Method for combined pressure-sound measurement and pressure-sound sensor

Abstract

The invention relates to a method for combined pressure-sound measurement (52) of ambient pressure (p) acting on a pressure-sound sensor (10) from a sensor environment (12) and sound vibrations (14) acting from the sensor environment (12), comprising the steps of providing (54) the pressure-sound sensor (10) with a capacitive measuring device (16) which influences an electrical voltage signal (60) depending on a deflection of a deflection element (18) and which comprises an electrode arrangement (20) with at least one counter electrode (22) and at least one electrode (36, 38) on the deflection element (18) which is deflectable relative to the counter electrode (22), applying an electrical basic voltage (U) to the electrode arrangement (20), detecting (58) a voltage signal (60) containing a dynamic component (62) depending on the sound vibrations (14) at the electrode arrangement (20), Determining the sound vibrations (14) depending on the dynamic component (62),wherein an electrical modulation voltage signal (70) is superimposed on the base voltage (U) at least temporarily, the modulation voltage signal (70) generates a modulation voltage response (72) in the voltage signal (60) as a function of the ambient pressure (p), and the ambient pressure (p) is determined at least as a function of the modulation voltage response (72). Furthermore, the invention relates to a pressure-sound sensor (10).

Description

The invention relates to a method for combined pressure-sound measurement according to the preamble of claim 1.Prior ArtIn the measurement of sound, microelectromechanical (MEMS) microphones have proven to be space-saving and efficient. These MEMS microphones typically use a sensitive diaphragm which deflects depending on acoustic pressure waves and influences electrical voltage signals depending on the deflection.In particular in capacitive MEMS microphones, in which an electrode arrangement comprising a movable electrode and a counter electrode is used, the application of a basic electrical voltage to the electrode arrangement and the resulting change in capacitance between electrode and counter electrode by deflection of the movable electrode enables a conversion of sound acting into electrical voltage signals.DE 10 2015 103 236 A1 describes a pressure-sound sensor which is configured with its double-layer electrode structure for measuring both an applied pressure and an applied sound.Disclosure of the InventionAccording to the present invention, there is provided a method of combined pressure-sound measurement having the features of claim 1. As a result, with a single MEMS component, here the pressure-sound sensor, both the ambient pressure and sound oscillations, i.e. acoustic oscillations, can be measured. The ambient pressure and the sound oscillations can be measured using measurement principles that are independent of one another.The pressure-sound sensor can be a microelectromechanical pressure-sound sensor. The pressure-sound sensor can be a capacitive microphone, preferably a MEMS microphone, with which a measurement of the ambient pressure is also implemented. The pressure-sound sensor can measure the pressure as absolute pressure and / or differential pressure.The pressure-sound sensor can be installed in a vehicle, an aircraft, a watercraft, an industrial product and / or a consumer product. The consumer product can be a mobile device, in particular a smartphone or a wearable, preferably a smart watch.The ambient pressure is a pressure of an ambient medium of the sensor environment. The surrounding medium is a fluid, preferably air or a liquid. The ambient pressure is a fluid pressure, preferably an air pressure, in particular an atmospheric pressure, or a liquid pressure, for example a water pressure.The ambient pressure acting on the pressure-sound sensor and the sound oscillations acting are introduced in particular by one and the same ambient medium.The deflection element can have at least one deflectable deflection component, preferably at least two deflectable deflection components. An electrode can be assigned to the deflection component, preferably each of the deflection components. The deflection component can be a membrane. The electrode may be attached to the deflection member. The electrode and the deflection component can be embodied in one piece or in one piece. The deflection component itself can form the electrode.At least two deflection members may be spaced apart from each other in an axial direction and define a space therebetween. The space may be sealed from the sensor environment. The intermediate space can be filled with a gas. A pressure in the intermediate space can be less than the smallest ambient pressure to be measured.At least one connecting opening can connect the one side of the one deflection component facing away from the intermediate space and facing the sensor environment and the other side of the other deflection component facing away from