DE102008018671A1 - Contact detection mechanism for e.g. passenger car, has evaluation mechanism producing input signal for resistor-capacitor element, where temperature correction value is determined depending on output signal dependent on input signal - Google Patents

Abstract

The mechanism has a capacitive contact sensor (12) as a part of a resistor-capacitor (RC) element e.g. Ohm's resistor and a capacitor. An evaluation mechanism (10) e.g. microprocessor, corrects an output signal of the capacitive contact sensor by a temperature correction value and produces an input signal (P1) e.g. periodic square wave signal, for the RC element. The capacitive contact sensor is designed as a laminar piezosensor and a piezofoil. The temperature correction value is determined depending on an output signal (P3) of the RC element dependent on the input signal. An independent claim is also included for a method for operating a contact detection mechanism.

Description

The Invention relates to a touch detection device, especially for a motor vehicle, with a capacitive Touch sensor and an evaluation.

From the DE 299 02 607 U1 is a device arrangement for the detection of traffic offenders known, the damage caused by so-called parking bumpers or damage caused by intrusions on the vehicle. In this case, a vibration sensor triggers a camera, which is arranged in the rear parcel shelf of the vehicle and is intended to capture the vibration generator pictorially.

From the EP 0 962 359 A2 a recording apparatus is known for a state immediately after an accident and for people breaking into the vehicle. This condition is documented after detection of a shock with an optical recording and recording device. The same applies to the detection of people breaking into the vehicle.

In the publication "The paint is the solution" from the journal Elektromechanik, April 2002, pages 72 to 75 a piezoelectric resist is described which is arranged to generate a voltage pulse in a switch under a keyboard. The piezoelectric lacquer is produced in such a way that piezoelectric crystals are introduced into the lacquer in order to obtain a printable material mixture. To produce the switches, printed conductors for connecting the switches to insulating films are printed, and the piezoelectric paint is then applied selectively to the conductor positions. The piezoelectric material is then still to be polarized by applying a voltage to the conductors after the switch has been assembled. Such switches are able to replace membrane-type, galvanic switching switching elements with a contact stroke and capacitive switching elements.

To avoid cable lines and associated coupling elements between a movable handle and the associated vehicle is in the DE 103 09 148 A1 proposed to integrate in the handle at least one transmitting unit and in the vehicle, the associated receiving unit, wherein the transmitting unit, the transmission energy from a piezoelectric element, for example, a mounted in the handle piezoelectric paint relates.

A method for monitoring an object parked outdoors, such as aircraft or motor vehicle, is the subject of DE 33 15 831 A1 , The method is based on a capacitive touch detection circuit for detecting a change in frequency when the object is touched. The assistance device in a vehicle for setting various vehicle components according to the user profile of the respective driver detects the specific characteristics of a person sitting on the associated driver's seat via a camera and / or via a speech processor.

From the DE 102 57 125 A1 is a safety device for the protection of pedestrians and cyclists on impact with a front hood of a passenger car to take as known, in which the actuators are controlled to adjust the front cover via a signal of a piezoelectric film sensor.

DE 35 42 697 A1 describes a recording device for a collision with a camera, which is activated by an accelerometer when exceeding a predetermined acceleration value. In the traffic accident documentation system according to the DE 299 18 812 U1 the activation takes place by a shock sensor. The detection device according to the DE 102 23 123 A1 includes at least one sensor for detecting collision with a vehicle and a camera device for optically detecting the subject vehicle.

The DE 10 2006 012 336 A1 discloses a method for touch detection for a motor vehicle having a touch sensor and an on-board evaluation device. In this case, the touch sensor is embodied, for example, as a piezoelectric paint applied to a motor vehicle part and contacted electrically with the evaluation device, the evaluation device generating at least one output signal when an object touches the piezoelectric paint.

It It is an object of the invention to provide an improved touch detection device specify.

