Method for operating a fluid sensor device and fluid sensor device

Abstract

Method for operating a fluid sensor device (100) which is designed to determine the height (H) of a surface (O) of a fluid (F) and / or a quality of the fluid (F) in a fluid container (1) by means of at least one sound transducer module (10) which has a plurality of sound transducers provided in a matrix-like arrangement and is designed to emit and receive sound signals into the fluid (F), the method comprising: - emitting a reference sound signal with a reference sound frequency into the fluid (F) by means of the sound transducer module (10), - receiving a reference response signal by means of the sound transducer module (10), wherein the reference response signal is received in response to the transmission of the reference sound signal, - Determining the signal quality of the reference response signal, - determining a damping characteristic of the fluid (F) on the basis of the determined signal quality of the reference response signal, - Adjusting a sound frequency of a measuring sound signal based on the determined signal quality of the reference response signal and on the basis of the determined attenuation characteristic, and - controlling the sound transducer module (10) such that the measuring sound signal with the adapted sound frequency is emitted into the fluid (F) for determining the height (H) of the surface (O) of the fluid (F) and / or the quality of the fluid (F).

Description

[0001] The present invention relates to a method for operating a fluid sensor device and a fluid sensor device designed to determine the height of a surface of a fluid in a fluid container.

[0002] For example, an acoustic measuring device can be used to determine the height of a fluid surface in a fluid container. A sound transducer in the acoustic measuring device can function both as a sound generator and as a sound receiver. To determine the height of the fluid surface in the fluid container, sound pulses or sound signals can be emitted into the fluid to be measured using the sound transducer. The sound pulses or sound signals can be reflected from an interface or surface of the fluid to another medium. Conclusions about the height of the fluid surface in the fluid container can be drawn from the propagation time of the sound pulses or sound signals. The frequencies of the sound signals are preferably in the ultrasound range.

[0003] Furthermore, using the same or a separately provided sound transducer, sound signals can be emitted toward at least one reference reflector arranged in the fluid to determine the speed of sound in the fluid. The speed of sound can be used both to determine the fluid surface and to determine the quality of the fluid.

[0004] For example, DE 10 2014 210 080 A1 discloses a device for determining the height of a fluid surface in a fluid container. The device known therefrom comprises a first sound transducer configured to emit sound signals toward the fluid surface and to receive the signals reflected by the fluid surface, and a second sound transducer configured to emit sound signals toward a reference element arranged in the fluid container and to receive the signals reflected by the reference element. From the sound signals emitted and received by the second sound transducer, a speed of sound within the fluid can be determined, which in turn can be used to determine the height of the fluid surface.

[0005] Furthermore, from DE 10 2014 210 077 A1 a device and a method for determining the height of a fluid surface in a fluid container are known.

[0006] Furthermore, US 5 744 898 A discloses a device with an ultrasonic transducer matrix having an integrated transmitter and receiver circuit.

[0007] Ultrasound devices known from medical technology are disclosed in US 2017 / 0360415 A1, WO 2018 / 077962 A1, US 9 255 910 B2, US 2016 / 0363561 A1 and US 8 689 606 B2.

[0008] Further ultrasound-based measuring devices are known from WO 2017 / 176397 A1, US 4 905 208 A and EP 0 320 695 A1.

[0009] The present invention is based on the object of providing a method for operating a fluid sensor device and a fluid sensor device with which the height of the surface of a fluid in a fluid container can be determined as accurately as possible.

[0010] This object is achieved by a method having the features of independent claim 1 and by a device having the features of independent claim 8. Preferred and advantageous embodiments of the invention are specified in the subclaims.

