Sensor for container interiors

Abstract

The invention relates to the field of measurement technology and concerns a container interior sensor, such as those which can be used to measure the fill level in liquid hydrogen tanks for example. The aim of the invention is therefore to provide a sensor for container interiors, in particular for containers for cryogenic liquids, which operates more efficiently and provides more accurate measurement results. This is achieved by a container interior sensor which is equipped with at least one piezoelectric substrate, at least one acoustic transducer component and at least one electrical waveguide, said electrical waveguide having, at one end, at least one antenna and / or at least one transmission line and, at the other end, at least one terminating element.

Description

[0001] Sensor for container interiors

[0002] The invention relates to the field of measurement technology and concerns a sensor for container interiors, such as can be used, for example, in liquid hydrogen tanks or in other containers, storage tanks, heat exchangers, pumps, or other fluidic components which are at least partially filled, but in particular for liquids at low temperatures or in the cryogenic range, for measuring the fill level or the temperature.

[0003] Liquefied or compressed gases such as carbon dioxide, ammonia, chlorine, anhydrous sulphurous acid, phosgene, nitrous oxide, acetylene, mine gas, illuminating gas, hydrogen, oxygen, nitrogen and air are commercially available and widely used.

[0004] Liquid hydrogen is the liquid state of the element hydrogen. Hydrogen naturally occurs in the molecular Fh form. To exist as a liquid, H2 must be cooled below its critical point of 33 K (Wikipedia, keyword liquid hydrogen). Hydrogen storage is the reversible storage of hydrogen with the goal of preserving its chemical and physical properties for future use. Storage includes the processes of storage or storage loading, temporary storage, and withdrawal or storage discharge. Conventional methods of storing hydrogen are compressed gas storage in pressure vessels by compression with compressors and liquefied gas storage in liquefied form by cooling and compression.

[0005] Large amounts of energy are required not only for the production of cryogenic liquids from gases, but also for their storage (compression accounts for approximately 12%, liquefaction for approximately 20% of the stored energy). The energy required for this can be broken down into the following components, each based on the stored energy content:

[0006] - 28 to 46% for liquefaction depending on the quantity and method used,

[0007] - 6% for transport between liquefaction station and filling station,

[0008] - up to 3% per day (% / d) due to boil-off losses, and

[0009] - Evaporation losses during transfer.

[0010] Therefore, careful handling during the production and storage of cryogenic liquids is important for economic use.

[0011] When storing compressed gas in the form of cryogenic liquids, pressure is not a problem for the tank design. However, considerable effort is required for thermal insulation of the tank and pipes. Advantages include the lower reactivity of cryogenic liquids at low temperatures and the 800-fold higher density of liquid hydrogen (LH2) compared to gaseous hydrogen at ambient pressure. Storage tanks for LH2 are established worldwide. Atmospheric tanks, in which the liquid is cryogenically cold at 20.3 K, are the most common.

[0012] All tanks, containers or storage facilities for liquids and gases usually contain a variety of sensors, in particular sensors for measuring the fill level, temperature, pressure, etc. inside or outside the tanks, containers or storage facilities.

[0013] According to WO 2004 / 074782 A2, an ultrasonic level gauge is known for the continuous and point-by-point detection of the liquid level in a closed container or pipeline with an inaccessible internal volume, in such a way that it measures through the container wall. However, special requirements must be met for level measurement or the measurement of other information from cryogenic liquids. The known methods for such level measurements are based on electrical resistance measurements and introduce heat into the cryogenic liquid with each measurement. The level gauges are a source of evaporation losses in such containers.

[0014] Therefore, level gauges were developed that contain acoustic components and use transit time measurement in a fluid.

[0015] According to WO 98 / 57163 A, the measurement of physical or technical quantities of viscous media using Rayleigh waves is known. The device for this purpose consists of an acoustic transmission system (transmitter-measuring section-receiver) in which the measuring section is made of a non-piezoelectric material and can be brought into at least partial contact with the medium to be measured. The device for generating Rayleigh waves and / or the device for detecting Rayleigh waves, on the one hand, and the measuring section, on the other, are separate components.

[0016] According to US 2008 / 0104969 A1, an acoustic sensor for cryogenic containers is known that is positioned to detect the resonant frequency of the container and the liquid contents therein. The acoustic sensor is positioned on the exterior or in intermediate layers of the cryogenic container, since any direct contact of the cryogenic liquid with the exterior of the cryogenic container initiates a potential heat path, allowing heat to enter the container and reducing the efficiency of the cryogenic container.