The aforementioned The object is achieved by a touch detection device, in particular for a motor vehicle, wherein the touch detection device an RC element, a capacitive Touch sensor as part of the RC element, and an evaluation for correcting an output signal of the capacitive touch sensor by means of a temperature correction value and for generating a Input signal for the RC element, wherein the temperature correction value depending on a dependent on the input signal Output signal of the RC element can be determined.

An evaluation device in the sense of the invention can be, for example, a processor. An evaluation device according to the invention can ever but also be a distributed system with several spatially separated components.

A capacitive touch sensor in the sense of the invention is in particular a piezo sensor or a piezoelectric sensor. A capacitive touch sensor in the sense of the invention can be, for example, a piezolack described at the outset or a piezo film described with reference to the figures. Piezoelectric or piezoelectric sensors are also for example from the DE 100 31 793 C1 known. The EP 0 310 490 B1 discloses a temperature compensated piezoelectric oscillator. Procedures for temperature compensation are also from the DE 42 11 997 A1 , of the DE 34 27 743 A1 , of the EP 1 123 492 B1 and the German Offenlegungsschrift 1 773 187 known.

One RC element according to the invention comprises in particular a resistive Resistor and a capacitor.

In an advantageous embodiment of the invention, it is provided that the output signal of the RC element, which is not caused by the input signal, but the output signal of the capacitive touch sensor which is corrected by means of the temperature correction value, is monitored for exceeding a limit value. Incidentally, it may be provided that the limit value is corrected by means of an inverse temperature correction value and the output signal of the capacitive touch sensor remains uncorrected. This correction of the limit value, which represents an indirect correction of the output signal of the capacitive touch sensor, should also be a correction of the output signal of the capacitive touch sensor according to the invention. If the output signal of the capacitive touch sensor corrected by means of the temperature correction value exceeds the aforementioned limit value, a warning signal is generated or a corresponding warning flag is set. As a result, for example, an audible warning signal can be generated. Other measures when triggering a corresponding warning signal or setting a corresponding warning flag are the DE 10 2006 012 336 A1 refer to.

In Furthermore, an advantageous embodiment of the invention comprises capacitive touch sensor a flat designed Piezo sensor or is designed as a planar piezoelectric sensor. In a further advantageous embodiment of the invention, the capacitive comprises Touch sensor a piezo film or is as a piezo film designed. In a further advantageous embodiment of the invention forms the capacitance of the capacitive touch sensor essentially the capacity of the RC element. In continue Advantageous embodiment of the invention, the input signal is a periodic signal. In a further advantageous embodiment of the Invention, the input signal is substantially a periodic Square wave signal. In a further advantageous embodiment of the invention the temperature correction value as a function of a rectified from the input signal dependent output signal of the RC element determinable. In a further advantageous embodiment of the invention the temperature correction value is a function of in particular arithmetic, mean of a rectified determinable by the input signal dependent output signal of the RC element.

The aforementioned Task is - especially in conjunction with the above Characteristics - in addition by a procedure for the operation of a Touch detection device solved, wherein the touch detection device comprises an RC element and a comprises capacitive touch sensor as part of the RC element, wherein an output signal of the capacitive touch sensor is corrected by means of a temperature correction value, wherein a Input signal for the RC element is generated, and wherein the temperature correction value in response to one of the input signal dependent output signal of the RC element is determined.

In Furthermore, an advantageous embodiment of the invention is the temperature correction value in response to a rectified from the input signal dependent output signal of the RC element determined. In Furthermore, an advantageous embodiment of the invention is the temperature correction value as a function of, in particular arithmetic, mean value a rectified dependent on the input signal Output signal of the RC element determined.

In Furthermore, an advantageous embodiment of the invention is the temperature range or the working area of the filter is selected so that for a maximum sensitivity of the filter in one for automotive use usual range between -40 ° C and 150 ° C, corresponding to a working range of α = 0.15 to 0.38, preferably the maximum of the sensitivity in the Middle of the temperature range of 55 ° C, corresponding to one Filter factor of α = 0.24 is set.