[0011] The present invention is essentially based on the idea of ​​adapting the sound frequency of the sound signal emitted into the fluid depending on the attenuation characteristics of the sound path in order to improve the measurement accuracy and spatial resolution. In particular, a balance should be struck between high sound frequencies for the highest possible measurement accuracy and low sound frequencies for the lowest possible attenuation of the sound signals. For example, the attenuation of the sound signals is greater at high fill levels, i.e. when the surface of the fluid in the fluid container is high, due to the long sound path or the long measuring distance through the fluid than at low fill levels, i.e. when the surface of the fluid in the fluid container is low. It has been shown that at low fill levels the measurement accuracy and spatial resolution is reduced.Spatial resolution is a higher priority than at higher fill levels, since an insufficient fluid volume is usually more critical than an excessive fluid volume. Accordingly, it is sufficient to use a low sound frequency at high fill levels so that a sufficiently large response sound signal can still be received despite the lower measurement accuracy or spatial resolution. At the same time, measurement accuracy or spatial resolution is of great importance at low fill levels, which is why higher sound frequencies are preferable here.

[0012] Furthermore, the damping characteristics of the sound path can depend on the temperature-dependent viscosity of the fluid, i.e., the nature of the fluid, in the fluid container. Thus, for example, at low temperatures, where the damping of the fluid is greater than at high temperatures, a low sound frequency is preferable, while at high temperatures, where the damping of the fluid is lower than at low temperatures, a high sound frequency is advantageous.

[0013] Consequently, according to a first aspect of the present invention, a method for operating a fluid sensor device is disclosed, which is designed to determine the height of a surface of a fluid and / or a quality of the fluid in a fluid container by means of at least one sound transducer module, which has a plurality of sound transducers provided in a matrix-like arrangement and is designed to emit and receive sound signals into the fluid.The method according to the invention comprises emitting a reference sound signal with a reference sound frequency into the fluid by means of the sound transducer module, receiving a reference response signal by means of the sound transducer module, wherein the reference response signal is received in response to the emission of the reference sound signal, determining a signal quality of the reference response signal, determining an attenuation characteristic of the fluid on the basis of the determined signal quality of the reference response signal, adjusting the sound frequency of a measuring sound signal on the basis of the determined signal quality of the reference response signal and on the basis of the determined attenuation characteristic and controlling the sound transducer module such that the measuring sound signal with the adjusted sound frequency is emitted into the fluid for determining the height of the surface of the fluid and / or the quality of the fluid.The damping characteristics may depend in particular on the sound path length and / or the nature of the fluid.

[0014] The adjustment of the measuring sound frequency may in particular also depend on the signal-to-noise ratio of the response sound signal, which in turn depends on the attenuation characteristics of the sound path (i.e. the sound path length and the nature of the fluid).

[0015] In a preferred embodiment, adjusting the sound frequency of the measurement sound signal comprises reducing the measurement sound frequency if the determined signal quality of the reference response signal is less than a predetermined signal threshold. Alternatively or additionally, adjusting the sound frequency of the measurement sound signal comprises increasing the measurement sound frequency if the determined signal quality of the reference response signal is greater than the predetermined signal threshold.

[0016] It is preferable to continuously adjust the measurement sound frequency depending on the attenuation characteristics of the sound path. In particular, an already adjusted measurement sound frequency can serve as a reference sound frequency for further, subsequent adjustment of the sound frequency.

[0017] The method according to the invention preferably further comprises controlling the sound transducer module such that a first sound signal is emitted into the fluid at a first sound frequency when a first height of a first surface of the fluid is present, and controlling the sound transducer module such that a second sound signal is emitted into the fluid at a second sound frequency when a second height of a second surface of the fluid is present that is greater than the first height. Preferably, the first sound frequency is greater than the second sound frequency.

[0018] In a further preferred embodiment of the method according to the invention, the first sound frequency lies in a range between approximately 500 kHz and approximately 4 MHz. Furthermore, the second sound frequency lies in a range between approximately 100 kHz and approximately 2.5 MHz. Consequently, the sound signals are preferably ultrasonic signals.

[0019] Preferably, the method according to the invention further comprises determining the temperature of the fluid. The sound frequency is also adjusted based on the determined temperature. In particular, the temperature is an indicator of the viscosity of the fluid, which in turn can indicate the damping properties of the fluid or the nature of the fluid.

[0020] Advantageously, the fluid is engine oil, transmission oil, a urea solution, a fuel, or water. These fluids are preferably designed for use in a vehicle or an internal combustion engine of a vehicle.

