• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A method for operating a resonator will be described below. According to one example of the invention, the resonator is excited by means of a periodic excitation signal which has two or more, but finitely many, signal components each having a defined frequency. A response signal of the sensor at the defined frequencies of the signal components of the excitation signal is determined. Finally, depending on the response signal, model parameters of a parametric model describing the resonator can be calculated.
    公开号:AT516556A1
    申请号:T50879/2014
    申请日:2014-12-03
    公开日:2016-06-15
    发明作者:Alexander Dipl Ing Niedermayer
    申请人:Alexander Dipl Ing Niedermayer；
    IPC主号:
    专利说明:

    Measuring system with resonant sensors and method for operating a resonator
    The invention relates to the field of metrology and measurement signal processing, in particular the excitation of resonators, e.g. resonant sensors, and the evaluation of the resulting sensor signals.
    Resonant sensors can be used to measure a wide variety of physical quantities. Common to all resonant sensors is the property that the quantity to be measured (or the quantities to be measured) influences at least one of the following parameters: the resonant frequency, the quality (< Factor) of the resonance and the damping (Z>) of the resonance (where Q = 1 / D). In other words, the complex, frequency-dependent impedance (or the transmission behavior) of the sensor depends on the measured variable (the measured variables). For a measurement, a resonant sensor is excited to oscillate and the resulting sensor signal is evaluated.
    For example, (micro) mechanical resonators can be used to measure density and viscosity of liquids. However, this is just one of many possible applications. Apart from mechanical resonant circuits sensors can be constructed with the help of electrical resonators.
    In many resonators, the simple model (see Fig. 1) of a damped harmonic resonator must be extended to adequately map the physical conditions. For example, the classic quartz crystal (Quartz Crystal Resonator, QCR). The model of the harmonic resonator is extended by the capacitance formed by the electrodes deposited on the quartz (Butterworth-Van Dyke model, see Fig. 2).
    These elements, which are often referred to as parasitic, form capacitive couplings as well as other effects such as inductive couplings, the electrical properties of the material used and combinations of such influences. In low-damping constellations D (high quality factor Q), the influence of these additional (parasitic) elements can often be neglected. However, these parasitic elements often include frequency dependent components and are subject to variable external influences which can result in significant cross sensitivities in sensor applications. Such effects can be avoided or reduced by evaluating the frequency response of the resonator in a certain range around the resonant frequency and determining the parasitic effects in addition to the behavior of the damped harmonic oscillator.
    There are different ways of excitation of resonators and evaluation of the resulting sensor signals known. One possibility is to regulate the frequency of the excitation signal so that the sensor is operated continuously at a specific operating point of its frequency response (usually the resonance frequency). This principle is used in oscillator circuits and phase locked loops (PLL) and offers the advantage of a continuous excitation, the settling time of the sensor therefore has only a small influence on the achievable measuring rate. However, the evaluation is done only at one operating point of the sensor and is therefore unsuitable for certain measurements, especially in applications with variable parasitic effects.
    Another possibility is to determine the frequency response of the sensor in a certain range around the resonance frequency by the frequency of the excitation signal is continuously or in steps (sweep). This method is used, for example, in spectrum analyzers. It must be taken into account that the sensor has to settle again every time the excitation signal changes, which limits the achievable measuring rate or measuring accuracy. In addition, time-dependent changes of parameters of the resonator in the evaluation can give the appearance of a frequency dependence and consequently measurement errors.
    Another method is to determine the sought parameters of the resonator by the transient or decay behavior. For this purpose, the sensor is excited with a time-limited signal (for example, a pulse). The achievable measurement rate is largely determined by the time constant of the resonator. In the case of very short excitations, very high amplitudes are also required in order to produce a resonator oscillation with sufficient energy and thus to achieve a sufficient signal-to-noise ratio of the sensor signals.
    The object on which the invention is based is to provide a resonant measuring arrangement (resonant sensor including signal processing) which is improved with regard to the above-described prior art and a method for operating resonant sensors.
    The mentioned object is achieved by a method for operating a resonant sensor according to claim 1 and by a measuring arrangement according to claim 7. Various developments and embodiments of the invention are the subject of the appended claims.
    A method of operating a resonator will be described below. According to one example of the invention, the resonator is excited by means of a periodic excitation signal which has two or more, but finitely many, signal components each having a defined frequency. The excitation signal is thus an overlay of a countable number of sinusoids. A response signal of the sensor at the defined frequencies of the signal components of the excitation signal is determined. Finally, depending on the response signal, model parameters of a parametric model describing the resonator can be calculated.
    Furthermore, a measuring arrangement will be described. According to a further example of the invention, the measuring arrangement comprises a resonant sensor, and a signal processing device coupled to the sensor. The signal processing device is designed to excite the resonant sensor by means of a periodic excitation signal. The excitation signal has two or more, but finally many, signal components, each having a defined frequency. The signal processing device is further configured to determine a response signal of the sensor at the defined frequencies of the signal components of the excitation signal and to calculate model parameters of a parametric model which describes the resonant sensor, depending on the response signal.