The aforementioned object is also achieved, in particular in conjunction with one or more of the aforementioned features, by a method for operating a touch-detection device, wherein the touch-detection device comprises a piezo-touch sensor, wherein an output signal of the piezo-touch sensor is detected, wherein after detection of the output signal , in particular periodic test signal is applied to the piezo touch sensor, and wherein the previously measured output signal of the Piezo Berüh sensor in response to a change, in particular the attenuation of the test signal is corrected. In an advantageous embodiment of the invention, the test signal is essentially a periodic square wave signal.

The aforementioned Task becomes - in particular in connection with one or several of the aforementioned features - also by a method solved for operating a touch detection device, wherein the touch detection device is a piezo touch sensor comprising, wherein an output signal of the piezo touch sensor is detected, wherein after detection of the output signal on, in particular periodic test signal to a piezo touch sensor comprehensive circuit for generating a response signal applied and wherein the previously measured output signal of the piezo touch sensor depending on a change, in particular the attenuation of the response signal to the Test signal is corrected. In an advantageous embodiment of Invention, the test signal is essentially a periodic square wave signal.

motor vehicle in the context of the invention is in particular an individual on the road usable land vehicle. Motor vehicles in the context of the invention especially not on land vehicles with internal combustion engine limited.

Further Advantages and details will become apparent from the following description of exemplary embodiments. Showing:

1 an embodiment of a motor vehicle in a plan view,

2 the motor vehicle according to 1 in a side view,

3 a sensor capacity as a function of temperature,

4 an embodiment of a touch detection device,

5 (a) three pulses of a pulse train and their distortion,

5 (b) the pulses of the lower half-wave (solid curves) folded upwards about the symmetry axis according to the pulse sequence 5a .

6 an equivalent circuit diagram,

7 (a) Course of a mean voltage value,

7 (b) Sensitivity as a function of a filter factor,

8th another embodiment of a touch detection device,

9 an embodiment of an evaluation and

10 another embodiment of an evaluation.

1 shows a plan view of a motor vehicle with piezoelectric regions B, ie areas with planar piezoelectric touch sensors. These include sections of motor vehicle exterior parts, namely subregions of the front and rear bumpers, sections of the doors and fenders. When the force is applied to the piezoelectric regions, at least one voltage pulse is generated which corresponds to a voltage pulse 4 and 9 is fed to the evaluation device shown in detail. In this case, a contact outside the piezoelectric paint areas is detectable, provided that this contact leads to a force application of the piezoelectric region.

In the motor vehicle, an image recording device K1, z. As a CCD camera, which performs at least one image recording after touch detection - ie output of a warning signal or set a warning flag. In this case, an image, a sequence of images with defined time intervals between the images or a video film can be created. In addition, via a sound recording device 4 For example, a microphone M a arranged in the vehicle telephone handsfree, an audio signal are recorded. In this case, the sound recording device 4 be arranged outside the vehicle cab. The purpose of sound recording is to determine more precisely the cause or the cause of the contact by providing further data, which can be used, for example, for a plausibility check. So that the records can be assigned to exact times and locations, the location data of the navigation system (location of the vehicle), the date and time, which originate, for example, from the reception data of an in-vehicle radio clock, are also recorded.

If further image recording devices 3 are present on the vehicle, also record these pictures. Thus, for example, the data of a front-view camera K4 or K2, the data of a rear-view camera K3 and also side-view cameras K5, K6 can be used for recording. The image recording device K1 is in the embodiment as a rotatable by 360 ° Camera and takes pictures in a horizontal rotation.

2 shows a side view of a motor vehicle with piezoelectric regions B, which are shown in dashed lines. It can be seen in this exemplary embodiment that the piezoelectric paint areas B are subareas of the doors, the fenders and the bumpers. It is not necessary that these areas are arranged on the outside of the vehicle or the vehicle outer skin. An arrangement on the side facing away from the vehicle exterior side for signal detection is possible.

