Method for inline control of a tempering process in chocolate production and a measuring arrangement

Abstract

Method for inline control of a tempering process (100) in chocolate production, wherein liquid chocolate (22) flows through a pipeline (12), characterized in that an ultrasonic measuring unit (11) is arranged on the pipeline (12), comprising an ultrasonic transmitter (14) and an ultrasonic receiver (16), and is connected to an evaluation unit (18), wherein the evaluation unit (18) is designed as a microprocessor of the ultrasonic measuring unit (11) and / or as part of a higher-level control unit, wherein the evaluation unit (18) determines an absorption coefficient and a transit time of an ultrasonic signal, wherein the evaluation unit (18) controls a heating device (24) connected to it, wherein a first control variable for the heating device (24) is generated from the absorption coefficient of the ultrasonic signal and a second control variable is generated from the transit time of the ultrasonic signal.

Description

[0001] The invention relates to a method for inline control of a tempering process in chocolate production according to the preamble of independent claim 1. Furthermore, the invention relates to a measuring arrangement for inline control of a tempering process.

[0002] Chocolate products are subject to stringent requirements regarding a wide range of properties, particularly regarding their external appearance, breakability, taste, and / or shelf life. These properties can be significantly influenced by the chocolate's manufacturing process. This is particularly due to the fact that the cocoa butter in chocolate can have a complex crystal structure with different crystal types, with different properties of the chocolate being expressed depending on the composition of the crystal types. To achieve the desired properties of the chocolate, advantageously a beautiful gloss and / or a firm break, a tempering process can be used to adjust the density of a desired crystal type.In particular, the different melting temperatures of the crystal types are exploited to filter out unstable crystal types with low melting temperatures.

[0003] During a preferred tempering process, the chocolate can be fully liquefied and pre-crystallized with a preferred crystal structure during a pre-crystallization step before the chocolate is transferred to a casting mold. In detail, the chocolate can be cooled for pre-crystallization to produce several crystal types with different melting temperatures, whereby a density of preferred crystal types with a higher melting temperature can be increased by reheating above a melting temperature of undesired crystal types. In addition, the pre-crystallized chocolate can be liquefied by reheating such that the chocolate can be conveyed through a pipeline and poured into chocolate molds. Furthermore, the tempering process is preferably adjusted to extend the shelf life of the chocolate as much as possible.Especially for milk chocolate, a maximum temperature should not be exceeded.

[0004] Until now, the tempering process and monitoring of the tempering status have been evaluated by manually taking samples, which are then examined in the laboratory. In particular, samples of hot chocolate are taken from production and analyzed to make adjustments to the tempering process parameters. Such offline processes, which are detached from the actual manufacturing process, are time-consuming and require numerous complex iterations. An offline process results in enormous time losses, and immediate adjustment of the tempering process is not possible.

[0005] Inline methods for monitoring the tempering process are also known, whereby manual sampling can be replaced by an automated sampling device. For example, EP 1 591 786 A1 describes a method and device for recording crystallization-solidification curves of chocolate, with a movable piston for taking a liquid chocolate sample from a pipeline in order to analyze the chocolate sample in a measuring chamber attached to the side of the pipeline. Such devices are also called tempermeters. They are used to determine the degree of tempering of liquid chocolate or a similar fat mass. Such tempermeters are often operated automatically by taking samples of liquid chocolate from a sampling point at adjustable intervals and allowing them to solidify. A temperature sensor measures the temperature profile and transmits it to an evaluation device.The evaluated temperature profile provides information about the degree of tempering or tempering index, and thus about the quality of the pre-crystallized liquid chocolate. Such tempering meters can also be used as part of a control or regulation system.

[0006] Known inline processes have the disadvantage that an intervention device for sampling and / or temperature measurement must be inserted into the flow of chocolate, and a pipeline for transporting the chocolate itself must be extensively redesigned. However, such a redesign can result in the tempering and flow of the chocolate being influenced, which in turn can change the tempering process and the crystal structure. Furthermore, intervention in the pipeline can contaminate chocolate, and cleaning the pipeline can be made even more difficult by the intervention device. It is also conceivable that the intervention device itself could be damaged by a highly viscous flow of chocolate.

[0007] The object of the invention is to propose a method for inline control of a tempering process in chocolate production, which enables reliable and non-invasive control and monitoring of the tempering process while avoiding the problems known from the prior art.