    In particular, a resonant viscosity sensor is described. Such one usually has an electromechanical or piezoelectric resonator whose resonance (frequency and quality) depends on the viscosity of the liquid in which the sensor is immersed.
    The invention will be explained in more detail with reference to the examples shown in the figures. The illustrations are not necessarily to scale and the invention is not limited to the aspects presented. Rather, emphasis is placed on representing the principles underlying the invention. In the pictures shows:
    FIG. 1 shows examples of different versions of damped harmonic oscillators for modeling resonant sensors;
    Figure 2 Butterworth - Van Dyke Model of a resonant sensor (quartz resonator). The model of a damped harmonic oscillator is extended by the element Co, which depicts the influence of the electrode capacitance;
    FIG. 3 Impulse response of a resonator. The oscillation sounds with the time constant τ = 2Q / oir;
    FIG. 4 shows the excitation and response signal in the frequency domain according to an example of the invention; and
    Figure 5 is a block diagram of the measuring arrangement according to an example of the invention;
    In the figures, the same reference numerals designate the same or similar components, each having the same or similar meaning.
    FIG. 1 shows various damped harmonic oscillators. Mechanical oscillators are formed, for example, by springs (stiffness A), masses (m) and dampers (velocity proportional damping d), electrical resistances R, inductances L and capacitances C. Normally, in the case of mechanical oscillators, a speed v and a force F, in the case of electrical oscillators, a voltage u and current / the state variables of the system. The first or second time derivative of the state variables is here marked with one or two points above the respective symbol. Due to the systematic equivalence of these systems, the differential equations and the frequency-dependent behavior (spectrum) are also equivalent. The latter can be described by the two parameters resonance frequency fr = ωγ / 2π and quality factor Q.
    For many resonators, the simple model of a damped harmonic resonator needs to be extended to adequately map the physical conditions. For example, in the case of the quartz crystal resonator (QCR), where the capacitance formed by the electrodes is represented by an extension of the electrical model by a parallel capacitance Co (Butterworth-Van Dyke model, FIG. 2).
    FIG. 3 shows the impulse response of a vibrator to clarify the meaning of the time constant τ = 2 @ / ωΓ, which describes the decay rate of a system state.
    In order to determine the desired parameters of a resonance (for example fr and Q as well as parasitic quantities) from the frequency response, it is sufficient to determine a certain number (depending on the complexity of the selected model) of points (at different frequencies) of the frequency response.
    The invention relates to a method for determining the frequency response (at a countable number of different frequencies) of a resonator in continuous operation. The spectrum is determined without having to change the excitation signal, the resonator remains in the steady state. The settling time as a consequence of the time constant τ of the resonator is therefore of secondary importance for the measuring rate.
    The excitation signal contains a countable number of different frequencies (FIG. 4). These individual components of the excitation signal can be adapted to the resonator both in terms of their frequency, their amplitude and their phase position. Since the frequencies contained in the excitation signal are known, they can be separated in the response signal without mutual interference and thus the frequency response of the resonator (i.e., for example, the complex impedance of the sensor) at the selected frequencies can be determined.
    The generation of the excitation signal as well as the separation of the individual frequency components in the response signal can be carried out, for example, with an arrangement as shown in FIG. 5. In this example, the excitation signal with the desired frequency components is calculated digitally (signal synthesis) and output with a digital-to-analog converter (DAC) as a time signal. The separation of the individual frequency components can be carried out, for example, in the following manner. With an analog-digital converter, the response signal Α (ή of the sensor is first converted into a time-discrete sequence A [n] = A (n T) at the sampling rate fT = 1 / T (^ denotes the sampling interval), which satisfies the sampling theorem. n £ N {n is the time index of the time-discrete sequence) (discretized).
    With a number of K different frequencies fk {k = 1..Λ) in the excitation signal, for a sequence A [ii [with n = 1 ..N, N> 2K, the linear system of equations
    for the parameters ak and bk are solved. From these two values, for each signal component (with the frequency fk (k = 1... K)) of the response signal A [k , its amplitude
    and the associated phase arctan (öfc / afc) be determined.
    If the frequencies of the signal components contained in the excitation signal are also on a raster hertz raster (that is, the frequencies of the signal components of the excitation signal are each an integer multiple of a fundamental frequency 2nr, then the sum signal (and thus also the response signal A [n]) has a In addition, if fT = ir, ie N, (ie the sampling frequency is a multiple of the frequency spacing of the frequencies of the individual signal components of the excitation signal), the separation of the signal components of the response signal A [n] by applying a Discrete Fourier Transformation For the calculation of the DFT, an optimized algorithm such as the Fast Fourier Transformation (FFT) or the Goertzel algorithm can be used for the calculation of the DFT all frequency components in the transformation window (block) are periodic, no leakage effect occurs and thus no mutual influence of the individual
    Frequency shares on. In this way, the frequency response of the sensor at several points can be determined simultaneously. From the determined points of the frequency response, the parameters of the resonator model (depending on model, quality, damping, spring constant, mass, capacitance, resistance, inductance, etc.) are calculated in a further step.