The piezoelectric regions B can be, for example, means in the DE 10 2006 012 336 A1 described piezoelectric paint areas or by means of a piezoelectric film described below (for example Dynasimfolie). In the applications of the piezo sensors for touch detection on large objects, such as the automobile body, elastic and flexible piezo variants should be used in accordance with the design priority. Such piezo sensors are for example the Dynasim films of the manufacturer ALGRA. They have a multilayer technical structure surrounded by polymer film, whereby a certain elasticity is achieved. The Dynasim films are relatively inexpensive, but show much higher temperature dependencies than the above-mentioned piezoceramics.

The temperature dependencies of the signal from dynasim films are due not only to the piezo effect alone, but also to the increase in leakage currents due to deteriorated insulator characteristics of the crystal. According to the manufacturer ALGRA, the temperature-dependent increase in capacity is approx. 0.5% K ^-1 , while the temperature-dependent increase in the leakage current is much higher and amounts to 10% K ^-1 . 3 shows the calculated temperature dependence of the sensor capacitance as a function of the temperature θ. For the Dynasim film, the temperature-dependent increase of the capacity of 0.5% K ^-1 and a typical capacity size of 5 nF at temperature θ = 25 ° C was assumed. The temperature dependencies lead to significant attenuation of the output signal of more than 1% K ^-1 when heated ( M. König, diploma thesis, University of Applied Sciences Braunschweig / Wolfenbüttel, 2005 )

4 shows an embodiment of a touch detection device. The touch detection device has a piezoelectric touch sensor 12 and one as a microprocessor 10 configured evaluation on. In this case, a piezoelectric electrode is connected to ground. The other piezoelectric electrode transmits the signal S after the action of a shock (shown by arrow 15 ).

For applications in the area of touch detection, the frequency spectrum <100 Hz is relevant for Signal S. After the signal amplification by an amplifier 11 signal S is sent via the A / D input E1 to the microprocessor 10 entered for further processing. Detects the microprocessor 10 or the algorithm of its software that a piezo signal has been received, the signal intensity is assessed. If the signal intensity is suprathreshold, ie higher than a certain, in this case very low predefined limit, the microprocessor becomes 10 classify the signal as relevant to the warning and can, by output A1 - by issuing a warning signal or setting a warning flag - provided actions, eg. B. activation of an alarm system, trigger.

To determine the temperature-dependent signal corrections, the piezoelectric touch sensor 12 , as in 4 shown, with an outgoing from the output A2 electrical pulse train P1 (here, for example, rectangular voltage) acted upon. A number of about 10 pulses is advantageous for the pulse train P1. It is advantageous to reduce the amplitude of the pulse sequence P1 to the magnitude of the amplitude of signal S before further processing. Before the pulse sequence P1 input E1 of the microprocessor 10 can be achieved, the amplitude can be reduced by the voltage divider R1 + R2 and the pulse train P2 are generated, so that no signal override by the amplifier 11 happens. The sensor capacitance C _P and the resistance R behave like an RC element with respect to the pulse sequence P2. The influence of this RC element leads to the attenuation and distortion of the pulse sequence P2.

The diode D in 4 serves to ensure that the already low-power signal S is not conducted via the resistors R and R2 to ground and weaker. The use of diode D also causes the input impedance of the amplifier 11 is not adversely reduced by the much low resistance R + R2.

In 5a three pulses of the pulse sequence P2 (solid) are shown. Before the pulses P2 reach the microprocessor input E1, they are attenuated by the filter RC _P (cf. 4 ). The damped signal P3 (dashed) then reaches input E1. In 5 For the sake of simplicity, the voltage drop across the diode D has been disregarded.

