DE102018207544A1 - Electronic measuring circuit arrangement for generating a response signal to an excitation signal at an output of the electronic measuring circuit arrangement, electronic measuring device for detecting a capacitive measuring signal and method for detecting a capacitive measuring signal to an electronic measuring device - Google Patents

Abstract

The present invention provides an electronic measuring circuit arrangement (1) for generating a response signal (3) to an excitation signal (2) at an output (A) of the electronic measuring circuit arrangement (1), comprising a clock device (4), by means of which a temporal clocking (t ) for the excitation signal (2) can be predetermined; an excitation device (5) which is connected to the clock device (4) and by means of which the excitation signal (2) can be generated according to the timing (t); at least one electronic measuring channel (MK1) which is connected to the excitation device (5) and which comprises a capacitance bridge (KB), wherein the capacitance bridge (KB) comprises a first measuring capacitor (C1M), a second measuring capacitor (C2M), a first reference capacitor ( C1R) and a second reference capacitor (C2R), wherein the first measuring capacitor (C1M) and the second measuring capacitor (C2M) are variable in their capacitance by an external influence and the first reference capacitor (C1R) and the second reference capacitor (C2R) is a constant Have capacitance, wherein the capacity bridge (KB) is connected to the output (A) and the response signal (3) by means of the capacity bridge (KB) can be generated; and a first mechanical oscillating device (11a), which is arranged on the first measuring capacitor (C1M), and / or a second mechanical oscillating device (11b), which is arranged on the second measuring capacitor (C2M), wherein the first mechanical oscillating device (IIa) and / or the second mechanical oscillating device (11b) is coupled to the respective measuring capacitor (C1M; C2M), so that a mechanical energy from the measuring capacitor (C1M; C2M) can be transmitted to the oscillating device (11a; 11b).

Description

The present invention relates to an electronic measuring circuit arrangement for generating a response signal to an excitation signal at an output of the electronic measuring circuit arrangement, to an electronic measuring device for detecting a capacitive measuring signal and to a method for detecting a capacitive measuring signal at an electronic measuring device.

State of the art

When sensor devices, a determination of a measurement signal is usually sought, which attracts as little interference, such as a low noise in the signal in the measurement with it. Particularly regarding the Internet of Things and mobile applications, sensors are required which have high accuracy and are energy-saving. Capacitive sensors are particularly well suited for such applications since the measuring principle itself does not require any current for measuring operation. Furthermore, it is possible to save energy by operating the sensors in a pulsed mode. In a pulsed operation with a pulsed voltage, such as with rectangular profiles, for reading the measuring capacity of the sensor, however, this unwanted broadband can be excited to mechanical natural vibrations, which can be superimposed on the actual measurement signal, a vibration noise.

In the DE 10 2016 107 299 A1 For example, a measuring method, a measuring circuit and a measuring device are described, wherein a signal is determined by means of a random jitter on a scanning signal. A measuring method comprises generating a response signal in response to an excitation signal with a sensor. The method also includes generating a sampling clock signal in accordance with a pseudorandom jitter and sampling the response signal in accordance with the sampling clock signal to determine a plurality of digital samples. The method also includes combining the plurality of digital samples to form a measurement sample.

In "C. Zhao; G.S. Wood; Jianbing Xie; H. Chang; S. Hui Pu; M. Force; A force sensor based on three weakly coupled resonators with ultra-high sensitivity, Sensors and Actuators A 232 (2015) 151 - 162 ", describes coupled vibration systems for amplifying sensor signals.

Disclosure of the invention

The present invention provides an electronic measuring circuit arrangement for generating a response signal to an excitation signal at an output of the electronic measuring circuit arrangement according to claim 1, an electronic measuring device for detecting a capacitive measuring signal according to claim 10 and a method for detecting a capacitive measuring signal at an electronic measuring device according to claim 12 ,

Preferred developments are subject of the dependent claims.

Advantages of the invention

The idea underlying the present invention is to achieve a low-noise signal detection, wherein the signal noise of an output signal of the measuring circuit, such as the natural vibration noise on the measuring signal of this, can be reduced by transmitting the mechanical vibration energy of the measuring capacitors to a coupled oscillatory element and thereby the measuring device can be withdrawn.