[0008] Furthermore, the task is to specify a measuring arrangement for the inline control of a tempering process.

[0009] The problem is solved with regard to the method by the features of independent claim 1 and with regard to the measuring arrangement by the features of claim 9.

[0010] Advantageous embodiments of the invention are specified in the subclaims.

[0011] According to the invention, a method is claimed for the inline control of a tempering process in chocolate production, wherein liquid chocolate flows through a pipeline. An ultrasonic measuring unit comprising an ultrasonic transmitter, an ultrasonic receiver, and an evaluation unit is arranged on the pipeline, in particular on an outer wall of the pipeline. The evaluation unit determines an absorption coefficient and a propagation time of an ultrasonic signal. The evaluation unit controls a heating device connected to it. A first control variable for the heating device is generated from the absorption coefficient of the ultrasonic signal, and a second control variable is generated from the propagation time of the ultrasonic signal.

[0012] Advantageously, the invention has recognized that two control variables depending on the tempering of the chocolate can be determined by means of the ultrasonic measuring unit without contact and without structural changes to the pipeline.

[0013] In particular, the flow of the chocolate is not affected, and the ultrasonic unit is particularly easy to install and can be installed without opening the pipeline. Another advantage is that continuous and rapid control and / or monitoring is possible without taking individual samples of the chocolate.

[0014] Particularly preferably, a temperature of the chocolate is derived from the measured propagation time of the ultrasonic signal, and a crystal scattering of the chocolate is derived from the measured absorption coefficient in order to continuously control and / or monitor the degree of tempering of the chocolate by means of the heating device. The degree of tempering preferably indicates the quantity or density of crystal nuclei and / or crystal types present within the chocolate.

[0015] Further preferably, in addition to or alternatively to the absorption coefficient of the ultrasonic signal passing through the chocolate in the pipeline, a reflection coefficient of the ultrasonic signal reflected by the chocolate in the pipeline, in particular at the interfaces between chocolate and pipeline walls, can also be determined in order to control the heating device.

[0016] Preferably, the ultrasonic signal is scattered and / or absorbed by cocoa butter crystals within the chocolate. The measured absorption coefficient can be used to evaluate different states of cocoa crystals, each of which scatters the ultrasonic signal differently. Furthermore, by controlling the tempering process using the heating device, a desired pre-crystallization of the liquid chocolate, in particular with a preferred crystal type, can preferably be achieved. In particular, during pre-crystallization, the chocolate can be heated below a melting point of the preferred crystal type in order to melt unstable crystal types with a lower melting point and obtain a favorable liquid and low-viscosity state with preferred pre-crystallization. The pre-crystallization of the cocoa butter in the chocolate is crucial for the quality of the subsequently cooled chocolate.

[0017] Advantageously, the ultrasonic measuring unit can replace a temperature measuring device and enable completely contactless control of chocolate production. In particular, it is not necessary to insert a temperature measuring element into the chocolate flow. Since molten chocolate is a highly viscous medium, it may not be possible to measure the chocolate temperature with a penetration probe. The flow resistance at this probe would be too high. The use of the ultrasonic measuring unit is also advantageous compared to temperature measurement with temperature probes mounted flush with the pipe wall. Temperature probes on the pipe wall are designed to measure the temperature of the molten chocolate in a radially limited outer region of the pipe, whereby the environment of the pipe can influence the temperature measurement.For example, the chocolate near the pipeline may have a different temperature than the one at a radial center of the pipeline. In other words, a temperature sensor itself can be influenced by its installation conditions within the pipeline and, in particular, produce a so-called stamping error. In contrast to the temperature sensors mentioned above, the ultrasonic measuring unit can preferably determine the temperature and / or a temperature change of the chocolate across a pipe cross-section in order to reproduce the tempering state of the chocolate as accurately as possible.

[0018] The absorption coefficient can preferably be determined from the signal amplitude and / or phase position of the ultrasonic signal. The cocoa crystals can scatter the ultrasonic signal and, with increasing absorption coefficient, lead to a decrease in the signal amplitude, particularly with cooling and increasing crystallization.