6 shows an equivalent circuit diagram of the circuit in 4 (without diode D). At the capacitor C _P are the two voltage amplitudes U _S (of sensor signal S) and U _P3 (from the signal P3). The pulses P3 are applied to the amplifier input if and only if the time change of U _{S is} below a predefined threshold.

Based the already described temperature dependencies of Sensor parameter is a procedure for circuit sizing below and optimization taking into account a concrete Numerical example will be shown.

wobei der Filterfaktor α = 2τ / T = 2τf, die Zeitkonstante τ = RC_P und f die Pulsfrequenz sind. Der Filterfaktor α nimmt mit der Frequenz f und Kapazität C_P zu. Infolge der Abhängigkeit des Filterfaktors α von der Kapazität C_P steigt α mit der Temperatur an. 7a zeigt den Verlauf von U_m als Funktion von Filterfaktor α, wobei U_P2 gleich 1 angenommen wurde. Aus 7a ist ersichtlich, dass U_m zuerst mit der zunehmenden Variable α (bis α ~ 0,5) stark abnimmt, um dann langsamer gegen die Null zu gehen. Hierdurch wurde also auch die mathematische Abhängigkeit des Mittelwerts U_m von der Temperatur ermittelt.The mean value U _{m of} the signal P3 within a half period T / 2 is:

where the filter factor α = 2τ / T = 2τf, the time constant τ = RC _P and f are the pulse frequency. The filter factor α increases with the frequency f and capacitance C _P. As a result of the dependence of the filter factor α on the capacitance C _P , α increases with the temperature. 7a shows the course of U _m as a function of filter factor α, where U _P2 was assumed equal to 1. Out 7a It can be seen that U _m decreases sharply first with the increasing variable α (to α ~ 0,5) and then goes slower towards zero. As a result, the mathematical dependence of the mean value U _m on the temperature was also determined.

For determining a working point with maximum sensitivity for the sensor system, the absolute value of the normalized derivative from the mean value is the variable α, ie | (1 / U _m ) (dU _m / dα) | to calculate. This normalized derivative is a measure of the sensitivity η of the sensor system:

7b shows the curve of | (1 / U _m ) (dU _m / dα) |, ie the sensitivity η of the sensor, as a function of α. The operating point should be where the sensitivity η is highest. The maximum of the sensitivity η is achieved at the filter factor α _m = 0.24.

The relevant temperature range in the automotive sector is between -40 ° C and 150 ° C. If the filter factor α _{m should be} exactly in the middle of the temperature range, ie at the temperature θ = 55 ° C, the C _P value according to 3 equal to 5.8 nF.

A frequency f of 1 kHz is advantageous for pulse sequence P1 or P2, so that a possible mixture of the pulse train P2 and the signal S (<100 Hz) is prevented. From the equation α = 2RC _P f, the value of the filter resistance R = 20.6 kΩ can be calculated by using the already known values of α _m = 0.24, C _P at the temperature θ = 55 ° C and frequency f = 1 kHz result. Thus, the values of filter factor α at θ = -40 ° C and 150 ° C are 0.15 and 0.38, respectively.

In 7a and 7b the already determined working area (α = 0.15 ... 0.38) is marked hatched. How out 7a As can be seen, the mean value U _m , with the assumption U _P2 = 1, varies between 0.85 and 0.64. This makes, assuming a linear temperature dependence for U _m between -40 ° C and 150 ° C (s. 7a ), a negative slope of about 0.1% K ^-1 .

The signal P3 is input several times from the detection unit (in 4 realized by the A / D converter of the microprocessor 10 ). The mean values U _{m of} the sampled voltage values of each half-wave are then calculated. The greater the signal attenuation or the longer the time constant, the smaller are the mean values U _m . Since the time constant τ is proportional to the temperature-dependent capacitance C _P , the mean value U _{m of} each half-cycle will also be temperature-dependent. The mean values U _{m of} each half-wave can be considered as a measure of the temperature-dependent distortion of the pulse sequence P2.

