System for testing propagation-time-measuring apparatuses

Abstract

The invention relates to a system for testing a propagation-time-measuring apparatus (1), the system comprising: a fluid circuit (2) comprising a pressure vessel (3) which has at least one movable planar element, and comprising a pump (4), the pressure vessel (3) and the pump (4) being designed to interact in such a way that changes over time in the length of a section (5) between one portion of the planar element (9) and another portion of the pressure vessel (10), across which section (5) the propagation time is to be measured, are brought about. The invention also relates to corresponding methods and uses of the system.

Description

[0001] System for testing time-of-flight measuring equipment

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a system for testing time-of-flight measuring apparatus, a method for testing time-of-flight measuring apparatus using this system, and a use of such a system for testing time-of-flight measuring apparatus.

[0004] BACKGROUND

[0005] The measurement of signal propagation times using time-of-flight measuring devices is well known. These devices are often used to examine the properties of objects or systems. Relevant examples include medical care and diagnostics, quality inspections in industrial processing, the development of autonomous vehicles, and many other applications. What many of these application areas have in common is that the measurements made by such time-of-flight measuring devices must be reliable, as otherwise injury to life or limb or economic damage could occur. To avoid such cases, it is necessary to be able to test time-of-flight measuring devices to ensure that they function properly and as expected. Various systems are known in the state of the art for testing time-of-flight measuring devices. However, only static systems and quasi-static systems are known.Static systems are temporally unchanging and therefore only allow static measurements of transit times and thus only static testing of transit time measuring devices. Typical examples are immutable systems used for training purposes in medical training or sample workpieces in industry. Quasi-static systems are externally static systems that can undergo temporal internal changes through the introduction of another substance or additional components, but which do not serve to change the transit time. Examples of this can be found in arterial models in medical imaging diagnostics, which are intended to simulate blood flow, for example, through the introduction of fluid.

[0006] SUMMARY

[0007] A key parameter in time-of-flight measurement, which has a correspondingly relevant influence on the measurements of time-of-flight measuring devices, is the length of the track over which the time-of-flight is measured. The inventors recognized that for more comprehensive and accurate testing of a time-of-flight device under realistic conditions, a static track does not meet the requirements of many applications because these applications are subject to a time-varying track length, and in some cases, the temporal change in the time-of-flight is relevant for evaluations. However, the prior art does not disclose any systems suitable for testing time-of-flight measuring devices based on temporal changes in the travel distance.

[0008] It is therefore the object of the present disclosure to provide a system which enables the testing of time-of-flight measuring devices more comprehensively.

[0009] This object is achieved by a system for testing time-of-flight measuring devices according to claim 1. Claim 15 relates to a method for testing time-of-flight measuring devices using the system according to the invention. Claim 24 describes the use of the system according to the invention for testing time-of-flight measuring devices. Claims 2 to 14 relate to particularly advantageous embodiments of the system according to the invention. Claims 16 to 23 describe further refinements of the method according to the invention.

[0010] This object is achieved because the system according to the invention is suitable for testing a transit time measuring apparatus and the system comprises: a fluid circuit, this comprising: a pressure vessel (e.g. a pressure vessel with a variable volume), which comprises at least one movable surface element (e.g. a wall of the pressure vessel, e.g. a ceiling, a floor, an (outer) side wall of the pressure vessel or a wall present in the interior of the pressure vessel between the side walls) and a pump, wherein the pressure vessel and the pump are designed to interact in such a way that time-dependent changes in the length of a path between a section of the surface element and another section of the pressure vessel (e.g. a wall of the pressure vessel, e.g. a ceiling, a floor, an (outer) side wall of the pressure vessel or a wall present in the interior of the pressure vessel between the side walls), over which path the transit time is to be measured, are brought about.

[0011] Because the pressure vessel and the pump are designed to interact in such a way that time-dependent changes in the length of a path over which the transit time is to be measured are brought about, a temporal variation in the length of the path can be realized, which enables more comprehensive testing of a transit time measuring apparatus. Because the temporal variation is realized according to the invention by means of a fluid circuit, a test system is provided with which the path variation can be realized reliably, effectively and cost-effectively. The pump can preferably pump the fluid in the fluid circuit in such a way that part of the fluid located in the pressure vessel is displaced from it. Another part of the fluid flows in. The pressure vessel is designed in such a way that it comprises a movable surface element and is subject to volume changes during this time, such that the movable surface element moves.Due to the movement of the movable surface element, the length of a path between one section of the surface element and another section of the pressure vessel also changes, allowing a transit time measuring device to be tested using the changing length of the path. In particular, with a suitable pump selection, repeated changes in the length of a path between one section of the surface element and another section of the pressure vessel can occur. This makes it possible to test a transit time measuring device over more than one change.

[0012] In a preferred aspect of the invention, the fluid circuit of the system according to the invention comprises one or more controllable valves, which, in conjunction with the pressure vessel and the pump, are designed to interact in such a way that (said) time-dependent changes in a length between one section of the surface element and another section of the pressure vessel, over which distance the running time is to be measured, are brought about. The use of such a combination of valves, pump, and pressure vessel offers the advantage that changes in the distance and the pressure prevailing in the pressure vessel can be configured in different ways. For example, scenarios with different distance changes between one section of the movable surface element and another section of the pressure vessel can be brought about. In this case, it is not necessary to modify or replace the pressure vessel or the pump.This allows for virtually any degree of complexity in the amplitude of the change in the distance over which a time-of-flight measurement is to be achieved without complicated modifications to the components themselves. The system can thus be adapted to many situations in which time-of-flight measurements are performed, thus allowing the testing of time-of-flight measurement devices in various technical fields.