the intermediate space to one another in a pressure-compensating manner. As a result, the measurement of the sound oscillations can be carried out independently of the ambient pressure. A connection between the connecting opening and the intermediate space can be omitted. The connecting opening can be arranged in a center of the deflection element.The counter electrode can be arranged between the two deflection components.A differential measurement can thereby be carried out. The two deflection components can be connected to one another in the axial direction by connecting means for transmitting a deflection of the one deflection element to the other deflection element. The counter electrode can have through-openings, in particular for the passage of the connecting means and / or for the reduction of damping. The connecting means can comprise webs, columns and / or springs. Each connecting means can be assigned a single through-openings. A plurality of connecting means can also be arranged in a through-opening. The through-opening can have any desired shape, in particular circular.The electrode arrangement can be applied to a carrier element, in particular a substrate. The carrier element can have a recess into which the deflection element, preferably at least one deflection component of the deflection element, can deflect in the axial direction.The deflection of the deflection element can influence the electrical capacitance between at least one of the electrodes and the counter electrode.The basic electrical voltage can be a direct electrical voltage.The modulation voltage signal can be superimposed in time segments which in turn are alternated with time segments in which no modulation voltage signal is present.The modulation voltage response may be an amplitude spectrum and / or phase spectrum over frequency, respectively.In a preferred embodiment of the invention, it is advantageous if at least the amplitudes of the modulation voltage response are evaluated in order to determine the ambient pressure as a function of the modulation voltage response. Furthermore, amplitudes of the modulation voltage signal can be evaluated. The amplitudes of the modulation voltage response can be normalized with the amplitudes of the modulation voltage signal. The electrical frequency at a maximum amplitude of the modulation voltage response, preferably at a maximum normalized amplitude, can be determined and assumed to correspond to the mechanical resonant frequency of the deflection element. The ambient pressure assigned to the resonant frequency can be calculated by a previously known pressure-resonant relationship depending on the determined resonant frequency, optionally taking into account the temperature. The ambient pressure can thus be determined from the amplitude maximum.In a further specific embodiment of the invention, it is advantageous if at least the phases of the modulation voltage response are evaluated in order to determine the ambient pressure as a function of the modulation voltage response. The electrical phase of the modulation voltage response at the resonant frequency may preferably be determined in advance. The electrical frequency corresponding to the mechanical resonant frequency of the deflection element can then be determined from the modulation voltage response by the phase position. This determination is extremely power-saving and quick.In an advantageous embodiment of the invention, it is provided that the mechanical resonant frequency of the deflection element or of at least one deflection component of the deflection element is variable as a function of the ambient pressure and the modulation voltage signal has an electrical modulation frequency range which includes frequencies corresponding at least to the expected pressure-dependent resonant frequencies of the deflection element or of the deflection component. The mechanical resonant frequency can correspond to the natural frequency of the deflection element or of the deflection component or to a multiple of the natural frequency of the deflection element or of the deflection component.In an advantageous embodiment of the invention, it is provided that the modulation frequency range excludes the electrical frequencies corresponding to a mechanical resonant frequency of the counter electrode. The modulation frequency range may be outside the electrical frequencies corresponding to the mechanical resonant frequencies of the counter electrode. An upper frequency value of the modulation frequency range may be smaller than the electrical frequency corresponding to a mechanical resonance frequency of the counter electrode. A lower frequency value of the modulation frequency range may be greater than the electrical frequency corresponding to a mechanical resonant frequency of the counter electrode.In a preferred embodiment of the invention, it is advantageous if the electrical frequency is determined at a maximum amplitude of the modulation voltage response and is assumed to be the mechanical resonant frequency