[0021] According to a further aspect of the present invention, a fluid sensor device for determining the height of a surface of a fluid and / or a quality of the fluid in a fluid container is disclosed. The fluid sensor device according to the invention comprises at least one sound transducer module, which has a plurality of sound transducers provided in a matrix-like arrangement and is designed to emit and receive sound signals at different frequencies into the fluid, and a control unit designed to operate the fluid sensor device according to a method according to one of the preceding claims. In particular, the control unit is designed to control the at least one sound transducer module such that sound signals with an adapted sound frequency are emitted into the fluid. The sound frequency preferably decreases with increasing height of the surface of the fluid.

[0022] Thus, according to the invention, the frequency of the (measurement) sound signals is adjusted depending on the damping characteristics of the sound path. In particular, the frequency of the (measurement) sound signal should increase with decreasing damping characteristics. Conversely, the frequency of the (measurement) sound signal should decrease with increasing damping characteristics. For example, the frequency should be lower at high fill levels than at low fill levels due to the longer sound path. Furthermore, higher frequencies are preferable at high fluid temperatures than at lower temperatures, since the damping characteristics are higher at lower fluid temperatures than at higher fluid temperatures.

[0023] Further objects and features of the present invention will become apparent to those skilled in the art by practicing the present teachings and viewing the accompanying drawings in which: Fig. 1 shows a schematic view of a fluid sensor device according to the invention for determining a height of a surface of a fluid and / or a quality of the fluid in a fluid container, Fig. 2 shows a schematic view of another fluid sensor device according to the invention for determining a height of a surface of a fluid and / or a quality of the fluid in a fluid container, Fig. 3 shows a schematic view of yet another fluid sensor device according to the invention for determining a height of a surface of a fluid and / or a quality of the fluid in a fluid container, Fig. 4 shows an exemplary flow diagram of a method according to the invention for operating a fluid sensor device such that sound signals are emitted with a sound frequency adapted to the fill level of the fluid, Fig. 5 shows an exemplary flow diagram of another method for operating a fluid sensor device such that sound signals are emitted at a sound frequency adapted to the temperature of the fluid, and Fig. 6 shows an exemplary flow diagram of a further method for operating a fluid sensor device such that sound signals are emitted with a sound frequency adapted to the measuring task.

[0024] Elements of the same construction or function are provided with the same reference symbols throughout the figures.

[0025] In the context of the present disclosure, the term "fluid quality" describes a parameter that characterizes a fluid. For example, the speed of sound of the fluid, the density of the fluid, from which the chemical composition of the fluid can be derived, the electrical properties of the fluid, and the damping properties of the fluid can be considered parameters that characterize the fluid quality. For example, in an aqueous urea solution, such as urea, the urea content in the water can be estimated by determining the temperature-dependent speed of sound of the aqueous urea solution.

[0026] In the context of the present invention, the term “signal quality” describes, for example, the level of the amplitude, the signal-to-noise ratio, the shape of the signal envelope or the correlation between the transmitted signal and the received signal.

[0027] The Fig. 1 shows a fluid container 1 with a base section 3 and a fluid chamber 5 filled with a fluid F. The fluid F is, for example, a liquid medium for pollutant reduction in exhaust gases, which preferably contains a reducing agent and / or a reducing agent precursor, for example, an aqueous urea solution. Alternatively, the fluid F can be an oil, such as a transmission oil for a vehicle transmission. Furthermore, the fluid F can be an engine oil or a fuel.

[0028] For determining a height H1, H2 of a fluid surface O1, O2 in the fluid container 1, a fluid sensor device 100 is provided, which has a sound transducer module 10 arranged on the bottom section 3 of the fluid container 1. In the Fig. 1 shows two filling levels of the fluid F, namely a first height H1 of the surface O1 above the bottom section 3 and a second height of the surface O2 above the bottom section 3, which is greater than the first height H1.

[0029] In particular, as in the Fig. 1, the sound transducer module 10 can be arranged at a predetermined tilt angle α relative to the fluid surface O1, O2. For example, the base section 3 can have a corresponding recess 4 for this purpose, in which the sound transducer module 10 is attached to the outside of the fluid container 1. The fluid sensor device 10 further comprises a control unit 2 connected to the sound transducer module 10, which is designed to control the sound transducer module 10 to emit sound signals and to evaluate the signals received by the sound transducer module to determine the heights H1, H2 of the fluid surfaces O1, O2 and / or the quality of the fluid F.