[0013] In a preferred aspect of the invention, at least one of the one or more controllable valves is designed to be opened and closed again at a predetermined frequency. Due to the periodic opening and reclosing of a valve, the volume and thus the length of a path between one section of the surface element and another section of the pressure vessel, over which path the transit time is to be measured, changes with the same period. These periodic changes are correspondingly reflected in the transit time of a signal. Such a system configuration therefore allows the testing of a transit time measuring apparatus over several periods of such a change in the length of the path over which the transit time is to be measured.This makes it possible, for example, to achieve more accurate test results than with measurements over a single period, as measured transit times can be averaged over periods, thereby smoothing out significant measurement errors. In particular, the consistency of measurements from a transit time measuring device can also be tested, allowing temporal changes in the measurements to be detected that go beyond the periodicity of changes in the length of the path over which the transit time is measured. In addition, the opening and closing of the valve at a predetermined frequency enables the determination of one or more path characteristics, such as an oscillation center or values ​​corresponding to certain percentages of the maximum change amplitude, due to the resulting periodic changes in the distance between one section of the surface element and another section of the pressure vessel.Corresponding transit time parameters can also be determined for the transit time measurement. Comparing the times at which the length of the path between one section of the surface element and another section of the pressure vessel exceeds and / or falls below the transit time parameters with the corresponding times at which the transit time exceeds and / or falls below the corresponding transit time parameters allows for sensitive testing of the sensitivity and time resolution of a transit time measurement device. In particular, the opening and closing of the valve at a predetermined frequency, due to the resulting periodic changes in the distance between one section of the surface element and another section of the pressure vessel, allows the determination of statistical parameters of the properties of the temporal change of the path and in the temporal recording of the transit time measurement.These statistical parameters can include, for example, mean values, variations, or other known statistical parameters; the properties of the temporal change can include, for example, the period, the amplitude, or other properties of periodic functions. By determining statistical parameters over several periods, testing of a transit time measuring device can be made robust against measurement errors. Furthermore, the opening and closing of a valve at a predetermined frequency enables the testing of the transit time measuring device under changing conditions within the fluid. For example, turbulence can occur within the fluid, which can cause the transit time of a signal to be disturbed. Furthermore, some of the systems to be measured by transit time measuring devices, particularly biological systems, are subject to periodic changes.Intracranial pressure and the associated intracranial compliance also exhibit pulsatility, which depends, among other things, on the human heartbeat. Due to the human heart rhythm, periodic changes in pressure within the skull occur, so that the skullcaps are subject to small pressure-induced movements that only compensate for the increasing pressure to a very limited extent. However, this skullcap movement causes a change in the distance between two sections of the skull, which leads to changes in the travel time when a sound signal travels through the skull. At higher mean pressure, the skullcap distance changes statically; this is not recorded in the travel time measurement itself, but the changed dynamic pressure transmission and the parallel increased pulsatility both contribute significantly to the pressure-dependent changes in the dynamic travel time measurements with increasing intracranial pressure.

[0014] Since the measurement of intracranial pressure or intracranial compliance using transit-time measurement devices represents a non-invasive alternative to invasive methods, which are associated with high risks of infection and surgery, testing such transit-time measurement devices is particularly relevant. The system according to the invention is also suitable for testing transit-time measurement devices used on humans.

[0015] Many of the products and biological systems that are examined using time-of-flight measuring equipment contain components that are also subject to changes in the length of the path over which the travel time of a signal is measured. Corresponding components are often also equipped with fluid circuits. In such cases, the changes in the length of the path usually depend on pressure-dependent changes. In a particularly preferred aspect of the invention, at least one of the one or more controllable valves is therefore designed to open and close automatically depending on a pressure in the fluid present at the at least one valve. The human heart valves, for example, open and close depending on the pressure in the blood. In order to carry out the already mentioned tests of time-of-flight measuring equipment, which is used to determine the intracranial pressure orIn order to optimize the intracranial compliance or pathological changes of those used, a realistic reproduction of the conditions of the human body is therefore advantageous.

[0016] Furthermore, it can be advantageous to minimize the impact of external systems on a system used to test measurement equipment, thus avoiding as many external sources of interference as possible. This is especially true for delicate measurements such as time-of-flight measurements, where even small disturbances can lead to significant distortions in the test results.

[0017] In a particularly preferred aspect of the invention, the fluid circuit of the system according to the invention comprises a first controllable valve and a second controllable valve. Configuring the system with two valves increases the flexibility of the system and the possibilities of inducing various scenarios in the changes in the length of the path over which the transit time is measured. This allows for more complex testing of transit time measuring devices. For example, by connecting the first and second valves in parallel, it is possible to better regulate the flow rate of the fluid from the pressure vessel into the circuit, so that the dynamics of the changes in the length of the path can be adapted to better test the transit time measuring device. This is ensured in particular by the fact that the dynamics of the changes in the length of the path are ideally reflected in the transit time curves recorded by the transit time measuring device.The dynamics of such changes therefore allow a more precise testing of the time-of-flight measuring equipment than flatter areas of the curves.