According to the invention, the electronic measuring circuit arrangement for generating a response signal to an excitation signal at an output of the electronic measuring circuit arrangement comprises a clock device, by means of which a temporal clocking for the excitation signal can be predetermined; an excitation device connected to the clock means and by means of which the excitation signal can be generated in accordance with the clocking; at least one electronic measuring channel, which is connected to the excitation device and which comprises a capacitance bridge, wherein the capacitance bridge comprises a first measuring capacitor, a second measuring capacitor, a first reference capacitor and a second reference capacitor, wherein the first measuring capacitor and the second measuring capacitor in their capacity by a external influence are variable and the first reference capacitor and the second reference capacitor having a constant capacitance, wherein the capacitance bridge is connected to the output and the response signal is generated by means of the capacitance bridge. Furthermore, the Measuring circuit arrangement, a first mechanical oscillating device, which is arranged on the first measuring capacitor, and / or a second mechanical oscillating device, which is arranged on the second measuring capacitor, wherein the first mechanical oscillating device and / or the second mechanical oscillating device is coupled to the respective measuring capacitor, so that a mechanical energy from the measuring capacitor to the oscillating device is transferable.

Advantageously, the first mechanical oscillating device and / or the second mechanical oscillating device is coupled to the respective measuring capacitor via a coupling mechanism, for example a mechanical coupling mechanism, so that a mechanical energy can be transmitted from the measuring capacitor to the oscillating device arranged thereon.

The response signal advantageously comprises information about a state present and to be measured at the first measuring capacitor and at the second measuring capacitor, for example a prevailing pressure, which can be deduced from the instantaneous capacitances (changes in the capacitance) of the measuring capacitors relative to the reference capacitors. The measurement is carried out by controlling the measuring capacitors with the excitation signal.

In this case, it is advantageously possible that the measuring capacitors and / or the reference capacitors in each case or occasionally comprise only one capacitor or a plurality of capacitors or capacitors connected in parallel.

Advantageously, it is also possible to include a plurality of measuring channels in the measuring circuit arrangement, which advantageously can have the same design, or can have different components or types of connection. The excitation device transmits the excitation signal predetermined in terms of shape and duration as well as in characteristic time scales and oscillation behavior / frequencies (variation behavior, temporal clocking) to the one or more measurement channels by the timing device.

According to a preferred embodiment of the measurement circuit arrangement, the first mechanical oscillation device and / or the second mechanical oscillation device are each coupled to at least one further oscillation device.

According to a preferred embodiment of the measurement circuit arrangement, the first mechanical oscillation device and / or the second mechanical oscillation device comprise a fluidic volume element.

In this case, it is possible that a first mechanical oscillating device comprises a fluidic volume element and a second mechanical oscillating device comprises another vibratable element, for example a diaphragm or a bending beam.

The fluidic volume element is advantageously arranged on a vibrating electrode or membrane of the measuring capacitor and can cover and / or span this electrode or membrane as a cover and cause an attenuation of the oscillation behavior of the electrode or membrane. The fluidic volume element may comprise a cover as cover element and may advantageously delimit a substantially closed fluid volume towards the electrode or membrane of the measurement condenser, advantageously in relation to an environment.

According to a preferred embodiment of the measuring circuit arrangement, the fluidic volume element comprises a plurality of openings for a pressure equalization with an environment of the fluidic volume element.

The openings may advantageously allow passage of a surrounding medium into and out of the fluidic volume element. Such openings may advantageously be arranged in an edge region of a cover element, while a central region of the cover element over the electrode or membrane of the measuring capacitor is advantageously free of openings and may advantageously be covered closed.

According to a preferred embodiment of the measurement circuit arrangement, a further oscillation device is coupled mechanically or capacitively or fluidically to the first mechanical oscillation device and / or to the second mechanical oscillation device.

The mechanical coupling can be advantageously realized by a connecting coupling membrane or a connecting coupling bridge, whereby a mechanical vibration energy can be transferred from a measuring capacitor to a vibrating device.

The fluidic coupling is advantageously realized with an environment of a vibration device, advantageously via an essentially outwardly delimited and open fluidic volume element.

According to a preferred embodiment of the measurement circuit arrangement, the first mechanical oscillation device and / or the second mechanical oscillation device and / or a further oscillation device comprises a membrane or a bending beam.

Here it is possible that only membranes or bending beams are coupled together or membranes and bending beams are mixed with each other coupled.

According to a preferred embodiment of the measuring circuit arrangement, the first and the second measuring capacitor are pressure-sensitive, wherein a capacitance of the first and the second measuring capacitor varies more strongly to a change of an external influence than a capacitance of the first and the second reference capacitor.

