wherein the measuring tube centerlines each run mirror-symmetrically to a second mirror plane extending perpendicular to the first mirror plane; at least one excitation arrangement and at least one sensor arrangement; a collector on the inlet side and outlet side, wherein the measuring tubes are fluidically combined by a collector on the inlet side and outlet side; a carrier body that rigidly connects the inlet-side collector and the outlet-side collector to one another; and two plate-shaped couplers on the inlet side and outlet side,wherein the measuring tubes are connected to one another in pairs by means of the couplers to form an oscillator, wherein the excitation arrangement is configured to excite a bending vibration useful mode between the two measuring tubes of the oscillator, the sensor arrangement is configured to detect vibrations of the oscillator, wherein the measuring tube center lines of the measuring tubes of at least one oscillator between the second mirror plane and the collectors each have a first curved section, a second curved section, and a straight section arranged between the curved sections, to which the two curved sections adjoin, wherein the first curved section and the second curved section are bent in opposite directions, wherein the second curved section is arranged on the side of the straight section facing away from the second mirror plane,wherein the first curved section between the second mirror plane and the straight section has a stiffening body which surrounds the measuring tube in a ring shape.,

[0003] Coriolis mass flowmeters and / or density meters are further described in WO-A 01 / 33174, WO-A 00 / 57141, WO-A 98 / 07009, US-A 5796001, US-A 4781069, EP-A 1001254, EP-A 553939.

[0004] DE 10 2011 010 178 A1 discloses a Coriolis mass flowmeter with at least four curved measuring tubes, which are arranged in pairs in one plane and oscillate against the measuring tubes in the other plane, wherein all four measuring tubes are fluidically combined on the inlet and outlet sides with a collector.

[0005] US 2011 / 0 036 179 A1 discloses a Coriolis mass flowmeter with two measuring tubes for measuring the flow of multiphase media by means of excitation above a decoupling frequency of the medium.

[0006] WO 2012 / 136 671 A1 discloses a Coriolis mass flowmeter and / or density meter with two bent measuring tubes which are coupled on the inlet side and outlet side with coupler elements.

[0007] Curved measuring tubes are typically excited to flexural vibrations in the so-called useful mode. These flexural vibrations induce Coriolis forces in the flowing medium, resulting in the excited flexural vibrations of the useful mode being superimposed with oscillations in the Coriolis mode at the same frequency. In curved measuring tubes, thermally induced expansion causes virtually no or only very minor mechanical stresses in the measuring tube itself or in a connected pipeline. Furthermore, the measuring tubes can be designed with a wide extension and thus, despite a relatively short installation length, can be excited to the oscillation amplitudes required for measuring flow and / or density even with relatively low excitation power.

[0008] The two parallel, essentially identically shaped measuring tubes according to the measuring devices described in US-A 57 96 001 and WO-A 01 / 33 174 are essentially continuously curved, i.e. they are practically nowhere straight. In contrast, the measuring tubes of the measuring devices shown, for example, in US-A 53 01 557, WO-A 00 / 57 141, WO-A 01 / 33 174 each have at least two straight tube segments that are connected to one another via an arc-shaped, in particular circular arc-shaped, tube segment. Measuring tubes curved in this way with straight tube segments are distinguished, in particular, from continuously curved measuring tubes, in that they can be manufactured cost-effectively using very simple bending tools.

[0009] Preferably, the measuring tubes are vibrated during operation at a natural, instantaneous resonance frequency. Since the natural resonance frequency depends on the instantaneous density of the fluid, commercially available Coriolis mass flowmeters can be used to measure not only the mass flow but also, for example, the density of flowing fluids.

[0010] To detect vibrations of the measuring tubes, the measuring devices comprise a sensor arrangement with at least one inlet-side and at least one outlet-side vibration sensor, which can in particular be an electrodynamic sensor. Due to the superposition of the wanted and Coriolis modes, the vibrations of the measuring tubes detected by the sensor arrangement on the inlet and outlet sides exhibit a flow-dependent phase difference, which can be determined using signals from the electrodynamic sensors.

[0011] Coriolis flowmeters and / or density meters can be sensitive to temperature influences and media pressure. To compensate for such temperature-related interference, Coriolis mass flowmeters and / or density meters typically also include at least one temperature sensor, for example, for measuring the temperature of the measuring tube or the surroundings of the measuring tube.

