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 thereon from the sensor environment (12), having the steps of providing (54) the pressure / sound sensor (10) having a capacitive measuring device (16) which influences an electric 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 can be deflected with respect to the counter electrode (22), applying a fundamental voltage (U) to the electrode arrangement (20), sensing a voltage signal (60), containing a dynamic portion (62) depending on the sound vibrations (14), at the electrode arrangement (20), determining the sound vibrations (14) depending on the dynamic portion (62), wherein an electric modulation voltage signal (70) is at least temporarily superimposed on the fundamental voltage (U), the modulation voltage signal (7) generates a modulation voltage response (72) in the voltage signal (60) depending on the ambient pressure (p), and the ambient pressure (p) is determined at least depending on the modulation voltage response (72). The invention also relates to a pressure / sound sensor (10).

Description

[0001] Description

[0002] title

[0003] Method for combined pressure-sound measurement and pressure-sound sensor

[0004] The invention relates to a method for combined pressure-sound measurement according to the preamble of claim 1. Furthermore, the invention relates to a pressure-sound sensor.

[0005] State of the art

[0006] Microelectromechanical (MEMS) microphones have proven to be space-saving and efficient for measuring sound. These MEMS microphones typically use a sensitive membrane that deflects in response to acoustic pressure waves and influences electrical voltage signals depending on the deflection.

[0007] Particularly in capacitive MEMS microphones, which use an electrode arrangement consisting of a movable electrode and a counter electrode, 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 the conversion of incoming sound into electrical voltage signals.

[0008] DE 10 2015 103 236 A1 describes a pressure-sound sensor which, with its double-layer electrode structure, is designed to measure both an applied pressure and an acting sound.

[0009] Disclosure of the invention

[0010] According to the present invention, a method for combined pressure-sound measurement is proposed with the features of claim 1. This allows both ambient pressure and sound vibrations, i.e., acoustic vibrations, to be measured using a single MEMS component, in this case the pressure-sound sensor. The ambient pressure and sound vibrations can be measured using independent measurement principles.

[0011] The pressure-sound sensor can be a microelectromechanical pressure-sound sensor. The pressure-sound sensor can be a capacitive microphone, preferably a MEMS microphone, which also measures the ambient pressure. The pressure-sound sensor can measure pressure as absolute pressure and / or differential pressure.

[0012] 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 smartwatch.

[0013] The ambient pressure is the pressure of an ambient medium in the sensor environment. The ambient medium is a fluid, preferably air or a liquid. The ambient pressure is a fluid pressure, preferably air pressure, in particular atmospheric pressure, or a liquid pressure, for example, water pressure.

[0014] The ambient pressure acting on the pressure-sound sensor and the acting sound vibrations are introduced in particular by one and the same ambient medium.

[0015] The deflection element can have at least one deflectable deflection component, preferably at least two deflectable deflection components. An electrode can be associated with the deflection component, preferably with each of the deflection components. The deflection component can be a membrane. The electrode can be attached to the deflection component. The electrode and the deflection component can be designed as a single piece or in one piece. The deflection component itself can form the electrode.

[0016] At least two deflection components can be spaced apart in an axial direction, spanning a gap between them. The gap can be sealed from the sensor environment. The gap can be filled with a gas. The pressure in the gap can be less than the lowest ambient pressure to be measured.

[0017] At least one connecting opening can connect the side of one deflection component facing away from the gap and toward the sensor environment to the other side of the other deflection component facing away from the gap in a pressure-equalizing manner. This allows the sound vibrations to be measured independently of the ambient pressure. A connection between the connecting opening and the gap can be omitted. The connecting opening can be located at a center of the deflection element.

[0018] The counter electrode can be arranged between the two deflection components. This allows a differential measurement to be performed. The two deflection components can be connected to one another in the axial direction by connecting means for transmitting a deflection of one deflection element to the other deflection element. The counter electrode can have through-openings, in particular for passing through the connecting means and / or for reducing damping. The connecting means can comprise webs, columns, and / or springs. Each connecting means can be assigned a single through-opening. Multiple connecting means can also be arranged in one through-opening. The through-opening can have any shape, in particular circular.