[0018] In a further aspect of the invention, the first controllable valve and the second controllable valve can be controlled independently of one another. This allows, for example, the opening and closing of the first valve at a predetermined frequency, while the second valve can be opened and closed independently. This allows time-of-flight measuring devices to be tested on systems with periodic changes and non-periodic disturbances. When testing a time-of-flight measuring device, it is therefore possible to ensure that disturbances in the system being measured using the time-of-flight measuring device are also reflected in the time-of-flight measurements, or that problems in the measurement of such disturbances can be detected using the tested time-of-flight measuring device.Furthermore, by independently opening and closing the first and second controllable valves, changes in both the acceleration and the speed of the changes in the length of the path over which the transit time is to be measured can be induced. Since these changes should also be reflected in the transit time measurements, they can be examined for their existence. If they exist, the dynamics of the changes in the length of the path and in the changes in the transit time can be analyzed and compared. This therefore enables better and more complex testing of transit time measuring devices.In a preferred aspect of the invention, the first controllable valve is designed to open and close again at a first frequency, and the second controllable valve is designed to open and close again at a second frequency different from the first frequency. This allows for superpositions of periodic changes in the volume of the pressure vessel and thus in the length of the path over which the transit time is to be measured. This increases the complexity of the possible changes and is particularly suitable for simulating frequently occurring changes in the length of the path. For example, as already described, it is possible to draw conclusions about intracranial pressure and intracranial compliance using transit time measurements of a sound signal through the human skull.Intracranial pressure and intracranial compliance are subject to periodic changes due to the human heart rhythm. In pathological changes in the heart rhythm, such as arrhythmias, another rhythm with a different frequency is superimposed on the normal heart rhythm. Therefore, it is advantageous to be able to artificially recreate such realistic scenarios for testing transit time measurement devices for later operation.

[0019] In a further preferred aspect of the invention, the first controllable valve is designed to open and close automatically depending on the pressure in the fluid at the first controllable valve, and the second controllable valve is designed to open and close automatically depending on the pressure in the fluid at the second controllable valve. The first controllable valve can open and close depending on a constant value of the applied pressure, while the second controllable valve opens and closes depending on different values ​​of the applied pressure. For example, with appropriate interaction of valves, pressure vessel, and pump, it is possible to change the dynamics of the changes in the length of the path between one section of the surface element and another section of the pressure vessel, over which the running time is measured, in such a way that, for example,be made flatter or steeper. Corresponding changes should also be reflected in the signals from the measurements of a time-of-flight measuring device during a test. This allows the sensitivity of a time-of-flight measuring device to be tested more effectively than before.

[0020] Due to the sensitive nature of transit time measurements with transit time measurement devices, mechanical disturbances in the system being measured should be avoided as much as possible during testing of a transit time measurement device, as these can have significant effects on the measurement result and thus the test outcome. To minimize external mechanical influences on the system, the controllable valves are controlled via electronic or electromagnetic signals in a preferred aspect of the invention.

[0021] Testing measurement equipment is particularly relevant in those areas of a measurement signal where strong dynamics are present. For example, parts of a signal with a steep gradient are ideal for testing, as both the start and end points of a rising part of the signal can be located with great accuracy. Furthermore, the absolute gradient of a signal can be examined relative to the signal's mean value. These and other investigations into changes in the length of the path over which the propagation time is measured should also be possible on the propagation time of a signal over this path, in order to test the corresponding propagation time measuring equipment based on the correlation between the two signals.In a further preferred aspect of the invention, the one or more controllable valves are designed to open at different opening speeds and close at different closing speeds. Thus, the acceleration of the change in the distance between one section of the surface element and another section of the pressure vessel can be varied. The curvature of the temporal measurement signal of a time-of-flight measurement device is also changed, allowing further testing of the device.

[0022] In another particularly preferred aspect of the invention, the one or more controllable valves are designed to allow different degrees of opening. This results in the volume flow from the pressure vessel being adjustable. Thus, the rate of change in the length of the path between one section of the surface element and another section of the pressure vessel can be varied. The gradient of the temporal measurement signal of a time-of-flight measuring device is thus also changed, allowing further testing of the device.In addition, by changing the degree of opening of the valves in a time-graded manner, the acceleration of the change in the length of the path between one section of the surface element and another section of the pressure vessel can be changed in a discrete manner, so that the curvature of the temporal measurement signal of a time-of-flight measuring device also contains discrete changes, thus enabling an even more detailed inspection of the device.

[0023] In many typical applications of time-of-flight measurements, measurements are preferably carried out over an extended period of time. Especially in the case of medical measurements, such as non-invasive measurements of intracranial pressure or correlated variables such as intracranial compliance, it is often a matter of recording these over a specific observation period in order to enable diagnoses and monitoring of the patient's condition. In a particularly preferred aspect of the invention, the system therefore comprises an external control unit designed to control the one or more controllable valves. This simplifies the control of the entire system through centralized control. Furthermore, tests of time-of-flight measuring devices can thus be carried out in continuous operation, especially over long periods of time. This is particularly advantageous for testing the stability of the measurements from time-of-flight measuring devices.

[0024] In a preferred aspect of the invention, the pressure vessel comprises at least one wall, wherein the movable surface element of the pressure vessel comprises at least one wall of the pressure vessel. In particular, the pressure vessel can comprise more than one wall, wherein the movable surface element encloses one or more of the walls. For example, the pressure vessel can consist of two interconnected and aligned cups, the edges of which are connected such that the pressure vessel is sealed. The movable surface elements then relate to the upper wall and parts of the side walls or side wall of the pressure vessel. In a further particularly preferred aspect of the invention, the system comprises a pressure vessel made of elastic material. A particular advantage of such a pressure vessel is that it can expand isotropically or nearly isotropically.In such a case, every part of the pressure vessel's surface is a movable surface element. Thus, the length of the path over which a transit time is to be measured to test a transit time measuring device can be varied at different sections of the pressure vessel. This can facilitate handling. This is very advantageous given the large number of different users from different technology areas with different technical backgrounds.