[0017] As further developments, acoustic sensors for level measurements were also implemented in cryogenic containers.

[0018] According to DE 10 2021 110 168 A1, level measurement can be implemented using acoustoelectronic components in cryogenic containers. The level sensor used transmits its measured values ​​contactlessly, advantageously via capacitive, inductive, and / or wireless transmission, from within the storage tank, and these values ​​can also be queried contactlessly there. The acoustoelectronic components use surface acoustic waves (SAW) to sensitively detect the phase boundary between the liquid and gas phases. In contrast to established resistance measurement methods, virtually no heat is introduced into the liquid hydrogen.

[0019] A disadvantage of the prior art solutions is that sensors for containers, particularly for cryogenic containers, such as level sensors, are mounted either on the outside or inside of the container and in both cases must transmit the signals through the container wall. When measuring on the outside of the container, the fill level cannot be determined very accurately because the materials and structure of the container wall influence the transmissibility of the signals. With the thermally highly insulated walls of cryogenic containers, the acoustic waves must be transmitted through the container wall. Since the insulated wall has a vacuum in one space, acoustic waves are blocked and cannot be transmitted to the outside.

[0020] If the sensors are located inside the tank, data such as fill level, temperature, or pressure can be determined very precisely. However, according to current technology, the signals still have to be routed through the tank wall via cabling. This generally negatively impacts the thermal balance as well as the interior of the tank and the media stored therein. When storing cryogenic liquids, this leads to undesirable heat input and can thus also lead to undesirable evaporation, pressure increase, or leakage of the cryogenic liquids.

[0021] If the sensors are arranged on the outer wall of the containers, the measurement must be taken through the container wall, which, particularly in the case of cryogenic containers, leads to a failure of the measurement method or at least to inaccurate data due to the design of the container wall.

[0022] All known solutions are unsatisfactory in terms of the efficiency and accuracy of sensor measurements.

[0023] The object of the present invention is therefore to provide a sensor for container interiors, in particular for containers for cryogenic liquids and / or fluids, which operates more efficiently and provides more accurate measurement results.

[0024] The object is achieved by the invention defined in the claims. Advantageous embodiments are the subject of the dependent claims, whereby the invention also includes combinations of the individual dependent claims in the sense of an AND connection, as long as they are not mutually exclusive.

[0025] In the sensor according to the invention for container interiors,

[0026] - at least one acoustic transducer component and at least one electrical waveguide are arranged on at least one piezoelectric substrate and / or on a piezoelectric layer on a non-piezoelectric substrate and / or on a non-piezoelectric superstrate on a piezoelectric layer, or

[0027] - at least one piezoelectric substrate and / or at least one electrical conductor structure and at least one acoustic transducer component are arranged on at least one electrical waveguide and / or on a piezoelectric layer on a non-piezoelectric substrate and / or on a non-piezoelectric superstrate with a piezoelectric layer, and

[0028] - in which all acoustic transducer components can be excited with the same or different wavelengths, and

[0029] - wherein the acoustic transducer component is at least functionally connected to the electrical waveguide and the electrical waveguide is at least functionally connected at one end to at least one antenna and / or at least one transmission line,

[0030] - and in the case of the presence of more than one acoustic transducer component, all acoustic transducer components are at least functionally connected to the electrical waveguide,

[0031] - and at the end of the electrical waveguide facing away from the antenna and / or the transmission line, at least one terminating element is at least functionally connected to the electrical waveguide,

[0032] - and in the case of the presence of an antenna on the sensor, signals are transmitted wirelessly between the antenna on the sensor and an antenna of an electronic component, whereby the electronic component with its antenna is not in direct contact with the liquid and / or fluids in the container,

[0033] - and in the case of the presence of at least one transmission line, this is led from the at least one electrical waveguide to at least one coupling element and / or at least one electronic component outside the container for evaluating the measurement signals of the sensor,

[0034] - and in the case of the presence of at least one transmission line and at least one coupling element, at least one further transmission line is routed from the at least one coupling element to the at least one electronic component outside the container for evaluating the measurement signals of the sensor, - and in the case of the presence of at least one transmission line and at least one coupling element, at least one antenna-based radio transmission is routed between the coupling element and the at least one electronic component outside the container for evaluating the measurement signals of the sensor,

[0035] - and in the case of the presence of an antenna on the sensor, signals are transmitted by radio between the antenna on the sensor and an antenna of a coupling element and at least one transmission line is led from the at least one coupling element to the at least one electronic component outside the container for evaluating the measurement signals of the sensor.