[0012] The cross-sensitivity to media pressure is mentioned in the following documents, among others: EP 1 296 119 A1, US-A 53 01 557, WO-A 95 / 16 897, and WO-A 98 / 07 009. This cross-sensitivity of the measuring devices to pressure can be explained, among other things, by the fact that the measuring tubes exhibit a stiffness that depends on the media pressure. To ensure measurement errors of no more than ±0.15% of the actual mass flow or the actual density, even with fluctuating media pressure, measures to reduce the pressure dependence of the measurement signals are therefore required.

[0013] To solve this problem, US-A-53 01 557, for example, proposes using measuring tubes with comparatively thicker walls. While this reduces the pressure dependence, the mass of the measuring tube simultaneously increases, so that the relative contribution of the medium to the mass of the filled measuring tube decreases, thereby reducing the sensitivity of the density measurement. Furthermore, the measuring tube becomes stiffer overall, so that a higher excitation power is required to achieve the same oscillation amplitudes.

[0014] Another possibility for reducing the measuring device's cross-sensitivity to pressure is described in WO-A 98 / 07009 and WO-A 95 / 16897. It is proposed to determine the medium pressure based on the resonance frequencies of two different vibration modes and to take this into account when determining the mass flow rate. This requires an additional exciter and increased computing power for measuring the measured values.

[0015] Publication EP 1 296 119 A1 discloses stabilizing the measuring tubes using local stiffeners to reduce the influence of internal pressure on the bending vibrations. The relatively small additional mass of the stiffeners barely affects the sensitivity to the primary measured variables of mass flow and density. This approach is fundamentally interesting, but still leaves room for improvement.

[0016] Based on the cited prior art, the invention is therefore based on the object of providing an improved Coriolis mass flowmeter and / or density meter whose measuring tubes are easy to manufacture and whose cross-sensitivity to the internal pressure or to changes in the internal pressure can be kept low.

[0017] The object is achieved by the Coriolis mass flow meter and / or density meter according to independent patent claim 1.

[0018] The Coriolis mass flowmeter and / or density meter according to the invention comprises at least two measuring tubes which are curved in the rest position, wherein the measuring tubes have measuring tube center lines which run in pairs mirror-symmetrically to a first mirror plane extending between the measuring tubes, wherein the measuring tube center lines each run mirror-symmetrically to a second mirror plane extending perpendicular to the first mirror plane; at least one excitation arrangement and at least one sensor arrangement; a collector on the inlet side and outlet side, wherein the measuring tubes are fluidically combined with one of the collectors on the inlet side and outlet side; a carrier body which rigidly connects the inlet-side collector and the outlet-side collector; and at least one plate-shaped coupler on the inlet side and outlet side,wherein the measuring tubes are connected to one another in pairs by means of the couplers to each form an oscillator, wherein the couplers are arranged symmetrically to the first mirror plane and in pairs symmetrically to the second mirror plane, wherein the excitation arrangement is configured to excite a bending vibration useful mode between the two measuring tubes of the oscillator, wherein the sensor arrangement is configured to detect oscillations of the oscillator, wherein the measuring tube center lines of the measuring tubes of at least one oscillator between the second mirror plane and the collectors each have a first curved section, a second curved section, and a straight section arranged between the curved sections, to which the two curved sections adjoin, wherein the first curved section and the second curved section are bent in opposite directions,wherein the second curved section is arranged on the side of the straight section facing away from the second mirror plane, wherein the projection of the measuring tube center line between the intersection with the second mirror plane and the transition between the straight section and the second curved section onto the second mirror plane defines an arc height, wherein twice the distance between the second mirror plane and the measuring tube center line at the transition between the straight section and the second curved section defines an arc width, wherein the quotient of the arc height divided by the arc width defines a relative arc height that is not less than 0.65, wherein the relative arc height is not more than 1.0, wherein the first curved sections between the second mirror plane and the straight section each have a plurality of stiffening bodies that surround the respective measuring tube in a ring shape,wherein at least one of the couplers, on the inlet side and on the outlet side, has a tuning opening surrounded by a closed edge between the measuring tubes connected by the coupler for influencing the oscillation properties of the oscillator, wherein the tuning opening in the first mirror plane has an extension of at least 70% of the diameter of the measuring tubes.