of the deflection element or of the deflection component.In a preferred embodiment of the invention, it is advantageous if the ambient pressure assigned to the resonant frequency is calculated by a previously known pressure-resonant relationship as a function of the determined resonant frequency. The pressure-resonance relationship can be specified analytically or numerically, preferably via a look-up table, and can be stored in a memory unit, in particular in an ASIC.In a special embodiment of the invention, it is advantageous if the acoustic vibrations are measured in a predetermined acoustic frequency range, which corresponds to a dynamic frequency range of the dynamic component, wherein the modulation frequency range lies outside the dynamic frequency range. As a result, the ambient pressure and the sound oscillations can be measured simultaneously and independently of one another. The modulation frequency range can have a lower frequency greater than the greatest frequency of the dynamic frequency range as the frequency of the sound oscillations to be measured, preferably 20 kHz.In a special embodiment of the invention, it is advantageous if the modulation voltage signal is a time frequency sweep or a simultaneous broadband frequency superposition. The frequency superposition can be an electrical voltage pulse.In a special embodiment of the invention, it is advantageous if the frequency sweep takes place at least over the modulation frequency range or the frequency superposition has at least the modulation frequency range. During the frequency sweep, the frequencies of the modulation frequency range can be traversed successively in time. The frequency superposition may simultaneously superimpose the frequencies of the modulation frequency range.According to the present invention, there is further provided a pressure-sound sensor having the features of claim 10. As a result, the combined pressure-sound measurement can be carried out as compactly and cost-effectively as possible.Further advantages and advantageous embodiments of the invention result from the description of the figures and the figures.DESCRIPTION OF THE FIGURESThe invention will be described in detail below with reference to the drawings. They show in detail: FIG. 1 : A pressure-sound sensor in a specific embodiment of the invention. FIG. 2 : A method for combined pressure-sound measurement in a specific embodiment of the invention. FIG. 3 : shows a pressure-sound sensor during a measurement of the ambient pressure in the method from FIG. 2.Figure 1 shows a pressure-sound sensor in a specific embodiment of the invention. The pressure-sound sensor 10 for the pressure-sound measurement of ambient pressure p acting from a sensor environment 12 and sound oscillations 14 acting from the sensor environment 12 comprises a capacitive measuring device 16, which influences an electrical voltage signal depending on a deflection of a deflection element 18 and which comprises an electrode arrangement 20.The electrode arrangement 20 comprises a rigid counter electrode 22, preferably a back plate, and the deflection element 18 deflectable with respect thereto, having a first deflection component 24 and a second deflection component 28 spaced apart therefrom in an axial direction 26. The intermediate space 30 is designed as a cavity which is sealed with respect to the sensor environment 12. A gas can be accommodated in the interspace 30. A pressure in the intermediate space 30 can be less than the smallest ambient pressure p to be measured.The one side of the first deflection component 24 facing the sensor environment 12 and the other side of the second deflection component 28 facing away from the intermediate space 30 are connected to one another in a pressure-compensating manner via a central connecting opening 32. As a result, the measurement of the sound oscillations 14 can be carried out more independently of the ambient pressure p. The communication hole 32 is separated from the clearance 30.The first deflection component 24 is embodied as a diaphragm 34 and forms a first electrode 36 and the second deflection component 28 is embodied as a diaphragm 34 and forms a second electrode 38. As a result, a capacitive differential measurement can be carried out.The first and second deflection components 24, 28 are connected to one another in the axial direction 26 by connecting means 40, preferably webs, columns and / or springs, for transmitting a deflection of the first deflection component 24 to the second deflection component 28. The counter electrode 22 has through-openings 42 for the passage of the connecting means 40. Each connecting means 40 is assigned in particular an individual through-openings 42 in the counter electrode 22.The electrode arrangement 20 is applied to a carrier element 44, in particular a substrate 46. The carrier element 44 comprises a recess 48, into which the second deflection component 28 can deflect in the axial direction 26.The ambient pressure p acting on the pressure-sound sensor 10 and the