Patent Application
20240288292
The invention relates to an arrangement of ultrasonic transducers, a clamp-on ultrasonic measuring device for measuring a measured variable of a medium located in a measurement tube having such an arrangement, and to a method for adjusting the ultrasonic measuring device.
Ultrasonic transducers of clamp-on ultrasonic measuring devices are used to transmit and receive ultrasonic signals to be able to draw conclusions about a property of a medium in a measurement tube, for example, from a signal propagation time of the ultrasonic signals or a propagation time difference between two ultrasonic signals propagating in opposite directions; see for example DE10254053A1.
A problem with typical clamp-on ultrasonic measuring devices is that ultrasonic signals cause signal reflections at different interfaces, which reflections also arrive at a receiving ultrasonic transducer and overlap the actual measuring signal.
The object of the invention is therefore to minimize the influence of such interfering signal reflections.
The object is achieved by an arrangement according to independent claim 1, by a clamp-on ultrasonic measuring device according to independent claim 8, and by a method according to independent claim 9.
An arrangement according to the invention of ultrasonic transducers of a clamp-on ultrasonic measuring device for measuring a measurand of a medium flowing through a measurement tube, wherein the ultrasonic transducers are arranged on the measurement tube, comprises:
The opening angle can, for example, be calculated or specified by a formula in which, for example, a wavelength of the ultrasonic signal in the medium and a side length of the transducer element are used. The person skilled in the art can also use other or further measurands for this purpose.
However, the opening angle can also be determined by calibration measurements, for example.
It has been shown that a measurement arrangement having an arrangement distance less than the reference distance reduces interfering influences, for example, due to signal reflections, and thus simplifies signal evaluation.
A contact surface region can, for example, simply be a contact surface, such as in a one-piece piezoelectric element. The contact surface can, for example, be shaped like a circle or a regular polygon, for example, but is not limited thereto. However, the contact surface region can also be spanned by several non-contiguous contact surfaces. The surface region centroid can also lie outside of a contact surface.
The transducer apparatus can, for example, be disk-shaped. However, it can also be block-shaped, for example. The transducer apparatus can be a single piece or composed of several components.
In one embodiment, the opening angle in the medium is defined by an amplitude drop of 20 decibels relative to a maximum amplitude,
It has been shown that in this way a receiving ultrasonic transducer receives a sufficiently good ultrasonic signal in an edge region of the ultrasonic signal field and benefits from a minimization of interference.
In one embodiment, the target difference is at least 1 millimeter and in particular at least 2 millimeters and preferably at least 3 millimeters. In this way, it is ensured that the invention has a minimum effect.
In one embodiment, the opening angle of the ultrasonic signal field is less than 2 times the first angle.
In one embodiment, an ultrasonic signal causes echo paths in the measurement tube wall which have a common end point with the reference signal path,
In this way, substantial interference is suppressed and measurement properties of the measurement arrangement are improved. Suppressing an echo path does not preclude edge regions of echo signals from being picked up by a receiving ultrasonic transducer.
The term “echo path” refers to a central region, with maximum echo amplitude, of an echo signal.
In one embodiment, the transducer apparatus has at least one piezoelectric element.
In one embodiment, the opening angle in the medium is calculable by the following formula:
A clamp-on ultrasound measuring device according to the invention for measuring a measurand of a medium located in a measurement tube comprises:
In a method according to the invention for adjusting an ultrasonic measuring device according to the invention,
In one embodiment, the electronic measuring/operating circuit performs the first method step and the second method step and provides information to an operator in order to perform the third method step.
In one embodiment, the operator provides information to the electronic measuring/operating circuit in order to perform the first method step.
The invention will now be described with reference to exemplary embodiments.
A contact surface region can, for example, simply be a contact surface, such as in a one-piece piezoelectric element. The contact surface can, for example, be shaped like a circle or a regular polygon, for example, but is not limited thereto. However, the contact surface region can also be spanned by several non-contiguous contact surfaces. The surface region centroid can also lie outside of a contact surface.
The transducer apparatus can also be block-shaped, for example. The transducer apparatus can be a single piece or composed of several components.
A first arrangement corresponds to a reference arrangement 2.1, and a second arrangement corresponds to a measurement arrangement 2.2 according to the invention. In this case, 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. Typically, the first longitudinal axis 13.1 runs along a transducer longitudinal axis 11.2 starting from the surface region centroid 11.11, as illustrated.
In this case, the reference arrangement has an axial reference distance 2.12, which is dimensioned parallel to a measurement tube axis 21 between the surface region centroids 11.11 of the contact surfaces of the transducer apparatuses of the ultrasonic transducers. Accordingly, a measurement arrangement has an axial arrangement distance 2.22.
A problem with the reference arrangement is, for example, that not only the ultrasound signal itself but also reflections of the ultrasound signal reach a receiving ultrasonic transducer at different interfaces via echo paths and thus overlap the ultrasound signal in an interfering manner. Echo paths are illustrated by way of example by the dashed lines, in which two reflections occur at measurement tube interfaces in a measurement tube wall 22 of the measurement tube. There are also further echo paths with more than two reflections.
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 the reference distance and arrangement distance is dependent on at least the following feature:
In this way, the influence of interference such as reflected ultrasonic signals can be reduced via echo paths. The relevance of echo paths with respect to their interference character increases as the opening angle of the ultrasonic signal field increases. The opening angle of the ultrasonic signal field in the medium is a simple variable because the ultrasonic signal field is substantially defined by a far-field character in the medium. As a measure for the opening angle, for example, a formula can be used in which, for example, a wavelength of the ultrasonic signal in the medium and a side length of the transducer element are used. The person skilled in the art can also use other or further measurands for this purpose. However, the opening angle can also be determined by calibration measurements, for example.
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 to the normal of the measurement tube wall, wherein the measurement path 2.21 in the medium has a second angle 2.23 to the normal of the measurement tube wall, wherein a magnitude of the second angle is smaller than the first angle, wherein an angle difference between the first angle and the second angle 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. It has been shown that in this way a receiving ultrasonic transducer receives a sufficiently strong ultrasonic signal in an edge region of the ultrasonic signal field and benefits from a minimization of interference.
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 that the effect according to the invention has a minimum effect.
In one embodiment, as illustrated in
The transducer apparatus 11 can have, for example, at least one piezoelectric element 11.3.
The opening angle 11.3 in the medium can be calculated or measured by the following formula: opening angle=arcsin(0.87*W/S), where W is the wavelength of a central frequency of the ultrasonic signal in the medium and S is the side length of the transducer apparatus in a longitudinal sectional plane of the measurement tube, and said opening angle is defined by an amplitude drop of 20 decibels relative to a maximum amplitude.
In case of a reference arrangement as well as a measurement arrangement having more than one ultrasonic signal traverse in the measurement tube, the above applies, wherein the target difference is multiplied by a factor corresponding to a number of traverses.
In a first method step 101 at least the following variables are used to determine the reference signal path or reference distance:
The course of the reference signal path can thus be determined using Snell's law of refraction.
In a second method step 102, at least the opening angle in the medium is used to determine the reference difference,
In one embodiment of the method, the electronic measuring/operating circuit 30 performs the first method step and the second method step and provides information to an operator in order to perform the third method step.
In one embodiment of the method, the operator provides the electronic measuring/operating circuit 30 with information required to perform the first method step. The information in this case is, for example, a typical sound velocity of the medium.
In this way, the measurement arrangement according to the invention can be configured in a simple and reliable manner.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 115 546.0 | Jun 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/063476 | 5/18/2022 | WO |