[0019] In a further development of the invention, a first coupler, which is closest to the second mirror plane, has a center plane which is spaced from the measuring tube center line at the transition between the straight section and the second curved section by no more than half, in particular no more than one third, preferably no more than one quarter of the outer diameter of the measuring tubes connected to the coupler.

[0020] In a further development of the invention, the first coupler is arranged in the second curved section.

[0021] In a further development of the invention, the measuring tube center line in the second straight section has an angle of not less than 60°, in particular not less than 70°, to a normal vector to the second mirror plane.

[0022] In a further development of the invention, the first curved sections between the second mirror plane and the straight section each have at least three, in particular at least four stiffening bodies which surround the respective measuring tube in a ring shape.

[0023] In a further development of the invention, the stiffening bodies have a thickness in the direction of the measuring tube center line which is not more than a quarter, in particular not more than an eighth of the outer diameter of the measuring tube.

[0024] In a further development of the invention, the stiffening bodies have a thickness in the radial direction which is at least one, in particular at least two wall thicknesses of the measuring tube.

[0025] In a further development of the invention, the stiffening bodies are arranged in pairs symmetrically to the first and / or second mirror plane.

[0026] In a further development of the invention, the Coriolis mass flowmeter and / or density meter has a flow calibration factor (calf) for the mass flow as a function of an oscillation behavior of the oscillator, wherein the flow calibration factor (calf) has a pressure dependence (d calf / dp) for which |1 / calf* d calf / dp| < 70 ppm / bar applies.

[0027] In a further development of the invention, the Coriolis mass flowmeter and / or density meter has a density calibration factor for the density (crho) as a function of at least one natural frequency (f1) of the oscillator, wherein the density calibration factor (crho) has a pressure dependence (d crho / dp) for which |1 / crho* d crho / dp| < 60 ppm / bar, in particular < 40 ppm / bar.

[0028] In a further development of the invention, the collectors provided on the inlet and outlet sides are designed to be so stable that they fulfill the functionality of a coupler.

[0029] In a further development of the invention, the tuning opening in the first mirror plane has an extension of at least 70% of the diameter of the measuring tubes.

[0030] In a further development of the invention, at least two couplers of a measuring tube pair connected by the couplers each have such a tuning opening on the inlet side and on the outlet side.

[0031] The invention will now be explained in more detail with reference to the exemplary embodiments illustrated in the drawings. It shows: Fig. 1: a schematic side view of a first embodiment of a Coriolis mass flowmeter and / or density meter according to the invention; Fig. 2: a side view of a detail of the Fig. 1 illustrated embodiment; Fig. 3: a coordinate system to explain the symmetries of the Coriolis mass flowmeter and / or density meter according to the invention.

[0032] The Fig. 1 and Fig.The exemplary embodiment of a Coriolis mass flowmeter and / or density meter 100 according to the invention shown in Figure 2 comprises a pair of bent measuring tubes 110. The measuring tubes 110 extend between an inlet-side collector 120 and an outlet-side collector 120 and are firmly connected to them, for example by rolling, brazing, or welding. A solid support tube or support body 124 extends between the collectors 120 and is firmly connected to both collectors, thereby rigidly coupling the collectors 120 to one another. The support body 124 has openings 126 on its upper side through which the measuring tubes 110 are guided from the collectors 120 out of the support body 124 and back again.

[0033] The collectors 120 each have a flange 122 at their ends, by means of which the Coriolis mass flowmeter and / or density meter is to be installed in a pipeline. A mass flow is to be guided through the pipelines 110 through central openings 123 in the flanges 122 in order to measure the mass flow and / or its density.

[0034] Before the detailed structure and operation of the Coriolis mass flowmeter and / or density meter 100 according to the invention are explained further, Fig. 3 some symmetry properties are presented. In Fig.Figure 3 shows the measuring tube centerlines 112a, 112b of the two measuring tubes 110, which form the oscillator. The measuring tube centerlines 112a, 112b run symmetrically to a first mirror plane Syz, which runs between the measuring tubes. The measuring tube centerlines also run symmetrically to a second mirror plane Sxy, which runs perpendicular to the first mirror plane Syz. The vertices of the measuring tubes and the measuring tube centerlines lie in the second mirror plane.