[0019] Preferably, a change in the crystal state and a change in temperature can be measured using the measured ultrasonic signal, in particular over a process time. Particularly preferably, in the case of over- or under-tempering, the first and second control variables can be adjusted to preferably set a desired tempering, in particular with the desired pre-crystallization, of the chocolate.

[0020] Particularly preferably, high-frequency ultrasound is used to determine the crystal state of the chocolate and, preferably, the amount of cocoa crystals in the chocolate, and to adjust the heating device accordingly. The use of a high-frequency ultrasound signal has the advantage of allowing high sensitivity to changes in the crystal state of the chocolate, particularly to dampening fat crystals in the cocoa butter.

[0021] Ultrasonic waves are also preferably emitted in the form of longitudinal waves and / or shear waves, with the longitudinal waves preferably being used to determine the phase velocity of the liquid chocolate. Using the shear waves, the viscosity of the chocolate can be determined as an additional measurement parameter and used as a further control variable. Pre-crystallization can also be controlled, particularly by measuring the viscosity, with undesired crystal types with a low melting temperature being detected by increasing the viscosity. In addition, a preferred viscosity can be set for flow within the pipeline and pouring into chocolate molds.

[0022] According to a preferred embodiment, sensor data from the ultrasonic measuring unit, in particular in the form of the absorption coefficient and the propagation time of the measurement signal, can be compared with sensor data stored in a database of the evaluation unit or by means of a trained machine learning method in order to determine a degree of tempering, in particular a pre-crystallization of the liquid chocolate, and / or anomalies during the tempering process. In particular, the temperature of the chocolate and / or a viscosity can additionally be evaluated using the ultrasonic signal in order to detect crystal states and / or phase transitions of the crystal structure. In this case, the control variables for the heating device can be adjusted to set a desired crystal structure and / or an error message can be output if a potential anomaly is detected within the sensor data.

[0023] Preferably, a comparison is made with stored sensor data of a reference chocolate product in a liquid reference state in order to determine an ideal tempering degree or tempering state of the chocolate, wherein the heating device is controlled such that the desired tempering degree is achieved during the process.

[0024] The stored sensor data are preferably recorded over a temperature gradient in order to record crystal states in relation to a temperature.

[0025] In particular, the stored sensor data are recorded in the identical pipeline or a pipeline with the same measuring distance between the ultrasonic transmitter and ultrasonic receiver in order to evaluate a reference signal specific to the pipeline.

[0026] Additionally or alternatively, the sensor data can be compared using the trained machine learning method, whereby existing sensor data from the ultrasonic measuring unit are preferably used as training data, for which a chocolate product with the desired degree of tempering could preferably already be produced.

[0027] According to a preferred arrangement of the ultrasonic measuring unit, the ultrasonic transmitter and the ultrasonic receiver are arranged opposite one another on a pipe wall of the pipeline, in particular perpendicular to an axial direction of the pipeline, wherein the ultrasonic signal passes through the chocolate within the pipeline and is scattered by crystal structures of the chocolate.

[0028] In particular, it can be used to measure how ultrasonic waves are affected as they pass through the material. Alternatively or additionally, a pulse-echo ultrasonic reflection method is also conceivable for examining an ultrasonic signal reflected from the chocolate. Preferably, changes in the signal amplitude and / or phase after reflection can be evaluated to determine the condition of the chocolate. However, such a method can have the disadvantage that the chocolate is only examined in an area immediately adjacent to a pipe wall.

[0029] Additionally or alternatively, the ultrasonic transmitter and the ultrasonic receiver can be aligned next to each other along an axial direction of the pipeline and arranged on a pipe wall of the pipeline in order to determine a flow velocity of the chocolate from the transit time of a signal reflected within the pipeline, wherein a third manipulated variable is generated from the flow velocity.

[0030] Preferably, the inner diameter of the pipeline is known to determine the transit time of the ultrasonic signal through the chocolate and additionally evaluate the flow rate of the chocolate. Alternatively or additionally, the ultrasonic signal itself can be used to determine the inner diameter for a pipeline with a known outer diameter.

[0031] In particular, if the temperature and / or crystallization state of the chocolate varies, the flow rate may vary, particularly due to increased flow resistance in the pipeline. The flow rate can be used as an additional measurement to set the desired tempering level. As the chocolate crystallizes, the viscosity and flow resistance may increase, and the flow rate may decrease.