[0019] 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.

[0020] The deflection of the deflection element can influence the electrical capacitance between at least one of the electrodes and the counter electrode.

[0021] The basic electrical voltage can be a direct electrical voltage.

[0022] The modulation voltage signal can be superimposed in time periods which in turn are alternated by time periods in which no modulation voltage signal is present.

[0023] The modulation voltage response can be an amplitude spectrum and / or phase spectrum, each over the frequency.

[0024] In a preferred embodiment of the invention, it is advantageous if, to determine the ambient pressure, at least the amplitudes of the modulation voltage response are evaluated depending on 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 resonance frequency of the deflection element. The ambient pressure associated with the resonance frequency can be calculated using a previously known pressure-resonance relationship depending on the determined resonance frequency, optionally taking temperature into account. The ambient pressure can thus be determined from the amplitude maximum.

[0025] In a further specific embodiment of the invention, it is advantageous if, to determine the ambient pressure, at least the phases of the modulation voltage response are evaluated depending on the modulation voltage response. The electrical phase of the modulation voltage response at the resonant frequency can 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 using the phase angle. This determination is extremely power-efficient and fast.

[0026] In an advantageous embodiment of the invention, the mechanical resonance frequency of the deflection element or at least one deflection component of the deflection element is variable depending on the ambient pressure, and the modulation voltage signal has an electrical modulation frequency range that includes frequencies corresponding at least to the expected pressure-dependent resonance frequencies of the deflection element or the deflection component. The mechanical resonance frequency can correspond to the natural frequency of the deflection element or the deflection component or to a multiple of the natural frequency of the deflection element or the deflection component.

[0027] In an advantageous embodiment of the invention, the modulation frequency range excludes the electrical frequencies corresponding to a mechanical resonance frequency of the counterelectrode. The modulation frequency range can be outside the electrical frequencies corresponding to the mechanical resonance frequencies of the counterelectrode. An upper frequency value of the modulation frequency range can be lower than the electrical frequency corresponding to a mechanical resonance frequency of the counterelectrode. A lower frequency value of the modulation frequency range can be higher than the electrical frequency corresponding to a mechanical resonance frequency of the counterelectrode.

[0028] 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 resonance frequency of the deflection element or the deflection component.

[0029] In a preferred embodiment of the invention, it is advantageous if the ambient pressure associated with the resonance frequency is calculated using a previously known pressure-resonance relationship as a function of the determined resonance frequency. The pressure-resonance relationship can be specified analytically or numerically, preferably via a lookup table, and stored in a memory unit, in particular in an ASIC.

[0030] In a specific embodiment of the invention, it is advantageous if the sound vibrations are measured in a predetermined acoustic frequency range corresponding to a dynamic frequency range of the dynamic component, with the modulation frequency range lying outside the dynamic frequency range. This allows the ambient pressure and the sound vibrations to be measured simultaneously and independently of one another. The modulation frequency range can have a lower frequency greater than the highest frequency of the dynamic frequency range as the frequency of the sound vibrations to be measured, preferably 20 kHz.

[0031] In a specific embodiment of the invention, it is advantageous if the modulation voltage signal is a temporal frequency sweep or a simultaneous broadband frequency superposition. The frequency superposition can be an electrical voltage pulse.

[0032] In a specific embodiment of the invention, it is advantageous if the frequency sweep occurs at least over the modulation frequency range or if the frequency superposition comprises at least the modulation frequency range. During the frequency sweep, the frequencies of the modulation frequency range can be traversed one after the other. The frequency superposition can superimpose the frequencies of the modulation frequency range simultaneously.