[0025] Other designs of the pressure vessel are also conceivable, some of which are described below.

[0026] The invention further achieves this object because the inventive method for testing a propagation time measuring apparatus with the inventive system comprises the following: sending a signal over the path, receiving the signal after passing through the path, and determining the propagation time of the signal over the path, characterized by time-dependent variation of the length of the path by means of the interaction of the pressure vessel and the pump. By varying the length of the path over which the propagation time is to be measured over time, different propagation times of the signal to be transmitted can be achieved between transmission and reception. This allows the propagation time measuring apparatus, with the aid of which the signal is transmitted and received, to be better tested because its use in various situations can be simulated.In addition, it is possible to simulate dynamics in systems to be measured for which runtime equipment can only be inadequately tested by static testing.

[0027] In a preferred aspect of the method according to the invention, the signal is transmitted through a medium and the physical state of this medium is changed. The medium can be a fluid, as in the system according to the invention. The change in the physical state of the medium can consist of changing the pressure prevailing in the medium. The change in the pressure in the fluid of the fluid circuit in the system according to the invention results in the fluid being able to expand the pressure vessel by moving a movable surface element of the pressure vessel and thus changing the length of the path between one section of the movable surface element and another section of the pressure vessel.

[0028] In a further preferred aspect of the invention, the method comprises setting the frequency of the temporal changes in the length of the route, determining the frequency of the temporal changes in the transit time, and comparing the set and determined frequencies to test the transit time measuring device. The frequency of the changes in the length of the route can be set using a valve designed for this purpose, which can open and close again at this predetermined frequency. The same frequency can then be found in the dynamics of the changes in the transit time, provided the transit time measuring device is operating properly. It is therefore possible to test a transit time measuring device in this way.

[0029] In a preferred aspect of the method according to the invention, the gradient of one or more temporal changes in the length of the path is adjusted using one or more valves, the gradient of the dynamics of the one or more corresponding temporal changes in the transit time is determined, and the corresponding adjusted and determined gradients are compared. Since the gradient of a temporal change is a key variable in the analysis of a recorded curve, changing it and comparing pairs of gradients that should correspond to each other is a good way to test the measuring equipment that records the dynamics. The transit time measuring equipment can also be tested more precisely as this compares not only the periodicity of the measurement signal with the actual change, but also another structural feature of the recorded transit times.In runtime curve analyses, various characteristics of a curve can be analyzed. These include, for example, periodicity and / or gradient and / or curvature and / or skewness.

[0030] In a particularly preferred aspect, statistical route parameters are determined from one or more set gradients in the changes in the length of the route. These can be, for example, mean values, variances, or other statistical parameters. After determining the gradients in the changes in the running time, similar statistical running time parameters are determined for the corresponding gradients. Comparing the route parameters with the running time parameters provides a robust option for comparing individual values, since small measurement errors or disturbances in the measurements have less impact on the statistical parameters than on the individual values. This therefore corresponds to a type of filtering of the test results. Since all measurements are inherently subject to measurement errors, such testing can reduce the probability that running time measuring devices fail the test due to errors that are irrelevant to everyday measurements.

[0031] In a further preferred aspect of the method according to the invention, the curvature of one or more temporal changes in the length of the path is adjusted using one or more valves, the curvature of the dynamics of the one or more corresponding temporal changes in the transit time is determined, and the corresponding adjusted and determined curvatures are compared. Since the curvature of a temporal change represents another everyday relevant quantity in the analysis of curves, changing it and comparing pairs of curvatures that should correspond to each other is another possibility for testing transit time measuring devices.

[0032] In a particularly preferred aspect, statistical path parameters are determined from one or more set curvatures in the changes in the path length. These can again be mean values, variances, or other statistical parameters. After determining the curvatures in the changes in the runtime, similar statistical runtime parameters are determined for these. Comparing the path parameters with the runtime parameters represents a further robust variant for comparing individual values. This therefore again corresponds to a type of filtering of the test results. In a further preferred aspect of the invention, one or more path limit values ​​are determined for the temporal changes in the path length. These can be, for example, oscillation centers (half the amplitude of a periodic signal) or other percentage values ​​of the amplitude, but also other values.The points in time at which the length of the route exceeds and / or falls below one or more route limit values ​​are then preferably determined. The corresponding transit time limit values ​​are determined, and then the points in time at which the temporal changes in the transit time exceed and / or fall below these transit time limit values ​​are determined. After pairs of corresponding points in time have been formed, these can be compared with each other. This allows for a very sensitive investigation of the temporal resolution of the transit time measuring device. In particular, the fine structures of the measurement can be tested in great detail. Limit value analyses play a major role, for example, in the determination of intracranial pressure and intracranial compliance using non-invasive transit time measurements, so the method according to the invention is particularly suitable for transit time measuring devices used in medical fields.

[0033] To the extent that this brief description of the disclosure describes features that are not listed in the patent claims, these features do not represent essential features in the sense that these features must necessarily be included in the patent claims, but these features are particularly prominent preferred implementations of the claimed invention, can be combined with any of the patent claims, and can also be combined with each other as desired.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The following description of preferred embodiments serves to explain the invention. They show:

[0036] Fig. 1 shows a system according to the invention with a fluid circuit comprising a pump and a pressure vessel made of an elastic material. A transit time measuring device is attached to the pressure vessel.

[0037] Fig. 2 shows a system according to the invention with a first controllable valve installed in the fluid circuit. Fig. 3 shows a system according to the invention with a second controllable valve installed in the fluid circuit.