[0036] Advantageously, the substrate and / or superstrate on which the at least one electrical waveguide and the at least one acoustic transducer component are arranged or which is arranged on an electrical waveguide is a plate or a film or a microchip made of glass / glasses / ceramic / ceramics, such as SiO2, Al2O3, SiA4, TiN, SiN, borosilicate glass, or of piezoelectrics, such as quartz, LiNbOa, black-LiNbOa, yellow-black LiNbOa, LiTaOs, AIN, Sc-AIN, ZnO, CTGS, langasite, gallium orthophosphate, PZT, PMN-PT, PVDF, or of metals / metal alloys, such as Al, Cu, Ti, Ta, TiAl, CuTi, or of polymers, such as PMMA, PTFE, PEEK, polyimide, PET, COP, PDMS, PC, COC, polycaprolactone, PS, or of photoresists, such as SIIEX, ADEX, TMMF S2045, Ordyl, SU-8, or semiconductors such as Si, GaAs, InAs, GaN,or from combinations of these materials and / or in which a layer of the said materials is present as substrate and / or superstrate on a non-piezoelectric substrate, wherein the acoustic transducer components are advantageously arranged on the waveguide, the substrate, superstrate and / or the layer in a cascade-like manner or one behind the other or in a row or parallel to each other or as an array.

[0037] Likewise advantageously, the electrical waveguide is a ribbon cable made up of two strands or wires or a coaxial cable or electrical conductors in the form of planar, coplanar, triplate, slot, hollow and strip lines or combinations of such electrical conductors or periodic conductor structures, alone or on a carrier or substrate or superstrate, wherein even more advantageously the carrier is a dielectric or an insulating body made of glass / glasses / ceramic / ceramics, such as SiOa, Al2O3, SiA1N4, or of polymers, such as PMMA, PTFE, PEEK, polyimide, PET, or of glass fabric or paper, such as FR2, FR3, FR4, CEM1, CEM3. Furthermore advantageously, the at least one electrical waveguide consists of an electrically conductive material, such as copper, aluminum, titanium, platinum or alloys with at least one electrically conductive material.

[0038] And also advantageously, a variety of acoustic transducer components, such as 2 to 200, are available.

[0039] It is also advantageous if the acoustic transducer component(s) are provided for the excitation and / or reception of surface waves, plate waves and / or bulk waves.

[0040] It is also advantageous if one or more acoustic transducer components are present with which acoustic wavelengths smaller than 1 mm, advantageously between 1 pm and 500 pm, are excited.

[0041] It is also advantageous if, in the case of several acoustic transducer components, all are excited with the same wavelength and / or mode or one or more of the acoustic transducer components are excited with a different wavelength and / or mode.

[0042] It is also advantageous if the acoustic transducer component(s) is / are a resonator and / or a delay line.

[0043] It is also advantageous if there is an antenna for each sensor in the container.

[0044] It is also advantageous if the transmission line is a cable which transmits measurement signals from the sensor for the interior of the container to an electronic component for evaluation inside and outside the container in which the sensor for the interior of the container is arranged, wherein the cable is even more advantageously a micro cable made of a material with little to no thermal conductivity, such as advantageously PVC or PFA as dielectric and gold, silver or SS304 CrNi steel as conductor.

[0045] It is further advantageous if the transmission line is routed as a cable within the container to the inside of the container wall and is connected there to a coupling element, at least functionally for transmitting the measurement signals and transmitting the measurement signals to the outer wall of the container and further to an electronic component for evaluation. It is even more advantageous if the coupling element is a capacitive or inductive component for thermally insulated transmission of the measurement signals from the sensor for container interiors from the inside of the container to the outside of the container. It is also advantageous if the fill level of liquefied and / or compressed gases, such as carbon dioxide, ammonia, chlorine, anhydrous sulfurous acid, phosgene, nitrous oxide, acetylene, mine gas, illuminating gas, hydrogen, oxygen, nitrogen, air, and / or cryogenic liquids and / or fluids, can be measured.

[0046] It is also advantageous if the sensor is functionally connected to an electronic component for evaluation, to which other sensors in the same or other containers are functionally connected.

[0047] The solution according to the invention provides for the first time a sensor for container interiors, in particular for cryogenic liquids and / or fluids, which operates more efficiently and provides more accurate measurement results.