Due to the greater variation, it can be advantageously ensured that the measuring capacitors are those components by means of which a pressure is measured.

According to a preferred embodiment of the measuring circuit arrangement, the capacitance bridge comprises a Wheatstone bridge.

According to a preferred embodiment of the measuring circuit arrangement, the measuring channels all comprise a same capacitance and a same mechanical natural frequency.

According to the invention, the electronic measuring device for detecting a capacitive measuring signal comprises an electronic measuring circuit arrangement according to the invention; a signal amplifier means connected to the output of the measurement circuit and adapted to receive the response signal from the output; an analog-to-digital converter device, which is connected downstream of the signal amplifier device; and a filter device configured to receive a signal from the analog-to-digital converter device and configured to generate a digital output signal as a capacitive measurement signal.

The capacitive measuring signal can advantageously already be output in such a form that it can be further processed or at least read out by a digital device, for example a digital circuit, a control device or a computer.

The signal amplifier means may advantageously sample the response signal at a sampling frequency and the filtering means may average the amplified signal over a plurality of samples and excitation signal pulses.

According to a preferred embodiment of the electronic measuring device, this is designed as a pressure sensor, microphone, acceleration sensor or yaw rate sensor.

According to the invention, in the method for detecting a capacitive measuring signal at an electronic measuring device takes place in a method step S1 a provision of an electronic measuring device according to the invention. In a further process step S2 there is a predetermining of a time clocking on a clock generator device and generating an excitation signal with an excitation device based on the time clocking. In one process step S3 there is a driving of at least one electronic measuring channel with the excitation signal, which comprises a capacitance bridge, wherein the capacitance bridge comprises a first measuring capacitor, a second measuring capacitor, a first reference capacitor and a second reference capacitor, wherein the first measuring capacitor and the second measuring capacitor in their capacity by a external influence are variable and the first reference capacitor and the second reference capacitor have a constant capacitance, wherein the capacitance bridge is connected to the output and the response signal is generated by means of the capacitance bridge. Furthermore, in a process step S4 driving a signal amplifier device, an analogue Digital converter device and a filter device, with the response signal and generating a digital output signal as a capacitive measurement signal from the response signal.

The method is advantageously characterized by the features and advantages described in connection with the measuring circuit arrangement and the measuring device, and vice versa.

With regard to the measurement capacitors, the property and size of their oscillatable membrane (electrode) is advantageously known, from which the resonant oscillation behavior can advantageously be derived. Due to the advantageously known sizes and parameters of the measuring capacitors can therefore be easily deduced, for example after comparison with reference capacitors, on the pressure at the measuring capacitor.

The mechanical vibration energy of the measuring capacitor is advantageously transferred to the mechanical oscillating device. In other words, the oscillation energy is transferred from a component which is capacitively active in the measuring circuit arrangement to a component which is capacitively ineffective in the measuring circuit arrangement, advantageously the mechanical first or second or further oscillating device. The first and / or second and / or further oscillating device is advantageously not electrically connected to the measuring channel. The mechanical oscillation energy is advantageously localized and damped in the first and / or second and / or further oscillating device, whereby the oscillatory noise caused by the read-out voltage pulses in the measuring channel can be reduced. Therefore, after a characteristic energy transfer time to the first and / or second and / or further oscillating device, the response signal advantageously comprises no or only slight oscillation noise due to the excitation signal.

By advantageously significantly reduced vibration noise, an improved measurement resolution of the measuring device can be achieved, for example, advantageous for capacitive MEMS sensors.

According to a preferred embodiment of the method takes place in a process step S5 determining a measured variable from the measuring signal only after a characteristic settling time of the first mechanical oscillating device and / or the second mechanical oscillating device.

The characteristic transient time is advantageously that time which is required by the system of the measurement channel and the first mechanical oscillation device and / or the second mechanical oscillation device and / or the further oscillation device to transfer the oscillation energy from the measurement channel largely to the oscillation device (s).

The determination of the measured variable, advantageously a signal detection, advantageously begins after a characteristic settling time, which can also be a characteristic decay time of the oscillation, for example as t ² = 2m / d, where m is the mass and d is the damping constant of the oscillating system. After the settling time or the decay time, the measuring channel and the measuring device advantageously have no or greatly reduced oscillation noise, since the mechanical oscillation energy of the oscillation noise has advantageously been transferred to the first and / or second and / or further oscillating device.