[0030] The heights H1, H2 of the fluid surfaces O1, O2 are defined as the distances of the fluid surfaces O1, O2 from the bottom section 3, measured in a neutral position of the fluid container 1, i.e., when there is no inclination of the fluid container 1 and the fluid surfaces O1, O2 are essentially parallel to the bottom section 3. The heights H1, H2 of the fluid surfaces O1, O2 can also be referred to as the fill levels of the fluid F in the fluid container 1.

[0031] The sound transducer module 10 is coupled, for example, through a housing wall of the fluid container 1. For example, the housing wall is made of a plastic, such as high-density polyethylene (HDPE), so that the base section 3 can be welded into the housing wall. Alternatively, the sound transducer module 10 is glued to the housing wall or mechanically pressed against it, possibly also with an additional intermediate layer to compensate for unevenness or roughness.

[0032] The sound transducer module 10 comprises at least one sound transducer designed to transmit and receive sound signals. The sound transducer module 10 can be designed by different control to transmit a sound signal with different sound frequencies into the fluid F and to receive it again as a reflection signal. For example, in the Fig. 1 the sound signals emitted and received by the sound transducer module 10 are marked with arrows 12, 14, 16.

[0033] Furthermore, at least one reference element 8 is provided in the fluid F, which reference element is preferably made of a material comprising a metal. The reference element 8 reflects at least a portion of the sound signal 16 and is at a predetermined and constant distance from the sound transducer module 10. As shown in the Fig. 1, it may be preferred that the reference element 8 is mechanically coupled to the bottom section 3 within the fluid container 1.

[0034] The fluid sensor device 100 of the Fig. 1 also has a temperature detection device 9 designed to detect the temperature of the fluid. The temperature detection device 9 is, for example, a temperature sensor and is preferably arranged on the bottom section 3 of the fluid container 1.

[0035] The height H of the fluid surface O and / or the quality of the fluid is determined, as described in detail in the prior art, by evaluating the sound signals 12, 14 emitted to the fluid surfaces O1, O2, reflected at the fluid surfaces O1, O2 and received again, and by evaluating the sound signal 16 emitted to the reference element 8, reflected at the reference element 8 and received again, on the basis of which the quality of the fluid F, such as the speed of sound in the fluid F, can be determined.

[0036] As already mentioned, the sound transducer module 10 consists of several sound transducers arranged in a matrix-like configuration. Alternatively, any other arrangement of the multiple sound transducers is also conceivable, for example, a circular arrangement or an unsorted arrangement.

[0037] The plurality of sound transducers are preferably arranged in a common plane. In particular, the individual transmission points of the plurality of sound transducers are located in the common plane. Alternatively, the individual transmission points may not be arranged in a common plane, so that a desired sound signal can be generated by simultaneous and identical control of the plurality of sound transducers. In particular, by controlling the plurality of sound transducers with a time delay, the individual sound signals can be superimposed to form a superimposed sound signal, whereby the radiation direction of the superimposed sound signal relative to the common plane can be adjusted as desired.

[0038] Preferably, the plurality of sound transducers are arranged at a predetermined distance a from each other. The predetermined distance a between two adjacent sound transducers is preferably approximately an odd integer multiple (n) of half the wavelength λ of the sound signals emitted by the sound transducers, ie a=(2⋅n−1)⋅λ

[0039] The predetermined distance a is measured from the fictitious transmission point of one sound transducer to the fictitious transmission point of a neighboring sound transducer.

[0040] Each sound transducer is essentially identical and is preferably provided in the form of a capacitive micromechanical sound transducer (CMUT) or piezoelectric micromechanical sound transducer (PMUT). Each sound transducer emits a sound signal that is essentially perpendicular to the arrangement plane. Furthermore, it is preferred that each sound transducer emits sound signals that are essentially identical in terms of frequency and amplitude. The sound transducers are controlled jointly or separately, wherein the phase offset of the multiple sound signals can be adjusted by controlling the sound transducers at different times, thereby allowing the direction of the (superimposed) sound signal to be adjusted.