An experimental curve or a standardization table for the temperature dependence of U _{m can be} set up experimentally. The sensor temperature determined by means of the characteristic curve can enable a temperature-dependent amplitude correction for the piezoelectric signal S. A value of the inverse of this characteristic curve is an exemplary embodiment of a temperature correction value in the sense of the invention.

To calculate the mean values U _m , the lower half-waves of the damped pulse sequence, quasi the discharge curve, either software or hardware as in 5b represented (solid curves), rectified. In a software rectification, each sampled voltage value of the lower halfwaves, z. B. u _i in 5a , subtracted from the relative signal amplitude U _P2 . A hardware rectification of the pulse train P3, before it reaches input E1, can be solved by means of a conventional rectifier.

It is advantageous to calculate the mean value U _{M of} all average values U _m . The distribution of the mean values U _m by the value of U _M may then not exceed a predefined empirical value. In the case of too high a variance of the U _m values, a new pulse sequence P1 is to be generated. Other common active and passive filtering of unwanted signals of the pulse train P3 may be provided.

It is also possible, the signal P3 by ei to detect a different input than E1, which is completely (galvanically) separated from input E1. This should, as in 8th shown by the output A0 of a microprocessor 20 (Evaluation) controlled electronic switches 23 in time the connection between the piezoelectric touch sensor 12 and the amplifier 11 then disconnect the piezoelectric touch sensor 12 to contact resistor R and microprocessor input E2. This solution is more complex than that of 4 and requires an electronic switch and an additional microprocessor. In this case, the voltage divider R1 + R2 and the diode D can be dispensed with. Since there is no voltage divider, however, the reduced signal P2 is omitted.

9 shows the operation of the microprocessor 10 using a block diagram. Here, reference numeral designates 31 a rectifier. This is omitted if a corresponding hardware rectifier is provided before the input signal E1. reference numeral 32 denotes an averager and reference numerals 33 a map for generating the temperature correction value δT. reference numeral 34 denotes a correction block for correcting the rectified signal applied to the input E1 by means of the temperature correction value δT. The correction block 34 may for example be designed as a multiplier. reference numeral 35 denotes a limit value monitoring. Exceeds the output of the correction block 34 a certain limit, then generates the limit monitoring 35 a warning signal or sets a warning flag. reference numeral 36 denotes a signal generator for generating the signal P1.

10 shows the operation of the microprocessor 20 , Here, like reference numerals, as in 9 , same or similar elements or functions. With reference number 37 is in 10 a control function to control the switch 23 designated.

10 20

microprocessor = Evaluation device

11

amplifier

12

(Piezoelectric / capacitive) touch sensor

15

arrow

23

switch

31

rectifier

32

averager

33

map

34

correction block

35

limit monitoring

36

signal generator

37

control function

A0, A1, A2

output

B

Area

C _P

capacity

D

diode

E1, E2

entrance

K1, K2, K3, K4, K5, K6

camera

P1

pulse train = Test signal = input signal

P2

pulse train = Signal

P3

pulse train = Reaction signal = output signal of a capacitive touch sensor or an RC element due to an input signal

R, R ₁ , R ₂

ohmic resistance

S

output a capacitive touch sensor due to mechanical effect

U _P1

tension the signal P1

U _P2

Tension over the ohmic resistance R2, voltage of the signal P2

U _P3

tension the signal P3

U _m

Average the rectified voltage of the signal P3

U _S

tension the signal S

.delta.T

Temperature correction value

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 29902607 U1 [0002]
• - EP 0962359 A2 [0003]
• - DE 10309148 A1 [0005]
• - DE 3315831 A1 [0006]
• - DE 10257125 A1 [0007]
• - DE 3542697 A1 [0008]
• - DE 29918812 U1 [0008]
• - DE 10223123 A1 [0008]
• DE 102006012336 A1 [0009, 0015, 0040]
• - DE 10031793 C1 [0013]
• - EP 0310490 B1 [0013]
• - DE 4211997 A1 [0013]
• - DE 3427743 A1 [0013]
• - EP 1123492 B1 [0013]
• - DE 1773187 A [0013]