[0035] The measuring tube axes 112a, 112b preferably run in planes that are parallel to the first mirror plane.

[0036] With respect to a third plane Szx, which runs perpendicular to the first mirror plane and to the second mirror plane, and in which the measuring tube axes 112a, 112b run in the collectors, there is no symmetry of the measuring tubes.

[0037] The intersection line between the first mirror plane Syz and the third plane defines a Z-axis of a coordinate system of the Coriolis mass flowmeter and / or density meter. The intersection line between the second mirror plane Sxy and the third plane Szx defines an X-axis of the coordinate system, and the intersection line between the first mirror plane Syz and the second mirror plane defines the Y-axis of the coordinate system. With the coordinates defined in this way, we return to Fig. 1 and Fig. 2 to.

[0038] The measuring tubes 110 form an oscillator in pairs, which is to be excited in particular in a bending vibration mode in which the measuring tubes oscillate in antiphase to each other in the X direction.

[0039] To influence the vibration properties, the measuring tubes 110 are connected on the inlet and outlet sides, respectively, with couplers 132, 134. The position of the two inner couplers 132, i.e., those which are furthest away from the corresponding collector 120 on the inlet and / or outlet sides, determines a free oscillation length of an oscillator formed by the two measuring tubes 110. This free oscillation length has a significant influence on the bending vibration mode of the oscillator, in particular on its natural frequency, with which the oscillator should preferably be excited.

[0040] Outer couplers 134, each arranged between the inner node plates 132 and the collectors 120, serve in particular to define further vibration nodes in order, on the one hand, to reduce the maximum mechanical stresses on the vibrating measuring tubes and, on the other hand, to minimize the coupling of vibration energy into a pipeline in which the Coriolis mass flowmeter and / or density meter is mounted, or the coupling of parasitic vibrations from the pipeline. The couplers preferably have tuning openings surrounded by a circumferential edge in the first mirror plane, through which the coupling of vibration energy is to be further minimized. The couplers are preferably arranged symmetrically to the first mirror plane and in pairs symmetrically to the second mirror plane.

[0041] To excite bending vibrations of the measuring tubes in the X direction, an excitation arrangement 140 is provided between the two measuring tubes 110—relative to the longitudinal direction or the Z axis in the center of the Coriolis mass flowmeter and / or density meter 100—for example, an inductive excitation arrangement each comprising, for example, a moving coil on one measuring tube and a plunger on the opposite measuring tube. The oscillator formed by the two measuring tubes is preferably excited at its current natural frequency. To detect the vibrations of the measuring tubes, sensor arrangements 142 are provided in the longitudinal direction symmetrically to the excitation arrangements 140, each designed as an inductive arrangement with a moving coil on one tube and a plunger on the other tube. Details of this are known to those skilled in the art and need not be explained in detail here.

[0042] In the Fig.In the embodiment shown in Figure 1, the sensor assemblies 142 are arranged outside an area enclosed by the measuring tubes 110 and the support body 124. They are arranged on the inside of a measuring tube bend extending through the vertices of the measuring tubes. Of course, the sensor assemblies can also be arranged within the enclosed area, for example, to achieve a somewhat more compact design.

[0043] The measuring tubes 110 each have two first bent sections 114 that are symmetrical to one another with respect to the second mirror plane and that adjoin one another in the second mirror plane. Each of the first bent sections 114 has a bending angle of approximately 80°, wherein the radius of curvature of the tube center axis in the first bent sections here is no less than eight, in particular approximately nine, tube radii. Adjoining the first bent section 114 is a straight section 116, which in turn is adjoined by a second bent section 118, the radius of curvature of which here is approximately two-thirds of the radius of curvature of the first bent section 114.

[0044] The second curved sections 118 each extend through one of the openings 126 in the carrier body 124 and open into one of the collectors 120.

[0045] The first curved sections 114 each have four annular stiffening bodies 151, 152, 153, 154, which are distributed over the first curved section 114. The distribution does not have to be uniform, as is the case here. The specific distribution can be varied if necessary to optimize the cross-sensitivity of the measured variables mass flow and / or density to pressure.