[0041] Alternatively, the multiple sound transducers can be configured differently and emit their respective sound signals in different directions. Preferably, however, the multiple sound transducers are each configured to emit a sound signal such that the multiple sound signals at least partially overlap to generate the superimposed sound signal.

[0042] In embodiments in which the sound transducer module 10 is arranged within the fluid container 1, e.g., attached from the inside to the bottom section 3 of the fluid container 1, it may be advantageous for each of the plurality of sound transducers to be assigned a sound guide element, each of which is designed to at least partially guide the respective sound signal of the assigned sound transducer. In particular, the respective sound guide element can be funnel-shaped, with the smaller opening assigned to the respective sound transducer. Alternatively, the sound guide element is cylindrical or has any other suitable shape.

[0043] The control unit 2 of the device according to the invention is designed to control the sound transducer module 10 such that a (superimposed) sound signal with an adjustable sound frequency is emitted into the fluid F, which signal propagates in a predetermined and desired direction. Due to their design, such sound transducers do not exhibit sharp resonance behavior and can thus be excited to emit sound waves with different sound frequencies over a wide frequency range by suitable control.

[0044] The total attenuation of the sound signals 12, 14 in the fluid F depends in particular on the attenuation of the sound path and the temperature-dependent viscosity of the fluid F. The attenuation of the sound path depends in particular on its length. More precisely, the longer the sound path, the higher the attenuation. This, in turn, means that the attenuation of the sound path increases with the height H1, H2 of the fluid surface O1, O2, since the travel distance of the sound signal increases with the height H1, H2 of the surface O1, O2 of the fluid F.

[0045] For this reason, it may be preferable to select a higher sound frequency for the sound signal emitted by the sound transducer module 10 into the fluid at the lower height H1 of the surface O1 of the fluid F than at the higher height H2 of the surface O2. By selecting a higher sound frequency at the lower height H2 of the surface O2 of the fluid F (i.e., at a lower fill level of the fluid F), the spatial resolution or measurement accuracy can be increased. Since the sound path through the fluid F is smaller than at higher fill levels, even with higher sound attenuation in the fluid F, the quality of the reflection signal can be sufficient to ensure reliable detection of the signal for the more critical low fill levels.

[0046] In contrast, it is preferable to select a lower sound frequency at the greater height H2 of surface O2 than at the lower height H1 of surface O1. This can at least partially ensure that a reflection signal of sufficient quality can be received despite the long travel distance through the fluid F and the associated greater attenuation. Although this may lower the spatial resolution or measurement accuracy at the greater height H2 of surface O2, the measurement accuracy requirements are generally lower at higher fill levels.

[0047] In addition to the attenuation of the sound signal due to the different travel distances through the fluid F, the attenuation caused by the strongly temperature-dependent viscosity of the fluid F must be taken into account according to the invention for sufficient measurement accuracy. For example, the attenuation increases with decreasing temperatures of the fluid F. Accordingly, according to the invention, the control unit 2 controls the sound transducer module 10 such that at low temperatures of the fluid F, a sound signal with a lower sound frequency is emitted into the fluid F than at high temperatures. This is particularly advantageous for fluids with generally high attenuation, such as engine oil or transmission oil, and for fluids with strongly temperature-dependent attenuation, such as diesel fuel.

[0048] While lowering the sound frequency can lead to reduced spatial resolution or measurement accuracy, receiving a usable reflection signal with lower spatial resolution is preferable to receiving a reflection signal that can no longer be analyzed at all. A reflection signal that can no longer be sufficiently analyzed occurs, for example, when the amplitude of the received reflection signal is so low that a reflection signal can no longer be distinguished from signal noise.