[0048] This is achieved by a sensor for the interior of the container, in which

[0049] - at least one acoustic transducer component and at least one electrical waveguide are arranged on at least one piezoelectric substrate and / or on a piezoelectric layer on a non-piezoelectric substrate and / or on a non-piezoelectric superstrate on a piezoelectric layer, or

[0050] - at least one piezoelectric substrate and / or on a piezoelectric layer on a non-piezoelectric substrate and / or on a non-piezoelectric superstrate on a piezoelectric layer and at least one electrical conductor structure and at least one acoustic transducer component are arranged on at least one electrical waveguide.

[0051] It is advantageous for the solution according to the invention if, as substrate and / or superstrate on which the at least one electrical waveguide and the at least one acoustic transducer component are arranged or which is arranged on an electrical waveguide, a plate or a film or a microchip made of glass / glasses / ceramic / ceramics, such as SiO2, Al2O3, SiIXL, TiN, SiN, borosilicate glass, or of piezoelectrics, such as quartz, LiNbOa, black-LiNbOa, yellow-black LiNbOa, LiTaOs, AIN, Sc-AIN, ZnO, CTGS, langasite, gallium orthophosphate, PZT, PMN-PT, PVDF, or of metals / metal alloys, such as Al, Cu, Ti, Ta, TiAl, CuTi, or of polymers, such as PMMA, PTFE, PEEK, polyimide, PET, COP, PDMS, PC, COC, polycaprolactone, PS, or of Photoresists such as SUEX, ADEX, TMMF S2045, Ordyl, SU-8, or semiconductors such as Si, GaAs, InAs, GaN,or combinations of these materials and / or a layer of said materials is present as substrate and / or superstrate on a non-piezoelectric substrate and / or superstrate.

[0052] With the mentioned materials for the piezoelectric substrate, superstrate or layer and / or other functional layers, a very good function of the acoustic transducer components is realized.

[0053] A superstrate according to the present invention has a layer on its underside, for example a piezoelectric layer on the underside of a non-piezoelectric superstrate.

[0054] An electrical waveguide is an inhomogeneous medium which, due to its physical properties, bundles a wave in such a way that it is guided as a traveling wave (Wikipedia, keyword waveguide).

[0055] Advantageously, the electrical waveguides are a ribbon cable made of two strands or wires or a coaxial cable or electrical conductors in the form of planar, coplanar, triplate, slot, hollow and strip lines or combinations of such electrical conductors or periodic conductor structures, alone or on a carrier or substrate, wherein again advantageously the carrier is a dielectric or an insulating body made of glass / glasses / ceramic / ceramics, such as SiO2, AI2O3, SiaN4, or of polymers, such as PMMA, PTFE, PEEK, polyimide, PET, or of piezoelectrics such as quartz, LiNbOa, black-LiNbOa, yellow-black-LiNbOa, LiTaOs, AIN, Sc-AIN, ZnO, CTGS, langasite, gallium orthophosphate, PZT, PMN-PT, PVDF, or of glass fabric or paper, such as FR2, FR3, FR4, CEM1, CEM 3 is present.

[0056] Furthermore, the at least one electrical waveguide can advantageously consist of an electrically conductive material, such as copper, aluminum, titanium, platinum or alloys with at least one electrically conductive material.

[0057] It is also advantageous if the sensor according to the invention has a large number of acoustic transducer components, such as 2 to 200. The number of acoustic transducer components can depend on the height of the interior of the container that is filled with the liquid and / or fluids for which data are to be determined or signals are to be measured. Likewise, the number of acoustic transducer components can depend on the steps in which the user wishes to check the desired signals, such as the fill level. For example, the sensor according to the invention can only have one acoustic transducer component at the minimum and / or maximum fill level. In this case, however, additional acoustic transducer components could also be present to warn the user shortly before the maximum or minimum fill level is reached.However, it is also possible to arrange one acoustic transducer component per centimeter, decimetre, or meter of fill level on the sensor according to the invention. In principle, however, the maximum or minimum fill level, or a desired fill level, can also be indicated with just one acoustic transducer component.

[0058] The arrangement of multiple acoustic transducer components on the substrate and / or the layer and / or the carrier and / or the electrical waveguide can advantageously be cascaded, arranged one behind the other, in a row, parallel to one another, or as an array. This depends on the monitoring of the respective desired data or signals in the container. In this case, the container in which the at least one sensor according to the invention is arranged contains at least one liquid and / or one gas, which can also be referred to as a fluid.