According to a preferred embodiment of the method takes place in a process step S5 determining a measured variable from the measurement signal in a quiescent state of the first measurement capacitor and / or the second measurement capacitor, wherein the idle state results after a characteristic beat frequency of the respective measurement capacitor and the coupled mechanical oscillation device.

As an alternative embodiment for determining the measured variable after a characteristic settling time, the determination can take place in the idle state, if advantageous oscillating the oscillation energy according to a beat between the electrode or membrane of the measuring capacitor and the oscillating device back and forth.

By means of a pulsed readout method, a sensor device, in particular a capacitive sensor device, can be improved in its energy-saving efficiency. By a rectangular pulsed excitation signal, the measuring circuit and its components can be unintentionally excited to mechanical vibrations. In a capacitor, such as the measuring capacitor, caused by the pulsed voltage electrical potential differences between the two electrodes, resulting in a relative attractive force, whereby natural mechanical vibration modes are excited. In this way, a small dynamic noise component is superimposed on the actual static measurement signal. However, this effect can also occur with other time-variable excitation signal patterns. For example, can a fundamental mode of the mechanical natural oscillations lead to an electrically measurable oscillation behavior of the measuring capacitors, in particular of the measuring capacitors, which leads to a vibration noise of a response signal at the output. The damping or quality of a mechanically oscillating system determines its decay time. When capacitive measurement, the system advantageously has a low mechanical vibration quality with respect to a read pulse excitation.

Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings.

list of figures

The present invention will be explained in more detail with reference to the exemplary embodiments indicated in the schematic figures of the drawing.

• 1 eine schematische Darstellung einer elektronischen Messvorrichtung mit einer elektronischen Messschaltungsanordnung gemäß eines Ausführungsbeispiels der vorliegenden Erfindung;
• 2 eine schematische Anordnung einer ersten mechanischen Schwingvorrichtung mit mehreren weiteren Schwingvorrichtungen in Draufsicht gemäß eines Ausführungsbeispiels der vorliegenden Erfindung;
• 3 eine schematische Darstellung eines ersten Messkondensators mit einer ersten mechanischen Schwingvorrichtung mit einem fluidischen Volumen gemäß eines Ausführungsbeispiels der vorliegenden Erfindung;
• 4 eine schematische Darstellung eines ersten Messkondensators mit einer ersten mechanischen Schwingvorrichtung im Querschnitt längs eines Schnittes Q-Q' aus 2 gemäß eines Ausführungsbeispiels der vorliegenden Erfindung;
• 5 eine schematische Darstellung eines ersten Messkondensators mit einer ersten mechanischen Schwingvorrichtung im Querschnitt längs eines Schnittes Q-Q' aus 2 gemäß eines weiteren Ausführungsbeispiels der vorliegenden Erfindung;
• 6 eine schematische Darstellung einer Abfolge von Verfahrensschritten gemäß eines Ausführungsbeispiels der vorliegenden Erfindung; und
• 7 eine zeitliche Darstellung einer Schwebefrequenz mit einem Ruhezustand.

Show it:

• 1 a schematic representation of an electronic measuring device with an electronic measuring circuit arrangement according to an embodiment of the present invention;
• 2 a schematic arrangement of a first mechanical vibrating device with a plurality of other oscillating devices in plan view according to an embodiment of the present invention;
• 3 a schematic representation of a first measuring capacitor with a first mechanical oscillating device with a fluidic volume according to an embodiment of the present invention;
• 4 a schematic representation of a first measuring capacitor with a first mechanical oscillating device in cross section along a section QQ 'from 2 according to an embodiment of the present invention;
• 5 a schematic representation of a first measuring capacitor with a first mechanical oscillating device in cross section along a section QQ 'from 2 according to another embodiment of the present invention;
• 6 a schematic representation of a sequence of method steps according to an embodiment of the present invention; and
• 7 a temporal representation of a hover frequency with a resting state.

In the figures, like reference numerals designate the same or functionally identical elements.

1 shows a schematic representation of an electronic measuring device with an electronic measuring circuit arrangement according to an embodiment of the present invention.

