ARRANGEMENT OF ULTRASOUND TRANSMITTERS, CLAMP-ON ULTRASOUND MEASURING DEVICE WITH SUCH ARRANGEMENT AND METHOD FOR SETTING THE ULTRASOUND MEASURING DEVICE

Description

[0001] The invention relates to an arrangement of ultrasonic transducers, a clamp-on ultrasonic measuring device for measuring a quantity of a medium located in a measuring tube with such an arrangement, and a method for adjusting the ultrasonic measuring device.

[0002] Ultrasound transducers of clamp-on ultrasonic measuring devices are used to transmit and receive ultrasonic signals in order to make a statement about a property of a medium located in a measuring tube, for example from a signal transit time of the ultrasonic signals or a transit time difference of two oppositely traveling ultrasonic signals, see for example DE10254053A1.

[0003] US Patent 5,546,813 A discloses an ultrasonic measuring device which, through a multitude of ultrasonic transducer pairs with crossed sound paths, obtains more information about the flow profile of the medium.

[0004] The problem with typical clamp-on ultrasonic measuring devices and the previously mentioned ultrasonic measuring devices is that ultrasonic signals cause signal reflections at various interfaces, which also reach a receiving ultrasonic transducer and superimpose on the actual measurement signal.

[0005] The object of the invention is therefore to minimize the influence of such disruptive signal reflections.

[0006] The problem is solved by an arrangement according to independent claim 1, by a clamp-on ultrasonic measuring device according to independent claim 7, and by a method according to independent claim 8.

[0007] An arrangement of ultrasonic transducers of a clamp-on ultrasonic measuring device according to the invention for measuring a measured quantity of a medium flowing through a measuring tube, wherein the ultrasonic transducers are arranged on the measuring tube, comprises: at least one pair of ultrasonic transducers arranged on the measuring tube for, in particular, the mutual transmission and reception of ultrasonic signals, wherein the ultrasonic transducers in a measuring arrangement have an axial spacing from each other with respect to a measuring tube axis, wherein the ultrasonic transducers each have a transducer device with a transducer longitudinal axis for generating and acquiring ultrasonic signals and a coupling element for transmitting the ultrasonic signals between the transducer device and the measuring tube, wherein the transducer devices are each acoustically and mechanically connected to an associated coupling element via a transducer-side coupling surface of the coupling element, wherein the transducer devices each have a side facing the associated coupling element with a contact surface area, wherein the contact surface areas each have a centroid of the area area, wherein an transmitting transducer device is configured toto generate an ultrasonic signal field, which ultrasonic signal field in the coupling body has a first longitudinal axis, in particular parallel to the transducer longitudinal axis, wherein the ultrasonic signal field in the medium has an opening angle in a measuring tube longitudinal section plane through the centroids of the area areas, wherein the first longitudinal axis defines a reference signal path with a reference arrangement for the ultrasonic transducers and is part of this reference signal path and has a longitudinal axis angle to a normal of a measuring tube wall, wherein the reference signal path defines an axial reference distance between the centroids of the area areas with respect to the reference arrangement, wherein in the measuring arrangement a measuring path runs between the centroids of the area areas, wherein the axial arrangement distance is dimensioned through the centroids of the area areas, wherein the coupling bodies are each acoustically and mechanically connected to the measuring tube via a coupling surface.where the arrangement distance is smaller than the reference distance, and where a target difference between the reference distance and the arrangement distance depends on at least the following characteristic: the opening angle of the ultrasonic signal field in the medium.

[0008] The opening angle can be calculated or specified, for example, using a formula that incorporates the wavelength of the ultrasound signal in the medium and the side length of the transducer element. A person skilled in the art may also use other or additional measured parameters.

[0009] For example, the opening angle can also be determined by calibration measurements.

[0010] It has been shown that by using a measurement setup with a spacing smaller than the reference distance, interfering influences, such as signal reflections, are reduced, thus simplifying signal evaluation.

[0011] A contact area can simply be a single contact surface, as in the case of a one-piece piezoelectric element. The contact surface can take on a shape such as a circle or a regular polygon, but is not limited to this. The contact area can also be spanned by several non-connected contact surfaces. The centroid of the contact area can also lie outside of a single contact surface.