[0038] Fig. 4 shows a system according to the invention with a force sensor or a device for measuring running distance.

[0039] Fig. 5 an illustration of various design options of the preferably variable-volume pressure vessel

[0040] Fig. 6 a measurement of the transit time of an ultrasonic signal, a measurement of the force exerted by the pressure vessel and a measurement of the distance between two opposite walls of the pressure vessel.

[0041] Fig. 7 is a process diagram illustrating the method according to the invention.

[0042] Components shown in several figures have the same reference symbols.

[0043] DETAILED DESCRIPTION

[0044] Figure 1 shows a schematic representation of the system according to the invention. The system is suitable for testing a transit time measuring apparatus 1 and comprises: a fluid circuit 2, comprising: a pressure vessel 3, which comprises at least one movable surface element, and a pump 4, wherein the pressure vessel 3 and the pump 4 are designed to interact in such a way that time-dependent changes in the length of a path 5 between one section of the surface element 9 and another section of the pressure vessel 10, over which path 5 the transit time is to be measured, are effected.

[0045] The pressure vessel may have a variable volume and / or be made of elastic material. A transit time measuring device 1 to be tested may be detachably attached to the pressure vessel 3.

[0046] The pump 4 is designed to pump the fluid in circuit 2. As soon as the pump 4 is activated and begins to pump the fluid in circuit 2, the volume of the pressure vessel 3 can increase and decrease again, for example the pressure vessel 3 can expand and contract again. In this way, the length of the path 5 between one section of the movable surface element and another section of the pressure vessel 3 changes. In particular, it is clear that any section of the pressure vessel can represent the surface element and the rest of the pressure vessel forms the other section. The selection of the section of the surface element is equally arbitrary. The running time, which is to be measured over the path 5 and recorded by the running time measuring device, also changes as the path 5 changes.The frequency and all other properties of these changes are completely determined by the properties of the pressure vessel 3 and the pump 4 (pump speed, etc.). Therefore, the transit time measuring device 1 can be tested on the system.

[0047] Figure 2 additionally shows a first controllable valve 6 introduced into the fluid circuit 2. The first controllable valve 6 is introduced into the fluid circuit 2 in such a way that it can inhibit the outflow of fluid from the pressure vessel 3. If the valve remains closed, the volume of the pressure vessel 3 continues to increase while new fluid is pumped into the pressure vessel 3 by the pump 4. As soon as the first controllable valve 6 is opened, the overpressure in the pressure vessel 3 ensures that the excess fluid flows back into the rest of the circuit 2 and the volume of the pressure vessel 3 decreases again. Depending on the opening and closing of the first controllable valve 6, the length of the path 5 therefore also changes. The valve 6 can be designed in various ways. In a preferred embodiment, the valve 6 can be opened and closed again at a predetermined frequency.For example, the pulsatile blood flow of a human can be simulated if the fluid circuit 2 is intended to mimic the blood circulation and the pressure vessel 3 the human skull, if the transit time measurement device 1 being tested is intended for use on humans, for example, to determine or categorize intracranial pressure or intracranial compliance. The recorded transit time measurements (plotted over time, referred to as a transit time curve) then also contain a periodic structure. Analyzing the frequency of the transit time curve thus allows direct testing of the transit time measurement device. In particular, the amplitude of the temporal change in the distance can also be varied through suitable interaction of the pump and the valve. This is also reflected in the structure of the transit time curve.In this way, the transit time measuring apparatus 1 can be tested not only for its temporal but also for its spatial resolution. In a further preferred embodiment, the valve 6 is designed so that the degree of opening of the valve 6 can assume different values. In this way, the rate of change in the volume of the pressure vessel 3 and thus the rate of change in the length of the section 5 over which the transit time is to be measured is adjusted. This is equivalent to adjusting the gradient of the section curve (temporal change in the section). Since the section and the transit time are linearly related to one another, the adjusted gradient is also reflected in the transit time curve. The system therefore allows the transit time measuring apparatus to be tested not only with regard to the change in the length of the section itself, but also with regard to the first-order dynamics of this change.In a further embodiment of the invention, the opening and closing speeds of valve 6 are adjustable. This allows the acceleration of the change in the volume of the pressure vessel and thus also the acceleration of the change in the length of the section 5 over which the transit time is to be measured to be adjusted. This adjusts the curvature of the section curve. Due to the linear relationship, this is also reflected in the transit time curve if the measurement is carried out correctly, so that second-order dynamics can also be tested in the measurements of the transit time apparatus 1.

[0048] Figure 3 additionally shows a second controllable valve 7 introduced into the fluid circuit 2. This second controllable valve 7 is introduced into the fluid circuit 2 in such a way that it enables a parallel outflow of the fluid from the pressure vessel 3 to the first controllable valve 6. Independent use (opening and closing) of both valves now allows, for example, the reproduction or simulation of regular pulses (first or second controllable valve) and irregular intermediate beats (second or first controllable valve) of a human heart. In particular, this also allows superpositions of different frequencies to be set. In this way, both the temporal and spatial structure of the path curve can be changed. When a first low frequency is superimposed on a second high frequency, for example,Medically relevant cases such as atrial fibrillation can be simulated, i.e. a dominant change in the temporal structure of the path curve. In addition, the second frequency can, for example, be exactly half the first frequency, so that every second opening of the first valve results in a simultaneous opening of the second valve. This changes the outflow of fluid from the pressure vessel, resulting in a spatial change in the structure of the path curve. These changes should also be reflected in the transit time curve, so that further testing options are possible. The second valve could also be controlled so that it opens while the first valve is open, but for a shorter or longer duration. In this way, the curvature of the path curve can be changed discretely. This enables corresponding tests for the transit time measuring apparatus.Furthermore, it is possible to open and close the independently controllable valves 6 and 7 depending on the respective applied pressure. In a preferred embodiment, the first controllable valve is set so that it opens and closes again at a fixed pressure in the fluid. The second controllable valve, on the other hand, is designed to open at different levels of the applied pressure, depending on the control. The second controllable valve is controlled so that the variably adjustable opening pressure of the valve changes randomly. This can cause irregular disturbances in the path curve, which can be used, for example, to simulate cardiac arrhythmias or extrasystoles in humans. Accordingly, transit time measuring devices intended for use in the medical field can be tested.