The electronic measuring device 10 for detecting a capacitive measuring signal S includes electronic measurement circuitry 1 wherein a signal amplifier means 7 with the exit A the measuring circuit arrangement 1 is connected and that of the measuring channel MK1 output response signal 3 from the measurement circuitry 1 receives. From the exit A gone is the signal amplifier device 7 below an analog-to-digital converter device 8th downstream, which in turn a filter device 9 is downstream, which from the response signal 3 a capacitive measurement signal S as a digital output signal of the measuring device 10 generated. The capacitive measuring signal S may itself consist of at least two partial signals, each of which is dependent on the signals of the first bridge sections KB11 and KB12 can come. In the electrical measuring circuit arrangement 1 generates a clock device 4 a temporal clocking t , With the clock device 4 is an excitation device 5 connected, wherein a clock signal with the timing t to the excitation device 5 is forwarded. The excitation device 5 generated based on the timing t , an excitation signal 2 , For example, a rectangular readout voltage pulse, with which an electronic measuring channel MK1 is controlled. The first electronic measuring channel MK1 includes a common first input node X1 in which a first bridge section KB11 and a second bridge section KB12 of the first measuring channel MK1 are interconnected. Here, the measuring channel includes MK1 a capacity bridge KB , with advantageous the first and the second bridge section KB11 and KB12 , The capacity bridge KB1 further comprises a second common input node Y1 in which the two bridge sections KB11 and KB12 interconnected with each other. Like the first entrance node X1 is also the second entrance node Y1 with the excitation device 5 interconnected and can be at a ground potential. The first bridge section KB11 includes a first measuring capacitor 1M and a first reference capacitor C1R , which in the first bridge section KB11 connected in series with each other. The second bridge section KB12 includes a second measuring capacitor C2M and a second reference capacitor C2R , which in the second bridge section KB12 are connected in series with each other, but with respect to the two input nodes X1 and Y1 advantageous in reverse order as the capacitors in the first bridge section KB11 , In each of the bridge sections, the signal between the measuring capacitor and the reference capacitor to the output A be led out.

2 shows a schematic arrangement of a first mechanical oscillating device with several other oscillating devices in plan view according to an embodiment of the present invention.

The first mechanical oscillating device 11a can be advantageous to the first measuring capacitor 1M or on a second measuring capacitor C2M be arranged and continue with a first 11a , a second one 11b or another mechanical oscillating device 11c connected, advantageously be coupled mechanically vibrating. A mechanical oscillating energy may advantageously be from the measuring capacitor (first or second) to the first or second oscillating device 11a or 11b and on to the further oscillating device 11c Advantageously be transferred partially or completely. The first or second oscillating device 11a or 11b can be advantageous over a coupling channel K with the further oscillating device 11c be coupled and vibratory coupled. The coupling channel can be, for example, a vacuum, a gas, a spring, a fluid or a bridge component between oscillatable membranes or electrodes.

The first or second oscillating device 11a or 11b can simultaneously with several other vibrating devices 11c Advantageously each own coupling channels K be connected. The other vibrating devices 11c can laterally around the first or second vibrating device 11a or 11b be arranged in a row or otherwise. Instead of or in addition to the first or second oscillating device 11a or 11b can the at least one further oscillating device 11c also with the oscillating electrode / membrane of the measuring capacitor via the coupling channels K be coupled. In this case, the measuring capacitor advantageously comprises the electrode / membrane which is effective for the capacitive measurement and which can be coupled in an oscillatable manner to the first and the further oscillating devices, and the further oscillating devices 11c or the first oscillating device 11a a capacitive for measurement ineffective membrane, which may be coupled to the membrane of the measuring capacitor via the coupling channel. The strength of the couplings of the coupling channels can be different or equal to each other. The coupled vibratory devices may have a different or the same mechanical structure or dimensions. The connecting line Q - Q 'refers to an arrangement of a first oscillating device 11a on the first measuring capacitor 1M ,

3 shows a schematic representation of a first measuring capacitor with a first mechanical oscillating device with a fluidic volume according to an embodiment of the present invention.