[0046] The following considerations must be taken into account when positioning the inner couplers 132. On the one hand, it is advantageous if the measuring tubes 110 have a large free oscillation length. For this purpose, the measuring tubes are led out of the support body 124 in the second curved section 118, with the free oscillation length increasing with increasing arc height. To optimize the free oscillation length, it would be advisable to position the inner coupler, which limits the free oscillation length, as low as possible. Part of the gained arc height is "wasted" again - in the illustrated embodiment, approximately a quarter of the arc height, to ensure that at most only a short part of the second curved section 118 runs above the first coupler 132.Investigations in connection with the present invention have shown that the pressure dependence of the density measurement can be reduced if the proportion of the second bent sections 118 above the first coupler 132 is not too large, as shown in . Fig. 2. The coupler spacing angle α k1 , measured from the center of the radii of curvature of the measuring tube center axis, is a measure of the distance of the first coupler 132 from the transition between the straight section 116 and the second curved section 118. The coupler distance angle α k1should not exceed 10° and, in the exemplary embodiment, has a value of approximately 5° to 6°. In other words, the distance between the coupler center plane of the first coupler 132 and the transition between the straight section 116 and the second curved section 118 should not exceed half the outer diameter of the measuring tube. In the exemplary embodiment shown, this distance is a good quarter of the outer diameter.

[0047] The Coriolis mass flowmeter and / or density meter according to the invention has a high sensitivity for the precise measurement of density and mass flow due to the measuring tube geometry according to the invention, wherein the cross-sensitivities to static pressure associated with the measuring tube geometry are eliminated by the described measures, such as the position of the first couplers 132 and the stiffening bodies 151, 152, 153, 154 in the first curved section 114. In this way, the pressure dependence of the density measurement is significantly reduced. The results for this are given in Table 1. Therein, the term "calf" refers to a calibration factor, proportionality factor, for determining the mass flow from the phase difference between the sensors 142 of the sensor arrangement. Table 1: Inner pipe diameter [mm] 15,2 28,0 43,1 68,9 Flow calibration factor (Calf) 0.90 0,50 0,50 0,75 Relative pressure dependence of density calibration [ppm / bar] -34 -27.8 -27 -20 Relative pressure dependence of the Calf [ppm / bar] -38,3 -31,2 -51.7 -43,5 Relative pressure dependence of density calibration without stiffening rings [ppm / bar] -123,5 -50,4 -50,7 -53 Relative pressure dependence of the calf without stiffening rings [ppm / bar] -161,4 -87,6 -190,3 -80,9