[0012] The converter device can be, for example, disc-shaped. It can also be, for example, block-shaped. The converter device can be a single piece or composed of several components.

[0013] According to the invention, an ultrasonic signal causes echo paths in the measuring tube wall which have a common endpoint with the reference signal path, wherein a receiving ultrasonic transducer in the measuring arrangement filters out at least a first echo path on a side of the measuring tube facing the receiving ultrasonic transducer with two reflections in the measuring tube wall and in particular at least a second echo path with four reflections in the measuring tube wall.

[0014] In this way, a significant source of interference is eliminated, and the measurement characteristics of the setup are improved. Eliminating an echo path does not preclude the possibility that peripheral regions of echo signals are picked up by a receiving ultrasonic transducer. The term echo path refers to a central region of maximum echo amplitude within an echo signal.

[0015] In one embodiment, the opening angle in the medium is defined by an amplitude drop of 20 decibels relative to a maximum amplitude. wherein the reference path in the medium has a first angle to the normal of the measuring tube wall, wherein the measuring path in the medium has a second angle to the normal of the measuring tube wall, wherein the magnitude of the second angle is smaller than the first angle, wherein an angle difference is the opening angle multiplied by a factor F, wherein F is at most 1.5 and in particular at most 1.2 and preferably at most 1.

[0016] It has been shown that in this way a receiving ultrasound transducer in a peripheral area of ​​the ultrasound signal field receives a sufficiently good ultrasound signal and benefits from a minimization of interference.

[0017] In one embodiment, the target difference is at least 1 millimeter, and in particular at least 2 millimeters, and preferably at least 3 millimeters. This ensures a minimum effect of the invention.

[0018] In one embodiment, the opening angle of the ultrasound signal field is smaller than 2 times the first angle.

[0019] In one embodiment, the converter device has at least one piezoelectric element.

[0020] In one embodiment, the opening angle in the medium can be calculated using the following formula: Ö = arcsin 0.87 * W / S with W as the wavelength of a central frequency of the ultrasound signal in the medium and S as the side length of the transducer device in a measuring tube longitudinal section plane.

[0021] A clamp-on ultrasonic measuring device according to the invention for measuring a measured quantity of a medium located in a measuring tube comprises an arrangement according to the invention, and an electronic measuring / operating circuit for operating the ultrasonic transducers and for providing and outputting measured values ​​of the measured quantity.

[0022] In a method according to the invention for setting up an ultrasonic measuring device according to the invention, at least the following quantities are used in a first method step to determine the reference signal path or reference distance: at least one sound velocity of coupling body, measuring tube wall, medium, angle between first longitudinal axis and a normal to the measuring tube wall, a thickness of a measuring tube wall, a diameter of the measuring tube, number of ultrasonic signal traverses in the measuring tube, wherein in a second process step at least one of the following quantities is used to determine the target difference: opening angle in the medium, wherein in a third process step the ultrasonic transducers of a pair are arranged on the measuring tube according to the results of the first process step and the second process step.

[0023] In one embodiment, the electronic measuring / operating circuit performs the first process step and the second process step and provides an operator with information to execute the third process step.

[0024] In one embodiment, the operator of the electronic measuring / operating circuit provides information for executing the first process step.

[0025] The invention will be described below using exemplary embodiments. Fig. 1 outlines exemplary arrangements of an ultrasonic transducer pair on a measuring tube; Fig. 2 outlines an exemplary clamp-on ultrasonic measuring device; Fig. 3 outlines an exemplary method according to the invention for setting up a clamp-on ultrasonic measuring device.

[0026] Fig. 1Figure 1 outlines the structure and function of two arrangements 2 of a pair of exemplary clamp-on ultrasonic transducers 10, which are arranged on the outside of a measuring tube 20. Each ultrasonic transducer has a disc-shaped transducer device 11 and a coupling body 12, wherein the transducer device is acoustically and mechanically connected via a contact surface area 11.1 to a transducer-side coupling surface 12.1 of the coupling body. The contact surface areas each have a centroid 11.11.