[0033] According to the present invention, a pressure-sound sensor with the features of claim 10 is further proposed. This allows the combined pressure-sound measurement to be carried out as compactly and cost-effectively as possible.

[0034] Further advantages and advantageous embodiments of the invention emerge from the description of the figures and the illustrations.

[0035] Description of the Figures The invention is described in detail below with reference to the figures. They show in detail:

[0036] Figure 1: A pressure-sound sensor in a special embodiment of the invention.

[0037] Figure 2: A method for combined pressure-sound measurement in a special embodiment of the invention.

[0038] Figure 3: A pressure-sound sensor measuring the ambient pressure using the method of Figure 2.

[0039] Figure 1 shows a pressure-sound sensor in a specific embodiment of the invention. The pressure-sound sensor 10 for measuring the ambient pressure p acting from a sensor environment 12 and the sound vibrations 14 acting from the sensor environment 12 comprises a capacitive measuring device 16, which influences an electrical voltage signal depending on the deflection of a deflection element 18 and which comprises an electrode arrangement 20.

[0040] The electrode arrangement 20 comprises a rigid counterelectrode 22, preferably a backplate, and the deflection element 18, which can be deflected relative to the counterelectrode, having a first deflection component 24 and a second deflection component 28 spaced therefrom in an axial direction 26. The counterelectrode 22 is arranged in a space 30 spanned between the first and second deflection components 24, 28. The space 30 is designed as a cavity that is sealed from the sensor environment 12. A gas can be accommodated in the space 30. A pressure in the space 30 can be less than the smallest ambient pressure p to be measured.

[0041] 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 each other in a pressure-equalizing manner via a central connecting opening 32. This allows the measurement of the sound vibrations 14 to be carried out more independently of the ambient pressure p. The connecting opening 32 is separated from the intermediate space 30.

[0042] The first deflection component 24 is designed as a membrane 34 and forms a first electrode 36, and the second deflection component 28 is designed as a membrane 34 and forms a second electrode 38. The counter electrode 22 is arranged between the first and second electrodes 36, 38. This allows a capacitive differential measurement to 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 in particular assigned an individual through-opening 42 in the counter electrode 22.

[0043] The electrode arrangement 20 is mounted on 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.

[0044] The ambient pressure p acting on the pressure-sound sensor 10 and the acting sound vibrations 14 are introduced to the electrode arrangement 20 through one and the same ambient medium 50, for example air.

[0045] Figure 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 of sound vibrations 14 acting from the sensor environment 12 initially comprises providing 54 the pressure-sound sensor 10 described, for example, in Figure 1.

[0046] The electrode arrangement 20 is electrically supplied by applying a basic electrical voltage U to the electrode arrangement 20. The basic voltage is applied between the counter electrode 22 on the one hand and the first electrode 36 and the second electrode 38 on the other. The first and second electrodes 36, 38 are thus electrically connected in parallel.

[0047] 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 vibrations 14. The sound vibrations 14 are measured in a predetermined acoustic frequency range, which preferably corresponds to a dynamic frequency range of the dynamic component.

[0048] The sound vibrations 14 are differentially determined by detecting and evaluating 64 the dynamic frequency range of the dynamic component 62 by comparing an amplified first voltage signal 66 of the first electrode 36 and an amplified second voltage signal 68 of the second electrode 38. To measure the ambient pressure p, an electrical modulation voltage signal 70 is superimposed on the base voltage U, independently of the sound measurement of the sound vibrations 14, which generates a modulation voltage response 72 in the voltage signal 60 depending on the ambient pressure p. This utilizes the fact that the mechanical resonance frequency fr of the deflection components 24, 28 varies depending on the ambient pressure p.