[0059] The acoustic transducer components of the sensor according to the invention consist of one or more acoustic transducers, e.g., interdigital transducers (IDTs) or plate resonators (bulk or shear oscillators) on a piezoelectric substrate and / or on a piezoelectric layer on a non-piezoelectric substrate and / or on a non-piezoelectric substrate on a piezoelectric layer. The dimensions of the IDTs determine the type (mode), frequency, and amplitude of the excited acoustic wave. For example, surface acoustic waves, plate waves, and / or bulk acoustic waves can be excited. Advantageously, the acoustic transducer components of the sensor according to the invention can be used to excite acoustic waves with wavelengths of less than 1 mm, advantageously between 1 pm and 500 pm.

[0060] Advantageously, in the case of a plurality of acoustic transducer components of the sensor according to the invention, all acoustic transducer components can be excited with the same wavelength or one or more of the acoustic transducer components can be excited with a different wavelength.

[0061] Advantageously, in the case of multiple acoustic transducer components of the sensor according to the invention, all acoustic transducer components can be excited with the same mode, or one or more of the acoustic transducer components can be excited with a different mode. It is also advantageous according to the invention if the acoustic transducer component(s) is / are a resonator and / or a delay line.

[0062] Acoustic transducer components utilize the interference of signals of different polarization, mode, or propagation time, realized with the piezoelectric effect. An acoustic wave, such as a surface wave, plate wave, and / or bulk wave, is generated on and / or in a piezoelectric substrate or layer by an IDT. This wave propagates on the surface and / or in the volume of the transducer component and / or in liquids and / or fluids or solids and is received by a second and / or the same IDT. The design of the acoustic transducer allows any frequencies, frequency bands, and / or frequency groups of the respective waves to be filtered and tuned. In the case of an acoustic transducer component being a resonator, the acoustic transducer component is tuned to a range near and / or around its resonant frequency and / or its harmonics.

[0063] In acoustic delay lines, the electrical signal is converted into ultrasound using piezoelectric transducers, e.g., an IDT. It is passed through a medium with a defined speed of sound, e.g., the piezoelectric substrate itself, and then converted back into an electrical signal by a second and / or the same IDT. Delay lines can have reflectors in the sound path that reflect the acoustic wave in whole or in part. Such delay lines are used for the time shifting, division, multiplication, and / or temporary storage of a serial signal using the signal propagation time in an electro-acoustic line of a specific length or in an acoustic transmission path. Furthermore, delay lines with local coding can also be used for identification purposes.

[0064] According to the invention, the acoustic transducer component is further connected to at least one electrical waveguide. The at least one electrical waveguide connects the at least one acoustic transducer component at least functionally to the at least one antenna and / or the at least one transmission line. Advantageously, one antenna per sensor according to the invention is present in the container.

[0065] If multiple acoustic transducer components are present, they are all at least functionally connected to the electrical waveguide. Within the context of the present invention, "functionally connected" means that two components are electrically connected to one another, or are connected for the transmission of a wave or data, or for the performance and transmission of the respective function of one component to the other.

[0066] Furthermore, according to the invention, in the case of the presence of more than one acoustic transducer component, all acoustic transducer components are at least functionally connected to the electrical waveguide and in this case at least one terminating element with defined adjustable electrical reflection behavior is at least functionally connected to the electrical waveguide at the end of the electrical waveguide facing away from the antenna and / or the transmission line.

[0067] The terminating element can be an electrically complex-valued resistor, an open line of defined length, a short-circuited line of defined length, a delay line, a capacitance, for example from 5 pF to 500 nF, an inductance, for example from 2 nH to 800 nH, a real electrical resistance, for example from 10 ohms to 200 ohms, each in parallel and series connection and / or combinations thereof.

[0068] The terminating element serves to ensure that the signals are reliably transmitted between the at least one electrical waveguide and the at least one acoustic transducer component at all locations along the at least one electrical waveguide and are routed to the at least one antenna or transmission line. In the advantageous embodiment, the signal amplitude at all positions where acoustic transducer components are located and / or on the electrical waveguide is at least 10% to 90% of the maximum amplitude, which can advantageously be present at the position of the antenna connection or at another position of the sensor according to the invention. However, it is also possible according to the invention that no terminating element is required to achieve reliable signal transmission.