[0049] Accordingly, it may be preferable to select a higher sound frequency for the sound signal during quality measurement, in which the sound signals from the sound transducer module are transmitted to the reference element 8, than during level measurement, where the sound path is significantly longer than during quality measurement and where, due to unstable surfaces O1, O2, less favorable reflection conditions may exist than during quality measurement. This is because during quality measurement, the reference element 8 is preferably designed such that the sound signal arriving there is largely reflected back to the sound transducer module 10. In contrast, unstable surfaces O1, O2 lead to a strong scattering of the reflected sound signals, so that the portion reflected to the sound transducer module 10 is significantly lower than during quality measurement.

[0050] The Fig. 2 shows a further fluid sensor device 100 according to the invention, which has a first sound transducer module 10 and a second sound transducer module 11. Both sound transducer modules 10, 11 are controlled by the control unit 2, wherein the sound transducer module 10 is designed to emit the sound signals 12, 14 in the direction of the fluid surfaces O1, O2, and the sound transducer module 11 is designed to emit the sound signal 16 in the direction of the reference element 8. The sound transducer module 10 is thus oriented substantially horizontally and is preferably coupled from below to the bottom 3 of the fluid container 1 such that the sound signals 12, 14 are emitted in a vertical direction. The sound transducer module 11 is arranged substantially in a recess 4 in the bottom 3 of the fluid container 1 and is oriented substantially vertically, so that the sound signal 16 is emitted substantially horizontally.

[0051] As already mentioned in relation to the Fig. 1, in the fluid sensor device 100 of the Fig. 2, the sound signals 12, 14 are emitted by means of the sound transducer module 10 to determine the heights H1, H2 of the surfaces O1, O2 of the fluid F, wherein the sound signal 16 is emitted by means of the sound transducer module 11 to determine the quality of the fluid F. The sound transducer modules 10, 11 are controlled by means of the control unit 2.

[0052] The Fig. 3 shows yet another fluid sensor device 100 according to the invention. The fluid sensor device 100 of Fig. 3 differs from the fluid sensor device of the Fig. 1 in that the sound transducer module 10 is oriented substantially horizontally and is preferably attached from below to the base 3 of the fluid container 1. Furthermore, the reference element 8 is configured such that it reflects the vertically emitted sound signal 16 back to the sound transducer module 10. Thus, the sound transducer module 10 is designed to emit all sound signals 12, 14, 16 substantially in a vertical direction.

[0053] The Fig. 4 shows a flow diagram of a method according to the invention for adapting the sound frequency of the sound signal as a function of the attenuation of the sound signal due to the sound path length and / or due to the strongly temperature-dependent viscosity of the fluid F.

[0054] The procedure of Fig. 2 starts at step 200 and then proceeds to step 210, where the control unit 2 controls the sound transducer module 10 to emit a reference sound signal with a predetermined reference sound frequency into the fluid F in the direction of the fluid surface O1, O2. The reference sound frequency represents a starting sound frequency and can, for example, be in a range between approximately 1 MHz and 3 MHz.

[0055] In the subsequent step 220, a reference response signal is received from the sound transducer module 10. The reference response signal is received in response to the transmission of the reference sound signal. For example, the reference sound signal can be transmitted to the surface O1, O2 of the fluid F, reflected there, and received again as a reference response signal. Alternatively, it is possible to transmit the reference sound signal to the reference element 8, where it is reflected and received again as a reference response signal.

[0056] In the subsequent step 230, the signal quality of the reference response signal is determined. Determining the signal quality includes, for example, determining the amplitude of the reference response signal, determining an envelope of the response signal, or determining a correlation between the transmitted and received signals.

[0057] In the subsequent step 240, the sound frequency of the measurement sound signal emitted by the sound transducer module 10 is adjusted depending on the determined signal quality. For example, the sound frequency of the measurement sound signal is reduced if the signal quality is less than a predetermined signal threshold. Conversely, the sound frequency of the sound signal can be increased if the signal quality is greater than the predetermined signal threshold.

[0058] Following the adjustment of the sound frequency of the measuring sound signal, the sound transducer module 10 is controlled in step 250 such that the measuring sound signal with the adjusted sound frequency is emitted into the fluid F for level measurement and / or quality measurement before the method ends in step 260.