acting sound oscillations 14 are introduced onto the electrode arrangement 20 by one and the same ambient medium 50, for example air.FIG. 2 shows a method for combined pressure-sound measurement in a specific embodiment of the invention. The method for combined pressure-sound measurement 52 of an ambient pressure p acting on a pressure-sound sensor 10 from a sensor environment 12 and sound oscillations 14 acting from the sensor environment 12 comprises first of all providing 54 the pressure-sound sensor 10 described, for example, in FIG. 1.An electrical supply of the electrode arrangement 20 is effected by applying an electrical base voltage U to the electrode arrangement 20, the base voltage being present between, on the one hand, the counter electrode 22 and, on the other hand, the first electrode 36 and the second electrode 38. The first and second electrodes 36, 38 are thus electrically connected in parallel.The sound vibrations 14 acting on the electrode arrangement 20 are measured by detecting 58 a voltage signal 60 at the electrode arrangement 20. The voltage signal 60 contains a dynamic component 62 depending on the sound oscillations 14. the sound oscillations 14 are measured in a predefined acoustic frequency range, which preferably corresponds to a dynamic frequency range of the dynamic component.The acoustic oscillations 14 are determined differentially by detecting and evaluating 64 the dynamic frequency range of the dynamic component 62, in that an amplified first voltage signal 66 of the first electrode 36 and an amplified second voltage signal 68 of the second electrode 38 are compared with one another.To measure the pressure of the ambient pressure p independently of the sound measurement of the sound oscillations 14, an electrical modulation voltage signal 70 is superimposed on the basic voltage U, which modulation voltage signal generates a modulation voltage response 72 in the voltage signal 60 as a function of the ambient pressure p. In this case, the fact is used that the mechanical resonant frequency fr of the deflection components 24, 28 is variable as a function of the ambient pressure p.The ambient pressure p is then determined at least as a function of the modulation voltage response 72, in that the amplitudes of the modulation voltage response 72 are evaluated. Furthermore, amplitudes A' of the modulation voltage signal 70 can be evaluated. The amplitudes of the modulation voltage response 72 may be normalized with the amplitudes A' of the modulation voltage signal 70 and may be indicated as normalized amplitudes A. The electrical frequency at a maximum normalized amplitude A of the modulation voltage response can be determined and assumed to correspond to the mechanical resonant frequency fr of the deflection component 24, 28. The ambient pressure p assigned to the resonant frequency fr can be calculated by a previously known pressure-resonance relationship 76 depending on the determined resonant frequency fr, optionally taking into account the temperature. The ambient pressure p can thus be determined from the amplitude maximum of the normalized amplitudes A.The modulation voltage signal 70 includes an electrical modulation frequency range 78, which includes at least the frequencies corresponding to the expected pressure-dependent resonant frequencies fr of the deflection components 24, 28 and which lies outside the dynamic frequency range. Preferably, the modulation frequency range 78 further excludes the electrical frequencies corresponding to a mechanical resonant frequency of the counter electrode 22 to prevent self-oscillation of the suspended counter electrode 22.The modulation voltage signal 70 is embodied as a temporal frequency sweep 80 or a simultaneous broadband frequency superposition. The frequency sweep 80 is preferably effected at least over the modulation frequency range 78 or the frequency superposition has at least the modulation frequency range 78.Alternatively to the embodiment described above, the deflection element 18 can be embodied without the first deflection component 24 and the first electrode 36 and can have only the second deflection component 28 and thus the second electrode 38. The sound oscillations 14 are determined by detecting and evaluating 64 the dynamic frequency range of the dynamic component 62 exclusively of the amplified second voltage signal 68 of the second electrode 38.FIG. 3 shows a pressure-sound sensor during a measurement of the ambient pressure in the method from FIG. 2 The pressure-sound sensor 10 is depicted during a measurement of the ambient pressure p, in which the modulation voltage signal mechanically excites the deflection components 24, 28 of the deflection element 18 and in the process brings about the oscillation 82 taking place at the resonant frequency. The resonant frequency of the oscillation 82 is dependent on a mechanical stress in the deflection components 24, 28. The resonant frequency can be structurally influenced, for example, by selection of the connecting means 40, for example a distance of the connecting means 40, a number of the connecting means 40 and / or by the thickness of the first and second deflection components 24, 28, in particular in order to set an offset between the resonant frequency and the dynamic frequency range.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2015 103 236 A1