[0049] Figure 4 also shows a further measuring device 8. This measuring device can be a device for measuring the travel distance 5. Furthermore, the measuring device can be a force sensor, which records the force exerted by the pressure vessel on the sensor during expansion and the release of this force during contraction. Using such a device, the distance curve or a representative substitute curve (hereinafter also referred to as the distance curve) can be recorded. The analysis of the recorded distance curve and the travel time curve can enable further tests of the travel time measuring apparatus. In a particularly preferred aspect of the invention, statistical parameters are preferably determined from the recorded distances in order to make the previously described tests more robust. With periodic opening and reclosing of one or more valves, a likewise periodic temporal structure of the distance curve arises.The recurring elements of this structure (peaks, plateaus, etc.) can thus be summarized using statistical parameters. For example, a mean value (or variance, etc.) of an initial gradient of all recorded periods can be calculated. The same operation can also be performed on the runtime curve, resulting in characteristic path and runtime values. Comparing these values ​​with each other constitutes a further test for the runtime measuring apparatus 1, which is more robust to small disturbances than individual measurements. This can be desirable if external disturbances during testing could otherwise falsify the test result. The described operation therefore amounts to a type of filtering of the measurement. In a further preferred aspect of the invention, certain limit values ​​of the path curve are defined.This could, for example, be the oscillation center of a periodic change in the length of the track, i.e. a kind of zero line comparable to the zero line of a sine oscillation, or a characteristic value that represents a certain signal height compared to the maximum amplitude (e.g. 70% of the maximum amplitude above the oscillation center). A first group of time points is then generated, with each time point at which the track curve exceeds and / or falls below the limit value being assigned to this first group of time points. Corresponding limit values ​​are also used for the runtime curve to assign the corresponding time points to a second group of time points. Pairs of corresponding time points (time points based on the same phenomenon) are created between the two groups of time points.This assignment constitutes a first new test of time-of-flight measurement device 1, since the absence of a time point corresponding to a time point assigned to the first group in the second group of time points indicates erroneous measurements by time-of-flight measurement device i. Furthermore, the complete pairs of time points can be compared internally. This enables a sensitive testing of the temporal resolution of time-of-flight measurement devices i.

[0050] Figure 5 shows four different embodiments of a variable-volume pressure vessel 3. In a preferred embodiment (Fig. 5a), the pressure vessel 3 consists of an elastic material and is designed to expand or contract preferably isotropically in response to internal pressure changes. The isotropic volume change of the pressure vessel 3 allows for better handling of the system, since precise positioning of time-of-flight measuring devices 1 is not necessary. The section of the movable surface element 9 of the pressure vessel 3 is any desired part of the surface (e.g. side wall, ceiling, or floor) of the pressure vessel 3, the other section 10 represents the remainder of the surface (e.g. side wall, ceiling, or floor) of the pressure vessel. In a further preferred embodiment (Fig.5b) the pressure vessel 3 consists of two cups that are placed one inside the other, a first cup and a second cup, which are connected to each other in such a way that the second cup fits into the first cup and has its opening facing the bottom of the first cup. In addition, the edges of the cups are connected to each other using a plastic or other material so that the pressure vessel is leak-tight. The restoring force when the volume changes can be caused by the force of weight (if the cups are arranged vertically). However, the restoring force can also be created, for example, by springs connecting the cups. The second cup and the seal represent the movable surface element 9, and the first cup represents the other section 10 of the pressure vessel. The distance 5 over which the running time is to be measured leads from the bottom of the first cup to the bottom of the second cup.Since no elastic components are installed in this embodiment, the service life of the pressure vessel can be increased. In a further preferred embodiment, the pressure vessel consists of a container whose walls (e.g. side wall, ceiling, or floor), with the exception of one movable wall, are made of non-elastic material. The movable wall is made of elastic material. The movable surface element can completely encompass the movable wall (Fig. 5c). However, it is also possible for the movable surface element to only encompass part of the wall (Fig. 5d). The distance 5 over which the running time is to be measured runs from the movable surface element to the wall of the pressure vessel opposite this movable surface element.Since there are fewer moving parts than in the previously described embodiment, measurement interference is less likely when testing a time-of-flight measurement device. Furthermore, the pressure vessel can be positioned more conveniently than the pressure vessel shown in Figure 5a, allowing a balance to be struck between handling during system setup and handling during system use.