[0059] In particular, the Fig. 4, a method for operating a fluid sensor device 100 is provided, by means of which the different fill levels and / or the fluid quality can be detected as accurately as possible with adapted and different sound frequencies. For example, in the method of Fig. 2 advantageous to select a higher sound frequency for the measuring sound signal 12 at a low height H1 of the surface O1 than at the higher height H2 of the surface O2.

[0060] With reference to the Fig. 5 is a flowchart of an exemplary method for operating one of the fluid sensor devices 100 of the Fig. 1 to 3 shown.

[0061] The procedure of Fig. 5 starts at step 300 and then goes to step 310, in which the temperature of the fluid F is detected. For example, the control unit 2 can be designed to use the signal from the temperature sensor 9 (see Fig. 1 to 3) to determine the temperature of the fluid F.

[0062] In a subsequent step 320, a sound frequency for the sound signal to be emitted by the sound transducer module 10 is determined based on the detected temperature of the fluid F. For example, a sound frequency can be assigned to the detected temperature of the fluid F, preferably using a characteristic curve or a lookup table stored in the control unit 2. The characteristic curve and the lookup table assign a selectable sound frequency to each temperature of the fluid F. Furthermore, the sound frequency can be assigned using a mathematical mapping.

[0063] After determining the sound frequency in step 320, in the following step 330 the sound transducer module 10 is controlled by the control unit 2 such that the sound transducer module 10 emits a sound signal with the sound frequency determined in step 320 into the fluid F. The method of Fig. 5 ends at step 340.

[0064] Taking into account the Fig. 4, the control unit 2 can consequently be configured to control the sound transducer module 10 such that the sound transducer module 10 emits a sound signal with a sound frequency that is optimized with regard to the prevailing fill level and the temperature of the fluid F. This means that the damping characteristic, which depends on the sound path length and the viscosity of the fluid, is taken into account and thus improved measurement accuracy can be achieved when detecting the fill level and / or the quality of the fluid F, or the measurement can be carried out reliably over a wider temperature range.

[0065] Furthermore, it may be advantageous to select and adapt the sound frequency depending on the measuring task. For example, it may be preferable to select a lower sound frequency when measuring the heights H1, H2 of the surfaces O1, O2 of the fluid F than when measuring the quality of the fluid F. When transmitting the sound signal to the reference element 8 for quality measurement, a high spatial resolution or high measurement quality may be desired so that the quality of the fluid F, such as the speed of sound in the fluid F, can be determined as accurately as possible. The speed of sound determined in this way is then also used to determine the heights H1, H2 of the surfaces O1, O2 of the fluid F, which is why the speed of sound should preferably be determined with high accuracy. Furthermore, the distance traveled by the heterodyne sound signal through the fluid F is usually shorter in this quality measurement than in the fill level measurement.

[0066] The Fig. 6 shows a further flowchart of another exemplary method for operating one of the fluid sensor devices 100 of the Fig. 1 to 3, in which the sound frequency is adjusted depending on the measurement task.

[0067] The procedure of Fig. 6 starts at step 400 and then proceeds to step 410, where the measurement task is determined. For example, step 410 can determine whether a level measurement or a quality measurement should be performed.

[0068] If it is determined in step 410 that a fill level measurement should be performed, the method proceeds to step 420, in which, based on the determined fill level measurement, a first sound frequency is determined for the first sound signal to be emitted by the sound transducer module 10. In the subsequent step 430, a first sound signal with the determined first sound frequency is emitted in the direction of the surface O1, O2 to determine the height H1, H2 of the surface O1, O2 of the fluid F, and the fill level of the fluid F in the fluid container 1 is determined from the response signal reflected at the surface O1, O2 before the method ends in step 460.

[0069] However, if it is determined in step 410 that a quality measurement should be performed, the method proceeds to step 440, in which, based on the determined quality measurement, a second sound frequency is determined for the second sound signal to be emitted by the sound transducer module 10. In the subsequent step 450, the second sound signal is emitted at the determined second sound frequency in the direction of the reference element 8, and the quality of the fluid F is determined from the response signal reflected at the reference element 8, before the method again ends in step 460. In particular, this can be used to determine the speed of sound in the fluid F, which can indicate the quality of the fluid and can also be used for level measurement.