Cited non-patent literature

• - "The paint is the solution" from the journal Elektromechanik, April 2002, pages 72 to 75 [0004]
• - M. König, diploma thesis, University of Applied Sciences Braunschweig / Wolfenbüttel, 2005 [0041]

Claims (16)

Touch detection device, in particular for a motor vehicle, characterized in that the touch detection device comprises an RC element, a capacitive touch sensor ( 12 ) as part of the RC element, and an evaluation device ( 10 . 20 ) for correcting an output signal (S) of the capacitive touch sensor ( 12 ) by means of a temperature correction value (δT) and for generating an input signal (P1) for the RC element, the temperature correction value (δT) being able to be determined as a function of an output signal (P3) of the RC element dependent on the input signal (P1). Touch detection device according to claim 1, characterized in that the capacitive touch sensor ( 12 ) comprises a planar designed piezoelectric sensor. Touch detection device according to claim 1, characterized in that the capacitive touch sensor ( 12 ) is designed as a planar piezoelectric sensor. Touch detection device according to claim 1, 2 or 3, characterized in that the capacitive touch sensor ( 12 ) comprises a piezo foil. Touch detection device according to claim 1, 2 or 3, characterized in that the capacitive touch sensor ( 12 ) is designed as a piezo film. Touch detection device according to one of the preceding claims, characterized in that the capacitance (C _P ) of the capacitive touch sensor ( 12 ) substantially forms the capacity of the RC element. Touch detection device according to one of preceding claims, characterized in that the input signal (P1) is a periodic signal. Touch detection device according to one of preceding claims, characterized in that the input signal (P1) is essentially a periodic square wave signal is. Touch detection device according to one of preceding claims, characterized in that the temperature correction value (δT) depending on a rectified of the input signal (P1) dependent Output signal (P3) of the RC element can be determined. Touch detection device according to a of the preceding claims, characterized in that the temperature correction value (δT) depending on an average of a rectified one of the input signal (P1) dependent output signal (P3) of the RC element determinable is. Touch detection device according to one of preceding claims, characterized in that the maximum of the sensitivity of the filter in a range between α = 0.15 to 0.38, preferably with the filter factor of α = 0.24 is set. Method for operating a touch detection device, in particular a touch detection device according to one of the preceding claims, characterized in that the touch detection device comprises an RC element, and a capacitive touch sensor ( 12 ) as part of the RC element, wherein an output signal (S) of the capacitive touch sensor ( 12 ) is corrected by means of a temperature correction value (δT), whereby an input signal for the RC element is generated, and wherein the temperature correction value (δT) is determined as a function of an output signal (P3) of the RC element dependent on the input signal (P1). Method according to claim 12, characterized in that that the temperature correction value (δT) in dependence a rectified of the input signal (P1) dependent Output signal (P3) of the RC element is determined. Method according to claim 12 or 13, characterized that the temperature correction value (δT) in dependence one, in particular arithmetic mean of a rectified of the output signal (P3) dependent on the input signal (P1) of the RC element is determined. Method for operating a touch detection device, in particular a touch detection device according to one of claims 1 to 9, characterized in that the touch detection device comprises a piezo touch sensor ( 12 ), wherein an output signal (S) of the piezo touch sensor ( 12 ), wherein after detection of the output signal a, in particular periodic test signal (P1) to a piezo touch sensor ( 12 ) comprehensive circuit for generating a reaction signal (P3) is applied, and wherein the previously measured output signal (S) of the piezo touch sensor ( 12 ) is corrected as a function of a change, in particular the attenuation, of the response signal (P3) with respect to the test signal (P1). A method according to claim 15, characterized ge indicates that the test signal (P1) is essentially a periodic square wave signal.