Claims

[1] Coriolis mass flowmeter and / or density meter (100) comprising: at least two measuring tubes (110) which are bent in the rest position, wherein the measuring tubes (110) have measuring tube center lines which run in pairs mirror-symmetrically to a first mirror plane (Syz) which extends between the measuring tubes (110), wherein the measuring tube center lines each run mirror-symmetrically to a second mirror plane (Sxy) which extends perpendicular to the first mirror plane (Syz); at least one excitation arrangement (140) and at least one sensor arrangement (142); a collector (120) on the inlet side and an outlet side, wherein the measuring tubes (110) are fluidically combined with one of the collectors (120) on the inlet side and the outlet side; a support body (124) which rigidly connects the inlet-side collector (120) and the outlet-side collector (120); and at least one plate-shaped coupler (132, 134) on the inlet side and the outlet side, wherein the measuring tubes (110) are connected to one another in pairs by means of the couplers (132, 134) in order to form an oscillator, wherein the couplers (132, 134) are arranged symmetrically to the first mirror plane (Syz) and in pairs symmetrically to the second mirror plane (Sxy), wherein the excitation arrangement (140) is designed to excite a bending vibration mode between the two measuring tubes (110) of the respective oscillator, wherein the sensor arrangement (142) is adapted to detect oscillations of the respective oscillator, wherein the measuring tube center lines of the measuring tubes (110) of at least one oscillator between the second mirror plane (Sxy) and the collectors (120) each have a first bent section (114), a second bent section (118) and a straight section (116) arranged between the bent sections (114, 118), to which the two bent sections (114, 118) adjoin, wherein the first bent section (114) and the second bent section (118) are bent in opposite directions, wherein the second bent section (118) is arranged on the side of the straight section (116) facing away from the second mirror plane (Sxy), wherein the projection of the measuring tube center line between the intersection point with the second mirror plane (Sxy) and the transition between the straight section (116) and the second bent section (118) onto the second mirror plane (Sxy) Arch height (h) defined,wherein twice the distance between the second mirror plane (Sxy) and the measuring tube center line at the transition between the straight section (116) and the second curved section (118) defines an arc width (w), wherein the quotient of the arc height (h) divided by the arc width (w) defines a relative arc height (h, r ) which is not less than 0.65, where the relative arch height (h r ) is not more than 1.0, wherein the first curved sections (114) between the second mirror plane (Sxy) and the straight section (116) each have a plurality of stiffening bodies (151, 152, 153, 154) which surround the respective measuring tube (110) in a ring shape, wherein at least one of the couplers (132, 134) on the inlet side and the outlet side has a tuning opening surrounded by a closed edge between the measuring tubes (110) connected by the coupler (132, 134) for influencing the oscillation properties of the respective oscillator, wherein the tuning opening in the first mirror plane (Syz) has an extension of at least 70% of the diameter of the measuring tubes (110). [2] Coriolis mass flowmeter and / or density meter (100) according to claim 1, wherein in each case a first coupler (132) which is closest to the second mirror plane (Sxy) has a center plane which is not more than half, in particular not more than one third, preferably not more than one quarter of the outer diameter d a the measuring tubes (110) connected to the coupler (132) are spaced from the transition between the straight section and the second curved section at the measuring tube centerline. [3] The Coriolis mass flowmeter and / or density meter (100) of claim 2, wherein the first coupler (132) is disposed in the second bent portion (118). [4] Coriolis mass flow meter and / or density meter (100) according to one of the preceding claims, wherein the measuring tube center line in the straight section (116) has an angle of not less than 60°, in particular not less than 70°, to a normal vector to the second mirror plane (Sxy). [5] Coriolis mass flowmeter and / or density meter (100) according to claim 2, wherein the first curved sections (114) between the second mirror plane (Sxy) and the straight section (116) each have at least three, in particular at least four stiffening bodies (151, 152, 153, 154) which surround the respective measuring tube (110) in a ring shape. [6] Coriolis mass flowmeter and / or density meter (100) according to one of the preceding claims, wherein the stiffening bodies (151, 152, 153, 154) have a thickness in the direction of the measuring tube center line which is not more than one quarter, in particular not more than one eighth of the outer diameter of the measuring tube (110). [7] Coriolis mass flowmeter and / or density meter (100) according to one of the preceding claims, wherein the stiffening bodies (151, 152, 153, 154) have a thickness in the radial direction which is at least one, in particular at least two wall thicknesses of the measuring tube (110). [8] Coriolis mass flowmeter and / or density meter (100) according to one of the preceding claims, wherein the stiffening bodies (151, 152, 153, 154) are arranged in pairs symmetrically to the first (Syz) and / or second mirror plane (Sxy). [9] Coriolis mass flow meter and / or density meter (100) according to one of the preceding claims, which has a flow calibration factor (calf) for the mass flow as a function of an oscillation behavior of the oscillator, wherein the flow calibration factor (calf) has a pressure dependence (d calf / dp) for which the following applies: |1 / calf * d calf / dp| < 70 ppm / bar. [10] Coriolis mass flowmeter and / or density meter (100) according to one of the preceding claims, which has a density calibration factor for the density (crho) as a function of at least one natural frequency (f1) of the oscillator, wherein the density calibration factor (crho) has a pressure dependence (d crho / dp) for which the following applies: |1 / crho* d crho / dp| < 60 ppm / bar, in particular < 40 ppm / bar. [11] Coriolis mass flow meter and / or density meter (100) according to one of the preceding claims, wherein the collectors (120) provided on the inlet side and the outlet side are designed to be stable in such a way that they fulfill the functionality of a coupler. [12] Coriolis mass flowmeter and / or density meter (100) according to claim 1, wherein at least two couplers (132, 134) of a measuring tube pair (110) connected by the couplers (132, 134) each have such a tuning opening on the inlet side and on the outlet side.

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