Above the first measuring capacitor 1M can advantageously on one of its electrodes e, which is excited by the readout voltage pulse to mechanical oscillations and is effective for capacitive measurement, a fluidic volume element FV be arranged, for example, directly on which advantageous the entire electrode e, which may be formed in or as a membrane spans. The fluidic volume element may comprise a liquid and is part of the first or second oscillating device 11a or 11b , The first or second oscillating device 11a or 11b advantageously comprises a cover element DE , Advantageously, a mechanical cover element which the fluidic volume element FV covers on a side facing away from the electrode e. The cover element DE can be beneficial openings O which extend from the environment to the fluidic volume element FV can extend. The openings O can advantageously be formed in a lateral edge region of the cover element, the middle region of the cover element being free from openings O may be and the fluidic volume element FV can cover vibration damping. In this way, advantageously, the central region can be formed free of openings, and there a high attenuation in particular a Grundigenmode be achieved, since the mechanical deflection of the fundamental mode in the central region can be particularly strong. Through the openings O can advantageously a surrounding medium in the first or second oscillating device 11a or 11b penetrate, whereby a pressure equalization with the environment can be achieved. The fluidic volume element advantageously increases a spring constant of a spring effect, which arises due to the fluid. The electrode e or membrane of the measuring capacitor represents a mechanical oscillator with a mechanical spring constant, to which advantageously still the spring constant of the fluid spring of the fluidic volume element FV come in addition, which may also be a gas spring if the fluidic volume element is advantageous FV includes a gas. This advantageously increases a resonance frequency of the measuring capacitor and oscillating device system 11a / 11b and advantageously suppresses mechanical oscillation (due to inherent noise modes), since higher frequencies in the electrical excitation spectrum can be less strongly contained and consequently less excitation can occur. Furthermore, the vibration energy can be dissipated faster by a fluid friction, whereby the vibration of the natural vibration noise can come to rest more quickly. The electrode with the volume element arranged on it FV may advantageously extend beyond the other electrode of the measuring capacitor or be equal to this.

4 shows a schematic representation of a first measuring capacitor with a first mechanical oscillating device in cross section along a section Q-Q ' out 2 according to an embodiment of the present invention.

The first measuring capacitor 1M Advantageously, two electrodes capacitively effective for the measurement e, which individually or both via a coupling channel K , with another oscillatable membrane of the first or second oscillating device 11a / 11b can be coupled.

At the coupling channel K it may be a coupling membrane, via which a membrane of the oscillating device 11a / 11b can be excited to swing. On this membrane can advantageously be arranged a vibration damping element, such as a layer of polyimide. The membrane of the vibrating device 11a / 11b is advantageously not electrically connected to the measuring capacitor or the measuring bridge. In this case, a localization of the oscillation in the oscillating device advantageously takes place 11a / 11b ,

5 shows a schematic representation of a first measuring capacitor with a first mechanical oscillating device in cross section along a section Q-Q ' out 2 according to another embodiment of the present invention.

The first measuring capacitor 1M advantageously comprises two capacitive electrodes for measuring e , which via a trained as a mechanical coupling bridge coupling channel K with another oscillatable membrane of the first or second oscillating device 11a / 11b can be coupled, advantageously via a mechanical bridge as a coupling channel K , which on the outside to the electrode e and to a membrane of the vibrating device 11a / 11b can be tied. The bridge advantageously comprises an electrode e / membrane of the measuring capacitor 1M and the membrane M the first oscillating device 11a partially or wholly spanning vibratory plate or mechanical connection, which is supported on the electrode e / membrane and membrane M can be arranged and vibrational energy between the electrode e / membrane and the membrane M can transfer. The membrane M may also include an electrode, whereby a same vibration behavior can be generated as that of the coupled measuring capacitor 1M , The measurement on the measuring capacitor 1M advantageously takes place in a rest position of the electrode e / membrane, so if a large part or the entire vibration energy on the membrane M of the oscillating device 11a / 11b lies.

Via a strength of the coupling by means of the coupling channel can be advantageously set a characteristic beat frequency, with which the vibration energy between the electrode e / membrane of the measuring capacitor 1M and the first or second oscillating device 11a / 11b can oscillate back and forth.

mit den Kreisfrequenzen ${\omega }_1=\sqrt{\frac{k_m}{m}}\text{ und }{\omega }_2=\sqrt{\frac{k_m+2k_g}{m}\text{.}}$

(xi - Position des Schwingers, B - Amplitude, t - Zeit, φi - Phasenlagen der beiden gekoppelten Schwinger, km - Federkonstante, kg - Kopplungsfederkonstante). Als Schwebungsfrequenz ωS=1/TS bezeichnet man dabei ${\omega }_S:=\frac{{\omega }_2-{\omega }_1}{2}.$