[0027] A contact area can simply be a single contact surface, as in the case of a one-piece piezoelectric element. The contact surface can take on a shape such as a circle or a regular polygon, but is not limited to this. The contact area can also be spanned by several non-connected contact surfaces. The centroid of the contact area can also lie outside of a single contact surface.

[0028] The converter device can, for example, also be block-shaped. The converter device can be a single piece or composed of several components.

[0029] A first arrangement corresponds to a reference arrangement 2.1, and a second arrangement corresponds to a measuring arrangement 2.2 according to the invention. The reference arrangement corresponds to an arrangement according to the prior art, wherein a receiving ultrasonic transducer picks up an ultrasonic signal along a reference signal path 2.11. The reference signal path is characterized in that it runs along a first longitudinal axis of an ultrasonic signal field in the coupling body, i.e., along a region of maximum ultrasonic signal amplitude.

[0030] Typically, the first longitudinal axis 13.1 runs as shown along a converter longitudinal axis 11.2 starting from the area centroid 11.11.

[0031] The reference arrangement has an axial reference distance 2.12, which is dimensioned parallel to a measuring tube axis 21 between the centroids 11.11 of the contact surfaces of the transducer devices of the ultrasonic transducers. Accordingly, a measuring arrangement has an axial arrangement distance 2.22.

[0032] One problem with the reference setup is that not only the ultrasound signal itself, but also reflections of the ultrasound signal at various interfaces reach a receiving ultrasound transducer via echo paths, thus interfering with the ultrasound signal. Echo paths are illustrated by the dashed lines, where two reflections occur at interfaces in a measuring tube wall 22 of the measuring tube. Other echo paths with more than two reflections also exist.

[0033] According to the invention, the axial arrangement distance 2.22 is smaller in magnitude than the reference distance 2.21, wherein a target difference between reference distance and arrangement distance depends on at least the following feature: opening angle of the ultrasonic signal field in the medium.

[0034] In this way, the influence of interference such as reflected ultrasound signals via echo paths can be reduced. The relevance of echo paths with respect to their interference characteristics increases with increasing opening angle of the ultrasound signal field. The opening angle of the ultrasound signal field in the medium is a suitable, simple parameter, since the ultrasound signal field in the medium is essentially defined by a far-field characteristic. A formula can be used, for example, to measure the opening angle, incorporating a wavelength of the ultrasound signal in the medium and a side length of the transducer element. A person skilled in the art can also use other or additional measured quantities. For example, the opening angle can also be determined through calibration measurements.

[0035] In one embodiment, the opening angle 13.2 in the medium is defined by an amplitude drop of 20 decibels relative to a maximum amplitude, wherein the reference signal path 2.11 in the medium has a first angle 2.13 with respect to the normal of the measuring tube wall, and wherein the measuring path 2.21 in the medium has a second angle 2.23 with respect to the normal of the measuring tube wall, the magnitude of which of the second angle is smaller than that of the first angle. The angular difference between the first angle and the second angle is the opening angle multiplied by a factor F, where F is at most 1.5, and in particular at most 1.2, and preferably at most 1. It has been shown that in this way a receiving ultrasonic transducer receives a sufficiently strong ultrasonic signal in a marginal region of the ultrasonic signal field and benefits from a minimization of interference.

[0036] In one embodiment, the target difference is at least 1 millimeter, and in particular at least 2 millimeters, and preferably at least 3 millimeters. This ensures a minimum effect of the inventive effect.

[0037] In one design, it is as dazzling as in Fig. 1 The instrument depicts a receiving ultrasonic transducer in the measuring arrangement emitting at least one first echo path 3.1 on a side of the measuring tube facing the receiving ultrasonic transducer, with two reflections in the measuring tube wall, and in particular at least one second echo path (not shown) with four reflections in the measuring tube wall. In this way, a significant source of interference is eliminated and the measurement characteristics of the measuring arrangement are improved.

[0038] The converter device 11 can, for example, have at least one piezoelectric element 11.3.