[0069] In an advantageous embodiment, if multiple acoustic transducer components are present, all of the acoustic transducer components operate at different wavelengths. The configuration is advantageously such that the frequencies are not an integer multiple or sub-multiple of each other and / or are within a tolerance range of plus or minus 5% of the integer multiple or sub-multiple. This means that, starting from a frequency of an acoustic transducer component according to the invention, a further acoustic transducer component may not have a frequency that is a multiple or sub-multiple of the frequency of the other sensor, nor may it be too close to the frequency of the other sensor, but rather differ from each other by at least 5%.This means that each acoustic transducer component occupies different frequencies, which can be safely transmitted via the electrical waveguide and routed to at least one antenna or transmission line.

[0070] In a further advantageous embodiment of the use of resonators as acoustic transducer components, each acoustic transducer component has its own operating frequency. Depending on whether this acoustic transducer component is wetted with the liquid or gaseous phase of the fluid, such as liquid hydrogen, its operating frequency, phase, and / or amplitude at the operating frequency, i.e., the signal properties, change. The metrological observation of this operating frequency, phase, and / or amplitude, i.e., its signal properties, provides information about the phase of the fluid present at the acoustic transducer component. It should be noted that, within the scope of the present invention, the term phase denotes a state of the fluid in the container in the sense of an aggregate state, and, secondly, the phase, together with the frequency or amplitude of the transducer component, describes the signal properties.Knowing the spatial position of the acoustic transducer component in a container allows the phase of the fluid and thus the fill level to be measured at that location. A large number of acoustic transducer components at different spatial positions thus allows for discrete measurement of the fill level.

[0071] In a further advantageous embodiment analogous to the preceding embodiment, but using acoustic transducer components according to the delay line principle, a transmitted wave packet is detected at least once with a time delay based on a defined travel distance, such as 0.1 pm to 2000 pm, of the acoustic wave in and / or on the substrate or carrier or waveguide, and its changes in travel times, phases and / or amplitudes upon wetting with the liquid or gaseous fluid phase are evaluated.

[0072] According to the invention, combinations of the principles of the resonator and the delay line can also be used as acoustic transducer components for evaluation.

[0073] After the signals arrive at the antenna, they are transmitted wirelessly to an antenna of an electronic component for evaluating the measurement signals of the sensor according to the invention, wherein in any case the electronic component with its antenna is not in direct contact with the liquid and / or the fluid in the container and / or the container itself.

[0074] However, it is also possible according to the invention for the antenna of the sensor(s) to receive signals from the antenna of an electronic component that is not in direct contact with the liquid and / or fluid in the container. These signals can trigger actions in the sensor, which in turn can lead to the transmission of signals via the sensor's antenna to the antenna of the electronic component. According to the invention, the antennas of the sensors and the electronic component can operate bidirectionally.

[0075] When the signals arrive at the transmission line, the signals are passed to the at least one coupling element or directly to an electronic component for evaluating the measurement signals of the sensor according to the invention, wherein here too the electronic component is not in direct contact with the liquid and / or the fluid in the container.

[0076] The transmission line can advantageously be a cable that transmits measurement signals from the sensor according to the invention to an electronic component for evaluation inside and outside the container in which the sensor according to the invention is arranged. The cable can be a microcable with little to no or no thermal conductivity. Cables with PVC or PFA as the dielectric and gold, silver, or SS304 CrNi steel as the conductor are advantageously used.

[0077] However, it is also advantageous if the transmission line is routed as a cable within the container to the inside of the container wall and is connected there to a coupling element, at least functionally, for transmitting the measurement signals. The measurement signals are then transmitted to the outer wall of the container and further outside the container to an electronic component for evaluation. The coupling element is also advantageously a capacitive or inductive component for transmitting the measurement signals of the sensor according to the invention from the inside of the container to the outside of the container. The coupling element is advantageously arranged in the container wall.

[0078] Advantageously, the coupling element can be two electrical circuits that are electromagnetically coupled and simultaneously thermally isolated from each other. In the inductive case, this is achieved by two coils whose magnetic fields counteract each other and are thermally separated by a vacuum.

[0079] Of particular importance to the invention is that the sensor according to the invention is in at least partial direct contact with the liquid and / or fluid whose fill level is to be measured. However, the sensor according to the invention also operates and sends and receives signals when it is not in direct contact with the liquid and / or fluid in the container, or when neither liquid nor fluid should be present in the container, for example, when the container is empty.

[0080] Liquids and / or fluids in the container may be, in particular but not exclusively, liquefied and / or compressed gases such as carbon dioxide, ammonia, chlorine, anhydrous sulphurous acid, phosgene, nitrous oxide, acetylene, mine gas, illuminating gas, hydrogen, oxygen, nitrogen, air, and / or cryogenic liquids and / or fluids.