The oscillation of the effective capacity can advantageously be described as follows: $$x_1=B\text{cos}\left({\omega }_{1}t+{\phi }_1\right)+B\text{cos}\left({\omega }_{2}t+{\phi }_2\right)=2B\cdot \text{cos}\left(\frac{\left({\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="DE102018207544A1\_0004.png,DE102018207544A1\_0007.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1+{\omega }_2\right)\mathrm{<figure-callout\; id="1"\; label="t\; +\; \phi "\; filenames="DE102018207544A1\_0004.png,DE102018207544A1\_0007.png"\; state="\{\{state\}\}">t\; </figure-callout>}+{\phi }_{}{}_1+{\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102018207544A1\_0004.png,DE102018207544A1\_0007.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2}{2}\right)\cdot \text{cos}\left(\frac{\left({\omega }_1-{\omega }_2\right)t+\left({\phi }_1-{\phi }_2\right)}{2}\right).$$

with the angular frequencies ${\omega }_1=\sqrt{\frac{k_m}{m}}\text{and}{\omega }_2=\sqrt{\frac{k_m+2k_G}{m}\text{,}}$

(xi position of the oscillator, B amplitude, t time, φi phase angles of the two coupled oscillators, km spring constant, kg coupling spring constant). The beating frequency ωS = 1 / TS is called ${\omega }_S:=\frac{{\omega }_2-{\omega }_1}{2},$

6 shows a schematic representation of a sequence of method steps according to an embodiment of the present invention.

In the method for detecting a capacitive measuring signal on an electronic measuring device, the method steps are advantageously carried out in the order given S1 to S5 , In the process step S1 a provision of an electronic measuring device according to the invention ( 10 ). In a further process step S2 there is a predetermination of a time clock (t) at a clock device ( 4 ) and generating an excitation signal ( 2 ) with an excitation device ( 5 ) based on the timing (t); as well as in one process step S3 a driving of at least one electronic measuring channel ( MK1 ) with the excitation signal ( 2 ), which is a capacity bridge ( KB ), the capacity bridge ( KB ) a first measuring capacitor ( 1M ), a second measuring capacitor ( C2M , a first reference capacitor ( C1R ) and a second reference capacitor ( C2R ), wherein the first measuring capacitor ( 1M ) and the second measuring capacitor ( C2M ) are variable in their capacity by an external influence and the first reference capacitor ( C1R ) and the second reference capacitor ( C2R ) have a constant capacity, the capacity bridge ( KB ) with the output ( A ) and the response signal ( 3 ) by means of the capacity bridge ( KB ) is produced. In a further process step S4 a drive of a signal amplifier device ( 7 ), an analog-to-digital converter device ( 8th ), and a filter device ( 9 ), with the response signal ( 3 ) and generating a digital output signal as a capacitive measurement signal ( S ) from the response signal ( 3 ). In a further process step S5 can a determination of a measured variable from the measuring signal ( S ) after a characteristic settling time of the first mechanical oscillating device ( IIa ) and / or the second mechanical oscillating device ( 11b) respectively. Alternatively, in the process step S5 also determining a measured variable from the measuring signal (S) in a quiescent state of the first measuring capacitor ( 1M ) and / or the second measuring capacitor ( C2M ), wherein the idle state after a characteristic beat frequency of the respective measuring capacitor ( 1M ; C2M ) and the coupled mechanical oscillating device ( 11a ; 11b) results.

7 shows a temporal representation of a beat frequency with a resting state.

The idle state can advantageously be used on the measurement capacitor for a measurement with low intrinsic oscillation noise of the sensor (measuring device), advantageously during a signal acquisition window which can settle after half a period of the beat frequency at the electrode / membrane of the measurement capacitor. Advantageously, the signal acquisition window may comprise a width of one-tenth of the beat frequency or less.

Although the present invention has been fully described above with reference to the preferred embodiment, it is not limited thereto but may be modified in a variety of manners.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102016107299 A1 [0003]

Claims (14)