[0039] The opening angle 11.3 in the medium can be calculated or measured using the following formula: Opening angle = arcsin(0.87 * W / S) with W as the wavelength of a central frequency of the ultrasound signal in the medium and S as the side length of the transducer device in a longitudinal section of a measuring tube and defined by an amplitude drop of 20 decibels relative to a maximum amplitude.

[0040] For a reference arrangement as well as a measuring arrangement with more than one ultrasonic signal traverse in the measuring tube, what has been said so far applies, whereby the target difference is multiplied by a factor corresponding to the number of traverses.

[0041] Fig. 2Figure 1 sketches a schematic example of a clamp-on ultrasonic measuring device with a measuring tube 20 and two ultrasonic transducers 10 in a single-crosshead or double-crosshead arrangement (dashed lines) and an electronic measuring / operating circuit 30 for operating the ultrasonic transducers and for providing and outputting measured values ​​of a measured quantity. The measured quantity can be, for example, the speed of sound or the flow velocity or volumetric flow rate of a medium in the measuring tube. Clamp-on ultrasonic measuring devices with more than two crossheads can also be used.

[0042] Fig. 3 outlines a method 100 according to the invention for adjusting the clamp-on ultrasonic measuring device or the arrangement of the ultrasonic transducers on the measuring tube.

[0043] In a first process step 101, at least the following quantities are used to determine the reference signal path or reference distance: at least one sound velocity of coupling body, measuring tube wall, medium, respectively.

[0044] Angle between first longitudinal axis and a normal to the measuring tube wall, thickness of a measuring tube wall, diameter of the measuring tube, number of ultrasonic signal traverses in the measuring tube.

[0045] By applying Snell's law of refraction, the course of the reference signal path can therefore be determined.

[0046] In a second process step 102, at least the opening angle in the medium is used to determine the target difference, wherein in a third process step 103 the ultrasonic transducers of a pair are arranged on the measuring tube according to the results of the first process step and the second process step.

[0047] In one embodiment of the procedure, the electronic measuring / operating circuit 30 performs the first procedure step and the second procedure step and provides an operator with information to execute the third procedure step.

[0048] In one embodiment of the process, the operator of the electronic measuring / operating circuit provides 30 pieces of information required to execute the first process step. This information includes, for example, the typical speed of sound of the medium.

[0049] In this way, the measuring arrangement according to the invention can be set up easily and safely. Reference symbol list

[0050] 1 Clamp-on ultrasonic measuring device 2 Arrangement 2.1 Reference arrangement 2.11 Reference signal path 2.12 Axial reference distance 2.13 First angle 2.2 Measuring arrangement 2.21 Measuring path 2.22 Axial arrangement distance 2.23 Second angle 3.1 First echo path 10 Ultrasonic transducer 11 Transducer device 11.1 Contact surface 11.11 Area area centroid 11.2 Transducer longitudinal axis 11.3 Piezoelectric element 12 Coupling body 12.1 Transducer-side coupling surface 12.2 Measuring tube-side coupling surface 13 Ultrasonic signal field 13.1 First longitudinal axis 13.2 Opening angle in the medium 20 Measuring tube 21 Measuring tube axis 22 Measuring tube wall 22.1 Normal to measuring tube wall 30 Electronic Measuring / Operating Circuit 100 Procedure for Setting an Ultrasonic Measuring Device 101 First Procedure Step 102 Second Procedure Step 103 Third Procedure Step