[0049] The ambient pressure p is then determined at least as a function of the modulation voltage response 72 by evaluating the amplitudes of the modulation voltage response 72. Furthermore, amplitudes A' of the modulation voltage signal 70 can be evaluated. The amplitudes of the modulation voltage response 72 can be normalized with the amplitudes A' of the modulation voltage signal 70 and specified 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 resonance frequency fr of the deflection component 24, 28. The ambient pressure p associated with the resonance frequency fr can be calculated using a previously known pressure-resonance relationship 76 as a function of the determined resonance frequency fr, possibly taking temperature into account.This allows the ambient pressure p to be determined from the amplitude maximum of the normalized amplitudes A.

[0050] The modulation voltage signal 70 contains an electrical modulation frequency range 78 that includes at least the frequencies corresponding to the expected pressure-dependent resonance frequencies fr of the deflection components 24, 28 and that lies outside the dynamic frequency range. Preferably, the modulation frequency range 78 further excludes the electrical frequencies corresponding to a mechanical resonance frequency of the counter electrode 22 in order to prevent natural oscillation of the suspended counter electrode 22.

[0051] The modulation voltage signal 70 is implemented as a temporal frequency sweep 80 or a simultaneous broadband frequency superposition. The frequency sweep 80 preferably occurs at least over the modulation frequency range 78, or the frequency superposition comprises at least the modulation frequency range 78.

[0052] As an alternative to the previously described embodiment, the deflection element 18 can be designed 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 vibrations 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.

[0053] Figure 3 shows a pressure-sound sensor during a measurement of the ambient pressure in the method from Figure 2. The pressure-sound sensor 10 is shown 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 thereby causes the oscillation 82 occurring at the resonant frequency. The resonant frequency of the oscillation 82 is dependent on a mechanical stress in the

[0054] Deflection components 24, 28. The resonance frequency can be influenced constructively, for example, by the choice of the connecting means 40, for example a distance between 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 resonance frequency and the dynamic frequency range.

Claims

Patent claims 1 . 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 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 can be deflected relative to the counter electrode (22), Applying an electrical base voltage (U) to the electrode arrangement (20), detecting (58) a voltage signal (60) at the electrode arrangement (20) containing a dynamic component (62) as a function of the sound vibrations (14), determining the sound vibrations (14) as a function of the dynamic component (62), characterized in that 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).

2. Method for combined pressure-sound measurement (52) according to claim 1, characterized in that in order to determine the ambient pressure (p) as a function of the modulation voltage response (72), at least the amplitudes and / or phases of the modulation voltage response (72) are evaluated.

3. Method for combined pressure-sound measurement (52) according to claim 1 or 2, characterized in that the mechanical resonance frequency (fr) of the Deflection element (18) or optionally at least one deflection component (24, 28) of the deflection element (18) is variable depending on 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 resonance frequencies (fr) of the deflection element (18) or of the deflection component (24, 28).

4. 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 resonance frequency of the counter electrode (22).

5. 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 to be the mechanical resonance frequency (fr) of the deflection element (18) or the deflection component (24, 28).

6. Method for combined pressure-sound measurement (52) according to claim 5, characterized in that the ambient pressure (p) assigned to the resonance frequency (fr) is calculated by a previously known pressure-resonance relationship (76) as a function of the determined resonance frequency (fr).

7. Method for combined pressure-sound measurement (52) according to one of claims 3 to 6, characterized in that the sound vibrations (14) are measured in a predetermined acoustic frequency range which corresponds to a dynamic frequency range of the dynamic component, wherein the modulation frequency range (78) lies outside the dynamic frequency range.

8. Method for combined pressure-sound measurement (52) according to one of the preceding claims, characterized in that the modulation voltage signal (70) is a temporal frequency sweep (80) or a simultaneous broadband frequency superposition.

9. 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) at least over the modulation frequency range (78) or the frequency superposition has at least the modulation frequency range (78).

10. Pressure-sound sensor (10) which comprises 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 can be deflected relative to the counter electrode (22) and which is set up to determine an ambient pressure (p) acting from a sensor environment (12) and sound vibrations (14) acting from the sensor environment (12) using a method for combined pressure-sound measurement (52) according to one of the preceding claims.

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