[0032] Preferably, the flow rate can also be evaluated as a function of the electrical power of a chocolate feed pump in order to determine a change in the chocolate's state via a change in flow resistance. In particular, the feed pump's power can be used as an additional third or fourth control variable to control the heating device.

[0033] According to a preferred embodiment, a change in the absorption coefficient and the transit time of the ultrasonic signal, and preferably the flow rate, can be evaluated in combination to detect a chocolate deposit adhering to an inner side of the pipeline, in particular based on an increase in the absorption coefficient at higher flow rates, wherein the flow rate is preferably determined as a function of the transit time. Preferably, the formation of residues can also be used to control the heating device to dissolve the residues. In particular, if an increased absorption coefficient is detected at an increased flow rate, it can be assumed that deposited residues are scattering the ultrasonic signal despite the continued flow of chocolate. The deposits can reduce the cross-section of the pipeline and, at higher absorption coefficients, also increase the flow rate.

[0034] According to a preferred development, a machine learning method is carried out to learn a heating power curve of the tempering process of the heating device for chocolate production, comprising the following steps in a preferred order. According to a preferred first step, a condition monitoring of a crystal state or degree of tempering is carried out as a state variable during the tempering process, wherein the crystal state is estimated based on the first and second manipulated variables. According to a preferred second step, a crystal state of a finished chocolate product is recorded as determination data. According to a preferred third step, the heating power curve is learned based on an output of the condition monitoring and the determined determination data. Preferably, further of the aforementioned sensor data can be used to adjust the heating power curve, in particular a flow rate.In particular, a modified control program is output by a machine learning unit, preferably a neural network.

[0035] In this context, it may be preferred that measured ultrasonic signals are characterized as accurately as possible with a predetermined cost function to a desired crystal state by means of the machine learning method in order to map the heating power curve to predetermined desired values.

[0036] According to a preferred embodiment, it is conceivable that the above-mentioned measured variables, which can be evaluated from the ultrasonic signal, are combined in order to map a measured variable representative of the degree of tempering and to generate a common control variable for the heating device.

[0037] The invention further relates to a measuring arrangement for the inline control of a tempering process in chocolate production, in particular for carrying out a previously described method for monitoring and / or controlling a chocolate flow through a pipeline. The measuring arrangement has an ultrasonic measuring unit which is arranged on a pipe wall of the pipeline, wherein the ultrasonic measuring unit comprises an ultrasonic transmitter, an ultrasonic receiver and an evaluation unit, wherein the evaluation unit can be connected or is connected to a heating device for controlling the tempering process and wherein the evaluation unit is designed to determine an absorption coefficient of the ultrasonic signal as a first manipulated variable and a propagation time of the ultrasonic signal as a second manipulated variable for controlling the heating device.

[0038] In particular, liquid chocolate flows through the pipe during the tempering process.

[0039] The ultrasonic measuring unit preferably has a local heating and / or cooling device to regulate the temperature of the pipeline in a mounting area of ​​the ultrasonic measuring unit. In particular, this ensures a homogeneous temperature distribution and a homogeneous melting state of the chocolate. Advantageously, both passive and active temperature influences caused by the ultrasonic measuring unit can be compensated.

[0040] The evaluation unit can preferably be designed as a microprocessor of the ultrasonic measuring unit and / or as part of a higher-level control unit.

[0041] The invention is explained in more detail below using exemplary embodiments with reference to the drawings.

[0042] They show schematically: Fig. 1: Side view of a measuring arrangement with ultrasonic measuring unit, Fig. 2: Side view of another embodiment of a measuring arrangement with ultrasonic measuring unit, Fig. 3: Tempering process for chocolate production.

[0043] In the following description of the preferred embodiments, like reference numerals designate like or comparable components.

[0044] The Fig. 1 shows a measuring arrangement 10 for carrying out and monitoring a tempering process for chocolate production, with an ultrasonic measuring unit 11 which is arranged on a pipeline 12 and sends an ultrasonic signal 20 through a liquid chocolate 22 flowing within the pipeline 12.