[0081] Cryogenic is a term for substances, processes, and properties associated with extremely low temperatures. A liquid is called "cryogenic" when it is cooled below its usual boiling point, down to -90 °C (Wikipedia, keyword "cryogenic"). The sensor according to the invention is particularly advantageous for cryogenic liquids, such as liquid hydrogen.

[0082] A further advantage of the solution according to the invention is that the sensor according to the invention is functionally connected to an electronic component for evaluation, with which further sensors for container interiors in the same or in other containers are functionally connected.

[0083] The sensor according to the invention is a purely passive sensor that operates without any significant input of power or, above all, heat into the liquid and / or fluid in a container. It is particularly important that the sensor according to the invention is in at least partial direct contact with the liquid and / or fluid in the container when in operation. This makes it possible, for example, to determine the fill level, temperature or pressure using acoustic waves, and on the other hand, there is no signal loss of the acoustic wave due to the transmission of the signals through the container wall, which can be acoustically very unfavorable, particularly in containers for cryogenic liquids, as it can be very thick, made of materials with high acoustic and / or electrical damping, layered or evacuated.

[0084] The invention is explained in more detail below using an exemplary embodiment. Example 1

[0085] The sensor according to the invention consists of a waveguide with a length of 150 mm, a width of 20 mm, and a thickness of 1.8 mm, as well as copper conductors arranged on an FR4 carrier. The carrier has two 35 μm thick copper conductors with a width of 1.0 mm, spaced 0.25 mm apart, on a surface over a length of 140 mm. Ten acoustic transducer components are located on the waveguide at a distance of 12 mm, with electrical contact to the waveguide made of 100 μm thick aluminum ball-wedge bond.

[0086] At one end of the waveguide is a terminating element consisting of a 32 ohm resistor in parallel with a 2.3 nF capacitance, located 17 mm from the nearest acoustic transducer component. The antenna connection is via an SMA printed circuit board socket and is located at the end of the waveguide opposite the terminating element, 13 mm from the nearest acoustic transducer component. The acoustic transducer components are surface Rayleigh wave resonators on a quartz substrate with aluminum conductors for forming the IDTs, reflectors, busbars, and surfaces for electrical bonding. They have an operating frequency of 421 MHz with a frequency offset of 70 kHz from each other. Radio transmission is via ISM SMA antennas in the 433 MHz frequency band with a gain of 3 dBi, and transmission via an RG 174 cable to the electronic component.

[0087] The sensor according to the invention continuously monitors the level of liquid hydrogen in the container.

Claims

Patent claims 1. Sensor for container interiors, in which - at least one acoustic transducer component and at least one electrical waveguide are arranged on at least one piezoelectric substrate and / or on a piezoelectric layer on a non-piezoelectric substrate and / or on a non-piezoelectric superstrate on a piezoelectric layer, or - at least one piezoelectric substrate and / or at least one electrical conductor structure and at least one acoustic transducer component are arranged on at least one electrical waveguide and / or on a piezoelectric layer on a non-piezoelectric substrate and / or on a non-piezoelectric superstrate with a piezoelectric layer, and - in which all acoustic transducer components can be excited with the same or different wavelengths, and - wherein the acoustic transducer component is at least functionally connected to the electrical waveguide and the electrical waveguide is at least functionally connected at one end to at least one antenna and / or at least one transmission line, - and in the case of the presence of more than one acoustic transducer component, all acoustic transducer components are at least functionally connected to the electrical waveguide, - and at the end of the electrical waveguide facing away from the antenna and / or the transmission line, at least one terminating element is at least functionally connected to the electrical waveguide, - and in the case of the presence of an antenna on the sensor, signals are transmitted wirelessly between the antenna on the sensor and an antenna of an electronic component, whereby the electronic component with its antenna is not in direct contact with the liquid and / or fluid in the container, - and in the case of the presence of at least one transmission line, this is led from the at least one electrical waveguide to at least one coupling element and / or at least one electronic component outside the container for evaluating the measurement signals of the sensor, - and in the case of the presence of at least one transmission line and at least one coupling element, at least one further transmission line is led from the at least one coupling element to the at least one electronic component outside the container for evaluating the measurement signals of the sensor, - and in the case of the presence of at least one transmission line and at least one coupling element, at least one antenna-based radio transmission between coupling element and the at least one electronic component outside the container for evaluating the measuring signals of the sensor, - and in the case of the presence of an antenna on the sensor, signals are transmitted by radio between the antenna on the sensor and an antenna of a coupling element and at least one transmission line is led from the at least one coupling element to the at least one electronic component outside the container for evaluating the measurement signals of the sensor.