[0051] Figure 6 shows a measurement of the accumulated time of flight of an ultrasonic signal (accToF), a measurement of the force exerted by the pressure vessel during deformation (CAM), e.g., on a section of a movable surface element and another section of the pressure vessel, using a force sensor, and a measurement of the length (“distance”) of the distance between a section of a movable surface element and another section of the pressure vessel, over which the time of flight is to be measured. The accumulated time of flight describes the processed raw data of the time of flight measurement of the ultrasonic signal. Bandpass filters are used to filter out the transmitted non-transmitted interference signals from the received signal, and the resulting signal is further smoothed using statistical processing (averaging, analysis of variance, etc.). When examining the three recorded curves, the correlation between the three measurements is worth highlighting.It is clear that changing the distance results in a parallel change in the running time and force, and that these changes occur simultaneously. The frequency of the change in the length of the distance is also reflected in the change in force and running time. In addition to the frequency of the changes, the speed and acceleration of the change in the length of distance 5, over which the running time is measured, also correlate, albeit somewhat weaker, with the recorded running time measurement. Furthermore, it is clear that the tests described above regarding the formation of limit values ​​and statistical parameters can also be applied to the curves.Control variables other than the length of section 5, which can be used as representative substitute measurements, are also conceivable, such as, in this example, the force exerted by the pressure vessel on a force sensor located on one side of the pressure vessel and connected to the other side via a spring or similar connection. It is clear that the system according to the invention is demonstrably suitable for testing time-of-flight measuring devices.

[0052] Figure 7 shows a process diagram illustrating the inventive method 100 for testing a transit time measuring device using the inventive system, including optional operations. In optional operation 101, the method can begin with adjusting the frequency of the temporal variation of the length of the path 5.

[0053] In the optional operation 102, the gradient of the one or more temporal changes in the length of the path 5 is adjusted by appropriately controlling the one or more valves.

[0054] In the optional operation 103, the curvature of the one or more temporal changes in the length of the path 5 is adjusted by appropriately controlling the one or more valves.

[0055] In operation 104, a signal is sent over the path 5 over which the transit time is to be measured.

[0056] In operation 105, the signal is received after it has passed through the path 5 over which the propagation time is to be measured.

[0057] In operation 106, the propagation time of the signal over path 5 is determined.

[0058] In operation 107, the length of the section 5 over which the running time is to be measured is changed by suitable interaction of pressure vessel and pump.

[0059] In the optional operation 108, the change in the length of the section 5 is effected by suitable interaction of the pressure vessel, pump and one or more valves.

[0060] Operations 101 to 108 can be repeated any number of times. The optional operations 101 to 103 and 108 can be executed again or omitted in each iteration.

[0061] In the optional operation 109, the frequency or frequencies of the temporal changes in the specific runtimes are determined.

[0062] In the optional operation 110, the frequency(ies) set in the optional operation 101 and those determined in the optional operation 109 are compared to test the transit time measuring apparatus 1. In the optional operation 111, the gradient(s) of the temporal changes in the determined transit times are determined.

[0063] In the optional operation 112, the gradient(s) set in the optional operation 102 and the gradient(s) determined in the optional operation 111 are compared with each other in order to test the runtime measuring apparatus 5.

[0064] In the optional operation 113, the curvature or curvatures of the temporal changes in the specific runtimes are determined.

[0065] In the optional operation 114, the curvature(s) set in the optional operation 103 and the curvature(s) determined in the optional operation 113 are compared with each other in order to test the travel time measuring apparatus 5.

[0066] In the optional operation 115, statistical route characteristics, such as mean values, variances, etc. of signal characteristics such as gradients, curvatures, etc., are formed from the changes in the length of the route 5.

[0067] In the optional operation 116, statistical runtime characteristics, such as mean values, variances, etc. of signal characteristics such as gradients, curvatures, etc., are formed from the changes in the determined runtimes, which correspond to the route characteristics formed in the optional operation 115.

[0068] In the optional operation 117, the path characteristics formed in the optional operation 115 are compared with the corresponding runtime characteristics formed in the optional operation 116 in order to test the runtime measuring apparatus 1.

[0069] In the optional operation 118, one or more path limit values ​​are formed from the changes in the length of path 5. These limit values ​​can be oscillation centers, percentages of the maximum amplitude, or other values.

[0070] In the optional operation 119, one or more runtime limits corresponding to the route limit values ​​formed in the optional operation 118 are formed from the changes in the determined runtimes. In the optional operation 120, a first group of points in time at which the length of the route exceeds and / or falls below the one or more route limit values ​​is determined.

[0071] In the optional operation 121, a second group of points in time is determined at which the runtime exceeds and / or falls below the one or more runtime limits corresponding to the route limits.

[0072] In the optional operation 122, the time points of the first and second groups are divided into pairs of corresponding time points. Two time points correspond if the reason for their inclusion, i.e., exceeding and / or falling below a threshold value, is based on the same phenomenon in the curves.

[0073] In the optional operation 123, the time points within the pairs are compared to test the time-of-flight measuring apparatus 1.

[0074] The various aspects and embodiments described above may be combined to create yet further embodiments. These and other changes may be made to the embodiments in light of the above detailed description. In general, the terms used in the following claims should not be construed to limit the claims to the specific aspects and embodiments disclosed in the description and claims, but rather to encompass all possible embodiments, along with the full scope of equivalents to which such claims are entitled.

[0075] REFERENCE SYMBOL

[0076] Transit time measuring apparatus i Fluid circuit 2

[0077] Pressure vessel 3

[0078] Pump 4

[0079] Distance over which a running time is to be measured 5

[0080] First valve 6 Second valve 7

[0081] Additional measuring device 8

[0082] Movable surface element 9

[0083] Other section of the pressure vessel io

Claims

CLAIMS 1. A system for testing a transit time measuring apparatus (1), the system comprising: a fluid circuit (2), the fluid circuit comprising: a pressure vessel (3) which comprises at least one movable surface element, and a pump (4), wherein the pressure vessel (3) and the pump (4) are designed to interact in such a way that time-dependent changes in the length of a path (5) between a section of the surface element (9) and another section of the pressure vessel (10), over which path (5) the transit time is to be measured, are effected.