[0045] According to a preferred embodiment, an ultrasonic transmitter 14 and an ultrasonic receiver 16 are arranged opposite one another, in particular perpendicular to an axial direction AX of the pipeline 12, on a pipe wall 26 in order to generate an ultrasonic signal 20 penetrating the chocolate 22. The ultrasonic signal 20 can be scattered within the chocolate 22 by cocoa crystals (not shown). Such scattering is illustrated by the deflected and scattered ultrasonic components 30, wherein in particular these ultrasonic components 30 do not reach the ultrasonic receiver 16 and the received signal amplitude or signal strength can be reduced. In other words, depending on the scattering, an absorption coefficient of the chocolate 22 can preferably be determined, which is representative of a crystal state of the chocolate 22.In particular, a tempering level of the tempering process representative of the number of crystallization nuclei within the chocolate 22 can be determined by means of the ultrasonic measuring unit 11. The ultrasonic measuring unit 11 can preferably be used to monitor and / or control a desired pre-crystallization of the chocolate 22.

[0046] In addition to measuring the absorption coefficient, the transit time of the ultrasonic signal 20 can be used to determine a temperature and / or a temperature change of the chocolate 22. Preferably, the transit time can be evaluated in conjunction with known geometric values ​​for the pipeline 12, in particular an outer diameter D and an inner diameter d, preferably in conjunction with material parameters for the pipeline 12 and the chocolate 22, in order to determine the temperature of the chocolate 22. Alternatively or additionally, a proportional temperature change can be evaluated directly from a transit time change in order to monitor and / or control the tempering process for chocolate production.

[0047] Sensor data from the ultrasonic measuring unit 11, in particular the absorption coefficient and the transit time, are determined by an evaluation unit 18, which can be connected to a heating device 24 of the pipeline 12 to control the tempering process. The absorption coefficient and the transit time are preferably used as the first and second control variables for controlling the heating device 24.

[0048] The ultrasonic measuring unit 11 has the advantage that no temperature measuring element or sampling device has to intervene in the pipeline 12 itself to control and / or monitor the tempering process.

[0049] The Fig. 2 shows an alternative or additional embodiment of a measuring arrangement 10, wherein the ultrasonic transmitter 14 and the ultrasonic receiver 16 are preferably arranged next to one another in a common housing 32 and along the axial direction AX on the pipe wall 26 of the pipe 12. The ultrasonic signal 20 is preferably coupled into the pipe 12 at an angle, and the ultrasonic signal 20 reflected on the inner side 28 of the pipe 12 is measured. A flow velocity and a flow rate of the chocolate 22 can be determined from the measured propagation time of the ultrasonic signal 20, preferably a wall thickness s, and preferably a distance a between the ultrasonic transmitter 14 and the ultrasonic receiver 16. Preferably, a flow rate can be evaluated by means of the evaluation unit 18 and used to control the heating device 24.

[0050] An exemplary tempering process 100 during chocolate production and a temperature curve T over a time course t can be Fig.3. Preferably, a chocolate is heated at room temperature RT by means of the heating device 24 to a first process state ST1, wherein the chocolate 22 is preferably completely melted. Subsequently, the chocolate 22 is cooled to a second process state ST2 until a phase transformation takes place and a first preferred crystal type forms, wherein unstable and less advantageous second crystal types can additionally form within the chocolate 22. Further subsequently, the temperature T is increased to a third process state ST3 below a melting temperature of the first crystal type in order to remove the second crystal types by melting. In particular, the increased temperature T in the third process state ST3 can additionally be used to set a desired viscosity in order to preferably produce a chocolate that flows well.

[0051] In particular, by measuring the absorption coefficient using the ultrasonic measuring unit 11, it can be determined whether the desired crystal state and a desired pre-crystallization have been achieved and / or are unchanged. Furthermore, by measuring the time of flight, a temperature T can be set during the annealing process 100 by controlling the heating device 24. List of reference symbols 10 Measuring arrangement 11 Ultrasonic measuring unit 12 Pipeline 14 ultrasonic transmitters 16 ultrasound receivers 18 Evaluation unit 20 Ultrasonic signal 22 chocolate 24 Heating device 26 Pipe wall 28 Inside of the pipeline 30 Scattering of the ultrasonic signal 32 housings 100 tempering process AX axial direction a Distance between ultrasonic transmitter and ultrasonic receiver D Outer diameter of the pipeline d inner diameter of the pipeline T Temperature t time RT room temperature ST1,2,3 first, second and third process state QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 1 591 786 A1

[0005]