[0070] In the process of Fig. 6, for example, it can be used to advantage that, due to the longer signal path, a lower frequency may be advantageous for level measurement than for quality measurement, which has a comparatively shorter signal path. Furthermore, increased spatial resolution or measurement accuracy may be required for quality measurement, so a higher sound frequency for the sound signal is preferable.

[0071] Taking into account the Fig. 4 to 6, the control unit 2 can consequently be designed to control the sound transducer module 10 such that the sound transducer module 10 emits a sound signal with a sound frequency that is optimized with regard to the prevailing fill level, the temperature of the fluid F and the measurement task. This means that the damping characteristic, which depends on the sound path length and the viscosity of the fluid, is taken into account in both the fill level and quality measurement and thus an improved measurement accuracy can be achieved in the detection of the fill level and / or the quality of the fluid F or the measurement can be reliably carried out in a wider temperature range. Thus, the Fig. 4 to 6 for adjusting the frequency of the sound signals emitted by the sound transducer module 10, 11 can be combined with one another in order to achieve optimal adaptation of the measuring process to the given conditions.

Claims

[1] Method for operating a fluid sensor device (100) which is designed to determine the height (H) of a surface (O) of a fluid (F) and / or a quality of the fluid (F) in a fluid container (1) by means of at least one sound transducer module (10) which has a plurality of sound transducers provided in a matrix-like arrangement and is designed to emit and receive sound signals into the fluid (F), the method comprising: - emitting a reference sound signal with a reference sound frequency into the fluid (F) by means of the sound transducer module (10), - receiving a reference response signal by means of the sound transducer module (10), wherein the reference response signal is received in response to the transmission of the reference sound signal, - Determining the signal quality of the reference response signal, - determining a damping characteristic of the fluid (F) on the basis of the determined signal quality of the reference response signal, - Adjusting a sound frequency of a measuring sound signal based on the determined signal quality of the reference response signal and on the basis of the determined attenuation characteristic, and - controlling the sound transducer module (10) such that the measuring sound signal with the adapted sound frequency is emitted into the fluid (F) for determining the height (H) of the surface (O) of the fluid (F) and / or the quality of the fluid (F). [2] The method of claim 1, wherein adjusting the sound frequency of the measuring sound signal comprises: - reducing the measuring sound frequency if the determined signal quality of the reference response signal is less than a predetermined signal threshold, and - Increasing the measuring sound frequency if the determined signal quality of the reference response signal is greater than the predetermined signal threshold. [3] The method of claim 1 or 2, further comprising: - controlling the sound transducer module (10) such that a first sound signal with a first sound frequency is emitted into the fluid (F) when a first height (H1) of a first surface (O1) of the fluid is present, and - controlling the sound transducer module (10) such that a second sound signal with a second sound frequency is emitted into the fluid (F) when a second height (H2) of a second surface (O2) of the fluid is present which is greater than the first height (H1). [4] The method of claim 3, wherein the first sound frequency is greater than the second sound frequency. [5] Method according to one of claims 3 and 4, wherein the first sound frequency is in a range between approximately 500 kHz and approximately 4 MHz, and wherein the second sound frequency is in a range between approximately 100 kHz and approximately 2.5 MHz. [6] A method according to any one of claims 3 to 5, further comprising: - Determining a temperature of the fluid (F), wherein the adjustment of the sound frequency is further carried out on the basis of the determined temperature. [7] Method according to one of the preceding claims, wherein the fluid is engine oil, gear oil, a urea solution, a fuel or water. [8] Fluid sensor device (100) for determining the height (H) of a surface (O) of a fluid (F) and / or a quality of the fluid (F) in a fluid container (B), the fluid sensor device (100) comprising: - at least one sound transducer module (10) which has a plurality of sound transducers provided in a matrix-like arrangement and is designed to emit and receive sound signals with different frequencies into the fluid (F), and - a control unit (2) which is designed to operate the fluid sensor device (100) according to a method according to one of the preceding claims. [9] Fluid sensor device (100) according to claim 8, wherein the sound frequency decreases with increasing height (H1, H2) of the surface (O1, O2) of the fluid (F).

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