Electronic measuring circuit arrangement (1) for generating a response signal (3) to an excitation signal (2) at an output (A) of the electronic measuring circuit arrangement (1) - A clock means (4) by means of which a timing (t) for the excitation signal (2) can be predetermined; - An excitation device (5) which is connected to the clock means (4), and by means of which the excitation signal (2) according to the timing (t) can be generated; - At least one electronic measuring channel (MK1) which is connected to the excitation device (5) and which comprises a capacitance bridge (KB), wherein the capacitance bridge (KB) a first measuring capacitor (C1M), a second measuring capacitor (C2M), a first reference capacitor (C1R) and a second reference capacitor (C2R), wherein the first measuring capacitor (C1M) and the second measuring capacitor (C2M) are variable in their capacitance by an external influence and the first reference capacitor (C1R) and the second reference capacitor (C2R) a have constant capacitance, wherein the capacitance bridge (KB) is connected to the output (A) and the response signal (3) by means of the capacity bridge (KB) can be generated; and a first mechanical oscillating device (11a), which is arranged on the first measuring capacitor (C1M), and / or a second mechanical oscillating device (11b), which is arranged on the second measuring capacitor (C2M), wherein the first mechanical oscillating device (IIa) and / or the second mechanical oscillating device (11b) is coupled to the respective measuring capacitor (C1M; C2M), so that a mechanical energy from the measuring capacitor (C1M; C2M) can be transmitted to the oscillating device (11a; 11b). Electronic measuring circuit arrangement (1) according to Claim 1 in which the first mechanical oscillating device (IIa) and / or the second mechanical oscillating device (11b) are each coupled to at least one further oscillating device (11c). Electronic measuring circuit arrangement (1) according to Claim 2 in which the first mechanical vibration device (IIa) and / or the second mechanical vibration device (11b) comprise a fluidic volume element (FV). Electronic measuring circuit arrangement (1) according to Claim 3 in that the fluidic volume element (FV) comprises a plurality of openings (O) for pressure equalization with an environment of the fluidic volume element (FV). Electronic measuring circuit arrangement (1) according to Claim 2 . 3 or 4 in which the further oscillating device (11c) is coupled mechanically or capacitively or fluidically to the first mechanical oscillating device (11a) and / or to the second mechanical oscillating device (11b). Electronic measuring circuit arrangement (1) according to one of Claims 1 to 5 in which the first mechanical vibration device (IIa) and / or the second mechanical vibration device (11b) and / or the further vibration device (11c) comprises a diaphragm or a bending beam. Electronic measuring circuit arrangement (1) according to one of Claims 1 to 6 wherein capacitance of the first and second measuring capacitors (C1M; C2M) is more sensitive to a change of an external influence than a capacitance of the first and second reference capacitors (C1R C2R). Electronic measuring circuit arrangement (1) according to one of Claims 1 to 7 in which the capacity bridge (KB) comprises a Wheatstone bridge. Electronic measuring circuit arrangement (1) according to one of Claims 1 to 8th , in which the measuring channels all have an equal capacitance and the measuring capacitors (C1M, C21M) have the same mechanical natural frequency. Electronic measuring device (10) for detecting a capacitive measuring signal (S), comprising - an electronic measuring circuit arrangement (1) according to one of Claims 1 to 9 ; - A signal amplifier means (7) which is connected to the output (A) of the measuring circuit (1) and which is adapted to receive the response signal (3) from the output (A); - an analog-to-digital converter device (8), which is connected downstream of the signal amplifier device (7); and - a filter device (9), which is adapted to receive a signal of the analog-to-digital converter device (8), and which is adapted to generate a digital output signal as a capacitive measurement signal (S). Electronic measuring device (10) after Claim 10 , which is designed as a pressure sensor, microphone, acceleration sensor or rotation rate sensor. Method for detecting a capacitive measuring signal (S) at an electronic measuring device (10), comprising the steps: S1) providing an electronic measuring device (10) according to one of the Claims 10 or 11 ; S2) predetermining a timing (t) at a timing device (4) and generating an excitation signal (2) with an excitation device (5) based on the timing (t); S3) activating at least one electronic measuring channel (MK1) with the excitation signal (2), which comprises a capacitance bridge (KB), wherein the capacitance bridge (KB) comprises a first measuring capacitor (C1M), a second measuring capacitor (C2M), a first reference capacitor ( C1R) and a second reference capacitor (C2R), wherein the first measuring capacitor (C1M) and the second measuring capacitor (C2M) are variable in their capacitance by an external influence and the first reference capacitor (C1R) and the second reference capacitor (C2R) is a constant Having capacitance, wherein the capacitance bridge (KB) is connected to the output (A) and the response signal (3) is generated by means of the capacitance bridge (KB); and S4) driving a signal amplifier device (7), an analog-to-digital converter device (8), and a filter device (9) with the response signal (3) and generating a digital output signal as a capacitive measurement signal (S) from the response signal (3). , Method according to Claim 12 in which, in a method step S5, a determination of a measured variable from the measuring signal (S) takes place only after a characteristic settling time of the first mechanical oscillating device (IIa) and / or the second mechanical oscillating device (11b). Method according to Claim 12 in which, in a method step S5, a measured variable is determined from the measuring signal (S) in an idle state of the first measuring capacitor (C1M) and / or of the second measuring capacitor (C2M), wherein the idle state follows a characteristic beat frequency of the respective measuring capacitor (C1M C2M) and the coupled mechanical oscillating device (11a, 11b).

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