Claims

[1] Method for inline control of a tempering process (100) in chocolate production, wherein liquid chocolate (22) flows through a pipeline (12), characterized by that an ultrasonic measuring unit (11) is arranged on the pipeline (12), which comprises an ultrasonic transmitter (14), an ultrasonic receiver (16) and an evaluation unit (18), wherein the evaluation unit (18) determines an absorption level and a propagation time of an ultrasonic signal, wherein the evaluation unit (18) controls a heating device (24) connected to it, wherein a first manipulated variable for the heating device (24) is generated from the absorption level of the ultrasonic signal and a second manipulated variable is generated from the propagation time of the ultrasonic signal. [2] Method according to claim 1, characterized bythat a temperature (T) of the chocolate (22) is derived from the measured propagation time of the ultrasonic signal and a crystal scattering of the chocolate (22) is derived from the measured absorption level in order to control and / or monitor a tempering level of the chocolate (22), in particular a pre-crystallization of the liquid chocolate (22), by means of the heating device (24). [3] Method according to claim 1 or 2, characterized bythat sensor data of the ultrasonic measuring unit (11), in particular in the form of the degree of absorption and the propagation time of the ultrasonic signal, are compared with sensor data stored in a database or by means of a trained machine learning method in order to determine a degree of tempering, in particular a pre-crystallization of the liquid chocolate (22), and / or anomalies during the tempering process (100), wherein the control variables for the heating device (24) are adapted to set a desired crystal structure and / or an error message is output if a potential anomaly is detected within the sensor data. [4] Method according to one of claims 1 to 3, characterized bythat the ultrasonic transmitter (14) and the ultrasonic receiver (16) are arranged opposite one another on a pipe wall (26) of the pipe (12), in particular perpendicular to an axial direction (AX) of the pipe (12), wherein the ultrasonic signal passes through the chocolate (22) within the pipe (12) and is scattered by crystal structures of the chocolate (22). [5] Method according to one of claims 1 to 4, characterized by in that the ultrasonic transmitter (14) and the ultrasonic receiver (16) are aligned next to one another along an axial direction (AX) of the pipeline (12) and are arranged on a pipe wall (26) of the pipeline (12) in order to determine a flow rate of the chocolate (22) from the propagation time of a signal reflected within the pipeline (12), a third manipulated variable being generated from the flow rate. [6] Method according to one of claims 1 to 5, characterized bythat an electrical power of a feed pump of the chocolate (22) is evaluated in order to determine a change in the state of the chocolate (22) via a changed flow resistance, wherein an additional control variable is generated from the electrical power. [7] Method according to claim 5 or 6, characterized by that a change in the degree of absorption and the propagation time of the ultrasonic signal as well as the flow velocity are evaluated in combination in order to detect a chocolate deposit adhering to an inner side (28) of the pipeline (12), in particular based on an increase in the degree of absorption at a higher flow velocity. [8] Method according to one of claims 1 to 7, characterized by that a machine learning process is carried out to learn a heating power curve of the tempering process (100) of the heating device (24), comprising the following steps: - performing a state monitoring of a crystal state as a state variable during the annealing process (100), wherein the crystal state is estimated based on the first and second manipulated variables, - Recording the crystal state of a finished chocolate product as determination data, - Learning the heating output curve based on a condition monitoring output and the determined determination data. [9] Measuring arrangement for inline control of a tempering process (100) in chocolate production, in particular for carrying out a method according to one of claims 1 to 8, in order to monitor and / or control a chocolate flow through a pipeline (12), characterized byin that the measuring arrangement (10) has an ultrasonic measuring unit (11) which is arranged on a pipe wall of the pipeline (12), wherein the ultrasonic measuring unit (11) comprises an ultrasonic transmitter (14), an ultrasonic receiver (16) and an evaluation unit (18), wherein the evaluation unit (18) can be connected or is connected to a heating device (24) for controlling the tempering process (100) and wherein the evaluation unit (18) is designed to determine an absorption coefficient of the ultrasonic signal as a first manipulated variable and a propagation time of the ultrasonic signal as a second manipulated variable for controlling the heating device (24). [10] Measuring arrangement according to claim 9, characterized by that the ultrasonic measuring unit (11) has a local heating and / or cooling device in order to temper the pipeline (12) in a mounting area of ​​the ultrasonic measuring unit (11).

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