2. A system according to claim 1, wherein the fluid circuit comprises one or more controllable valves, wherein the pressure vessel (3), the pump (4) and the one or more valves are designed to cooperate in such a way that the time-dependent changes in the length of the path (5) between the section of the surface element (9) and the other section (10) of the pressure vessel, over which path (5) the running time is to be measured, are effected.

3. A system according to claim 2, wherein at least one of the one or more controllable valves is configured to be opened and closed again at a predetermined frequency.

4. A system according to claim 2 or 3, wherein at least one of the one or more controllable valves opens and closes automatically in dependence on the pressure in the fluid at the at least one valve.

5. A system according to any one of claims 2-4, wherein the one or more controllable valves comprise at least a first controllable valve (6) and a second controllable valve (7).

6. A system according to claim 5, wherein the first controllable valve (6) and the second controllable valve (7) can be controlled independently.

7. A system according to claim 5 or 6, wherein the first controllable valve (6) is designed to open and close again at a first frequency and the second controllable valve (7) is designed to open and close again at a second frequency different from the first frequency.

8. A system according to claim 5 or 6, wherein the first controllable valve (6) is designed to open and close again automatically in dependence on a pressure present in the fluid at the first controllable valve and the second controllable valve (7) is designed to open and close again automatically in dependence on a pressure present in the fluid at the second controllable valve.

9. A system according to any one of claims 2-8, wherein the one or more controllable valves are adapted to be controlled via electronic or electromagnetic signals.

10. A system according to any one of claims 2-9, wherein the one or more controllable valves are designed to open at different opening speeds and close at different closing speeds.

11. A system according to any one of claims 2-10, wherein the one or more controllable valves are designed to allow different degrees of opening.

12. A system according to any one of claims 2-11, wherein the system comprises an external control unit configured to control the one or more controllable valves.

13. A system according to any one of the preceding claims, wherein the pressure vessel (3) comprises one or more walls, preferably ceiling, floor and side wall, and the at least one movable surface element (9) and / or the other section of the pressure vessel (10) comprises at least one of the walls of the pressure vessel (3).

14. A system according to any one of the preceding claims, wherein the pressure vessel (3), preferably the surface element (9) and / or the other Section (10) of the pressure vessel (3) is made of elastic material.

15. A method (100) for testing a transit time measuring apparatus (1) using the system according to any one of the preceding claims, the method comprising: sending (104) a signal over the path, Receiving (105) the signal after passing through the route, Determining (106) the propagation time of the signal over the path, characterized by Time-dependent change (107) of the length of the section by means of the interaction of the pressure vessel and the pump.

16. A method according to claim 15, wherein: the time-dependent changing of the length of the path occurs by means of cooperation of the pressure vessel, the pump and the one or more valves (108).

17. A method according to any one of claims 15-16, the method comprising: transmitting the signal through a medium, and Changing the physical state of the medium.

18. A method according to any one of claims 15-17, the method comprising: Setting (101) the frequency of the temporal changes in the length of the route, determining (109) the frequency of the temporal changes in the running time, and comparing (110) the set and determined frequencies for testing the running time measuring apparatus.

19. A method according to any one of claims 15-18, the method comprising: Setting (102) the gradient of one or more temporal changes in the length of the route, Determining (111) the gradient of one or more corresponding temporal changes in the running time, and Comparing (112) the corresponding set and determined gradients for testing the transit time measuring apparatus.

20. A method according to any one of claims 15-19, the method comprising: Setting (102) the gradients of one or more temporal changes in the length of the route, Forming (115) one or more statistical route characteristics of the set one or several gradients of the temporal changes in the length of the route, determining (112) the gradients of one or more corresponding temporal changes in the running time, Forming (116) one or more statistical running time characteristics of the determined one or more gradients of the temporal changes in the running time, and Comparing (117) the one or more path characteristics with the corresponding one or more travel time characteristics for testing the travel time measuring apparatus.

21. A method according to any one of claims 15-20, the method comprising: Adjusting (103) the curvature of one or more temporal changes in the length of the route, Determining (113) the curvature of one or more corresponding temporal changes in the transit time, and Comparing (114) the corresponding set and determined curvatures for testing the transit time measuring apparatus.

22. A method according to any one of claims 15-21, the method comprising: Adjusting (103) the curvatures of one or more temporal changes in the length of the route, Forming (115) one or more statistical route characteristics of the set one or more curvatures of the temporal changes in the length of the route, determining (112) the curvatures of one or more corresponding temporal changes in the running time, Forming (116) one or more statistical travel time characteristics of the determined one or more curvatures of the temporal changes in the travel time, and comparing (117) the one or more distance characteristics with the corresponding one or more travel time characteristics for testing the travel time measuring apparatus.

23. A method according to any one of claims 15-22, the method comprising: Forming (118) one or more route limit values ​​for the temporal changes in the length of the route, Determining (120) a first group of points in time at which the length of the route has exceeded and / or fallen below the one or more route limit values, forming one or more corresponding runtime limit values ​​for the temporal changes in the runtime (119), Determining (121) a second group of points in time at which the runtime has exceeded and / or fallen below the one or more runtime limit values, Forming (122) pairs of corresponding times between the first and second group, and Comparing the time points within the pairs of corresponding time points to test the transit time measuring apparatus (123).

24. The use of a system according to claims 1 to 14 for testing a transit time measuring apparatus (1).

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