Claims

1. Arrangement (2) of ultrasonic transducers of a clamp-on ultrasonic measuring device (1) for measuring a measurement variable of a medium flowing through a measuring tube (20), comprising: At least one pair of ultrasonic transducers (10) arranged on the measuring tube, in particular for mutually transmitting and receiving ultrasonic signals, wherein the ultrasonic transducers in a measuring arrangement (2.2) have an axial arrangement distance (2.22) from each other with respect to a measuring tube axis (21), wherein each ultrasonic transducer comprises a transducer device (11) with a transducer longitudinal axis (11.2) for generating and detecting ultrasonic signals, and a coupling body (12) for transmitting the ultrasonic signals between the transducer device and the measuring tube, wherein the transducer devices are acoustically and mechanically connected to a corresponding coupling body via a transducer-side coupling surface (12.1) of the coupling body, and each transducer device has a side facing the corresponding coupling element with a contact surface area (11.1), wherein the contact surface areas each have a surface area centroid (11.11), wherein a transmitting transducer device is configured to generate an ultrasonic signal field (13), which has a first longitudinal axis (13.1) in the coupling body, in particular parallel to the transducer longitudinal axis, and the ultrasonic signal field in the medium has an opening angle in a longitudinal section plane (22) of the measuring tube through the surface area centroids, wherein the first longitudinal axis defines a reference signal path (2.11) of a reference arrangement (2.1) for the ultrasonic transducers and is part of this reference signal path, and has a longitudinal axis angle to a normal (22.1) of a measuring tube wall (22), wherein the reference signal path defines an axial reference distance (2.12) of the reference arrangement with respect to the surface area centroids of the ultrasonic transducers, wherein a measuring path (2.21) runs between the surface area centroids in the measuring arrangement, and the axial arrangement distance is measured by the surface area centroids, wherein the coupling bodies are acoustically and mechanically connected to the measuring tube via a measuring tube-side coupling surface (12.2), wherein the arrangement distance (2.22) is smaller than the reference distance (2.12), and a target difference between the reference distance and the arrangement distance depends at least on the following feature: Opening angle of the ultrasonic signal field in the medium, wherein an ultrasonic signal causes echo paths in the measuring tube wall (23), which have a common endpoint with the reference signal path, characterized in that a receiving ultrasonic transducer (10) in the measuring arrangement suppresses at least a first echo path on a side of the measuring tube facing the receiving ultrasonic transducer with two reflections in the measuring tube wall, and in particular at least one second echo path with four reflections in the measuring tube wall.

2. Arrangement according to claim 1, wherein the opening angle (13.2) in the medium is defined by an amplitude drop of 20 decibels compared to a maximum amplitude, wherein the reference signal path (2.11) in the medium has a first angle (2.13) to the normal of the measuring tube wall, and the measuring path (2.21) in the medium has a second angle (2.23) to the normal of the measuring tube wall, wherein the magnitude of the second angle is smaller than the first angle, wherein a difference between the first and second angles corresponds to the opening angle multiplied by a factor F, wherein F is at most 1.5, in particular at most 1.2, and preferably at most 1.

3. Arrangement according to one of the preceding claims, wherein the target difference is at least 1 millimeter, in particular at least 2 millimeters, and preferably at least 3 millimeters.

4. Arrangement according to one of the preceding claims, wherein the opening angle (13.2) of the sound beam is smaller than 2 times the first angle.

5. Arrangement according to one of the preceding claims, wherein the transducer device (11) comprises at least one piezo element (11.3).

6. Arrangement according to one of the preceding claims, wherein the opening angle (11.3) in the medium is calculable by the following formula: Ö = arcsin 0.87 ⋅ W / S with W as the wavelength of a central frequency of the ultrasonic signal in the medium and S as the side length of the transducer device in a longitudinal section plane of the measuring tube.

7. Clamp-on ultrasonic measuring device (1) for measuring a measurement variable of a medium in a measuring tube, comprising: An arrangement (2) according to one of the preceding claims, An electronic measuring / operating circuit (30) for operating the ultrasonic transducers and for providing and outputting measurement values of the measurement variable.

8. Method (100) for adjusting an ultrasonic measuring device according to claim 7, wherein in a first method step (101) at least the following parameters are used to determine the reference signal path or reference distance: At least one sound velocity of the coupling body, measuring tube wall, medium, Angle between the first longitudinal axis and a normal to the measuring tube wall, thickness of the measuring tube wall, diameter of the measuring tube, number of ultrasonic signal traverses in the measuring tube, wherein in a second method step (102) at least one of the following parameters is used to determine the target difference: Opening angle in the medium, wherein in a third method step (103) the ultrasonic transducers of a pair are arranged on the measuring tube according to the results of the first and second method steps.

9. Method according to claim 8, wherein the electronic measuring / operating circuit (30) performs the first and second method steps and provides the operator with information for executing the third method step.

10. Method according to claim 9, wherein the operator provides the electronic measuring / operating circuit (30) with information for executing the first method step.