2. Sensor according to claim 1, wherein the substrate and / or superstrate on which the at least one electrical waveguide and the at least one acoustic transducer component are arranged or which is arranged on an electrical waveguide is a plate or a film or a microchip made of glass / glasses / ceramic / ceramics, such as SiO2, Al2O3, SisN4, TiN, SiN, borosilicate glass, or of piezoelectrics, such as quartz, LiNbOa, black-LiNbOa, yellow-black LiNbOa, LiTaOs, AIN, Sc-AIN, ZnO, CTGS, langasite, gallium orthophosphate, PZT, PMN-PT, PVDF, or of metals / metal alloys, such as Al, Cu, Ti, Ta, TiAl, CuTi, or of polymers, such as PMMA, PTFE, PEEK, polyimide, PET, COP, PDMS, PC, COC, polycaprolactone, PS, or from photoresists such as SIIEX, ADEX, TMMF S2045, Ordyl, SU-8, or from semiconductors such as Si, GaAs, InAs, GaN,or combinations of these materials and / or in which a layer of the said materials is present as substrate and / or superstrate on a non-piezoelectric substrate.

3. Sensor according to claim 2, wherein the acoustic transducer components are arranged on the waveguide, the substrate, superstrate and / or the layer in a cascade or one behind the other or in a row or parallel to each other or as an array.

4. Sensor according to claim 1, in which the electrical waveguide is a ribbon cable made up of two strands or wires or a coaxial cable or electrical conductors in the form of planar, coplanar, triplate, slot, hollow and strip lines or combinations of such electrical conductors or periodic conductor structures, alone or on a carrier or substrate or superstrate.

5. Sensor according to claim 4, wherein the carrier is a dielectric or an insulating body made of glass / glasses / ceramic / ceramics, such as SiOa, Al2O3, SiA4N4, or of polymers, such as PMMA, PTFE, PEEK, polyimide, PET, or of glass fabric or paper, such as FR2, FR3, FR4, CEM1, CEM3.

6. Sensor according to claim 1, wherein the at least one electrical waveguide consists of an electrically conductive material, such as copper, aluminum, titanium, platinum or alloys with at least one electrically conductive material.

7. Sensor according to claim 1, wherein a plurality of acoustic transducer components, such as 2 to 200, are present.

8. Sensor according to claim 1, wherein the acoustic transducer component(s) are provided for exciting and / or receiving surface waves, plate waves and / or bulk waves.

9. Sensor according to claim 1, in which one or more acoustic transducer components are present with which acoustic wavelengths less than 1 mm, advantageously between 1 pm and 500 pm, are excited.

10. Sensor according to claim 1, wherein in the case of a plurality of acoustic transducer components all are excited with the same wavelength and / or mode or one or more of the acoustic transducer components are excited with a different wavelength and / or mode.

11. Sensor according to claim 1, wherein the acoustic transducer component(s) is / are a resonator and / or a delay line.

12. Sensor according to claim 1, wherein one antenna per sensor is present in the container.

13. Sensor according to claim 1, wherein the transmission line is a cable which transmits measurement signals from the sensor for the interior of the container to an electronic component for evaluation inside and outside the container in which the sensor for the interior of the container is arranged.

14. Sensor according to claim 13, wherein the cable is a microcable made of a low to non-thermally conductive material, such as advantageously PVC or PFA as dielectric and gold, silver or SS304 CrNi steel as conductor.

15. Sensor according to claim 1, in which the transmission line is guided as a cable within the container to the inside of the container wall and is connected there with a coupling element at least functionally for transmitting the measuring signals and which transmits the measurement signals to the outer wall of the container and then to an electronic component for evaluation.

16. Sensor according to claim 15, wherein the coupling element is a capacitive or inductive component for the thermally insulated transmission of the measurement signals of the sensor for container interiors from the interior of the container to the outside of the container.

17. Sensor according to claim 1, wherein the fill level of liquefied and / or compressed gases, such as carbon dioxide, ammonia, chlorine, anhydrous sulphurous acid, phosgene, nitrous oxide, acetylene, mine gas, illuminating gas, hydrogen, oxygen, nitrogen, air, and / or cryogenic liquids and / or fluids is measurable.

18. Sensor according to claim 1, which is functionally connected to an electronic component for evaluation, with which further sensors in the same or other containers are functionally connected.