[0004]

Claims

Method for combined pressure-sound measurement (52) of ambient pressure (p) acting on a pressure-sound sensor (10) from a sensor environment (12) and sound oscillations (14) acting from the sensor environment (12), comprising the steps of providing (54) the pressure-sound sensor (10) with a capacitive measuring device (16) which influences an electrical voltage signal (60) as a function of a deflection of a deflection element (18) and which comprises an electrode arrangement (20) with at least one counter electrode (22) and at least one electrode (36, 38) on the deflection element (18) deflectable with respect to the counter electrode (22), applying an electrical basic voltage (U) to the electrode arrangement (20), detecting (58) on the electrode arrangement (20) a voltage signal (60) containing a dynamic component (62) as a function of the sound oscillations (14), Determination of the acoustic oscillations (14) as a function of the dynamic component (62), characterized in that an electrical modulation voltage signal (70) is superimposed at least temporarily on the base voltage (U), the modulation voltage signal (70) generates a modulation voltage response (72) in the voltage signal (60) as a function of the ambient pressure (p), and the ambient pressure (p) is determined at least as a function of the modulation voltage response (72).Method for combined pressure-sound measurement (52) according to Claim 1, characterized in that at least the amplitudes and / or phases of the modulation voltage response (72) are evaluated in order to determine the ambient pressure (p) as a function of the modulation voltage response (72).Method for combined pressure-sound measurement (52) according to Claim 1 or 2, characterized in that the mechanical resonant frequency (fr) of the deflection element (18) or, if appropriate, of at least one deflection component (24, 28) of the deflection element (18) is variable as a function of the ambient pressure (p), and the modulation voltage signal (70) has an electrical modulation frequency range (78) which includes frequencies (f) corresponding at least to the expected pressure-dependent resonant frequencies (fr) of the deflection element (18) or of the deflection component (24, 28).Method for combined pressure-sound measurement (52) according to Claim 3, characterized in that the modulation frequency range (78) excludes the electrical frequency corresponding to a mechanical resonant frequency of the counter electrode (22).Method for combined pressure-sound measurement (52) according to Claim 2 and Claim 3 or 4, characterized in that the electrical frequency (f) is determined at a maximum amplitude (A) of the modulation voltage response (72) and is assumed as the mechanical resonant frequency (fr) of the deflection element (18) or of the deflection component (24, 28).Method for combined pressure-sound measurement (52) according to Claim 5, characterized in that the ambient pressure (p) assigned to the resonant frequency (fr) is calculated by a previously known pressure-resonance relationship (76) as a function of the determined resonant frequency (fr).Method for combined pressure-sound measurement (52) according to one of Claims 3 to 6, characterized in that the sound oscillations (14) are measured in a predefined acoustic frequency range which corresponds to a dynamic frequency range of the dynamic component, the modulation frequency range (78) lying outside the dynamic frequency range.Method for combined pressure-sound measurement (52) according to one of the preceding claims, characterized in that the modulation voltage signal (70) is a time-based frequency sweep (80) or a simultaneous broadband frequency superposition.Method for combined pressure-sound measurement (52) according to one of Claims 3 to 7 and Claim 8, characterized in that the frequency sweep (80) takes place at least over the modulation frequency range (78) or the frequency superposition has at least the modulation frequency range (78).Pressure-sound sensor (10) comprising a capacitive measuring device (16) which influences an electrical voltage signal (60) as a function of a deflection of a deflection element (18) and which comprises an electrode arrangement (20) having at least one counter electrode (22) and at least one electrode (36, 38) on the deflection element (18) deflectable with respect to the counter electrode (22) and which is configured to determine an ambient pressure (p) acting from a sensor environment (12) and sound oscillations (14) acting from the sensor environment (12) with a method for combined pressure-sound measurement (52) according to one of the preceding claims.

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