    By reducing the number of excited (and evaluated) frequencies, the computational effort required for signal processing (in signal generation and signal evaluation, but also in the subsequent calculation of the parameters of the resonator model) can be reduced. However, depending on the applied resonator model, a certain minimum number of different frequencies or specific requirements for their distribution is required.
    According to the example of the invention described above, the frequency response of a resonator is determined at a countable number of different frequencies. The spectrum is determined without the need to change the excitation signal (stationary signal), the system remains in steady state (steady state).
    An important application of resonant sensors is in the measurement of viscosity in liquids. The sensor typically comprises an electromechanical resonator (e.g., a piezoelectric or an electrodynamic resonator) whose resonance (resonant frequency and quality) depends on the viscosity of the liquid in which the resonator is immersed. With the method described here, the resonance curve can be determined in a very simple manner and from this the measured value can be derived for the viscosity sought. Even if the response signal is only evaluated in a few places, it can be used to calculate the complete resonance curve and the measured value with the aid of the electromechanical (parametric) model for the respective resonator.
    权利要求:
    Claims (10)
    [1]
    claims
    A method of operating a resonator, comprising: exciting the resonator by means of a periodic excitation signal having two or more (7V> 2) but finitely many signal components each having a defined frequency fk (k = λ,. and determining a response signal {A [l§ of the resonator at the defined frequencies (fk) of the signal components of the excitation signal.
    [2]
    The method of claim 1, further comprising: calculating model parameters of a parametric model describing the resonator in response to the response signal.
    [3]
    3. The method of claim 1 or 2, wherein the excitation signal is a current or a voltage which is supplied to the resonator.
    [4]
    4. The method according to any one of claims 1 to 3, wherein the defined frequencies {fkj the signal components of the exciting signal are each an integer multiple of a fundamental frequency.
    [5]
    5. The method of claim 1, wherein determining a response signal {A [l <] of the sensor comprises: sampling the response signal {A [k ) generated by the resonator, the response signal applying a plurality of signal components to the signal having defined frequencies; Calculating amplitude and phase or real and imaginary part of the response signal for the defined frequencies (fk).
    [6]
    6. The method of claim 1, wherein determining a response signal {A [l§ of the sensor comprises: sampling the response signal generated by the resonator {A [l§, wherein the response signal comprises a plurality of signal components at the defined frequencies ; Calculating amplitude and phase or real and imaginary part of the defined frequency response signal (fk)] Calculate an impedance of the sensor at the defined frequencies (fk) from the signal components of the excitation signal and signal components of the response signal {A [Q].
    [7]
    7. A measuring arrangement, comprising: a resonator, and a sensor coupled to the signal processing device, which is adapted to: excite the resonator by means of a periodic excitation signal which two or more, but finitely many, signal components each having a defined frequency (fk) having; determine a response signal {A [Q) of the sensor at the defined frequencies (fk) of the signal components of the excitation signal; and calculate model parameters of a parametric model describing the resonator dependent on the response signal.
    [8]
    A measuring arrangement as claimed in claim 7, wherein the signal processing means comprises a sampling unit for sampling the response signal {A [ti] generated by the resonator, the response signal having a plurality of signal components at the defined frequencies; and wherein the signal processing device comprises a processor for calculating the amplitude and phase or the real and imaginary parts of the defined frequency response signal (fk).
    [9]
    A measuring arrangement according to claim 7 or 8, wherein the signal processing means comprises a sampling unit for sampling the response signal {A [k ) generated by the resonator, the response signal having a plurality of signal components at the defined frequencies; and wherein the signal processing device comprises a processor configured to calculate the amplitude and phase or real and imaginary parts of the defined frequency response signal {fk); and calculate an impedance of the sensor at the defined frequencies (fk) from the signal components of the excitation signal and signal components of the response signal {A [l§.
    [10]
    10. A method of measuring a viscosity of a liquid by means of a resonant sensor immersed in the liquid, the method comprising: exciting a resonant sensor by means of a periodic excitation signal comprising two or more (N> 2) but finitely many signal components each having one defined frequencies fk (k = 1..AI); Determining a response signal {A [Q] of the resonant sensor at the defined frequencies (/ *) of the signal components of the excitation signal; Calculating model parameters of a parametric model describing the resonant sensor in response to the response signal; Calculate the viscosity from the model parameters and the parametric model.
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    同族专利:
    公开号 | 公开日
    US20160161388A1|2016-06-09|
    AT516556B1|2017-11-15|
    US11035771B2|2021-06-15|
    DE102015120596A1|2016-06-09|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
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    US6260408B1|1998-05-13|2001-07-17|The United States Of America As Represented By The Secretary Of The Army|Techniques for sensing the properties of fluids with a resonator assembly|
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    ATA50879/2014A|AT516556B1|2014-12-03|2014-12-03|Measuring system with resonant sensors and method for operating a resonator|ATA50879/2014A| AT516556B1|2014-12-03|2014-12-03|Measuring system with resonant sensors and method for operating a resonator|
    DE102015120596.3A| DE102015120596A1|2014-12-03|2015-11-27|Measuring system with resonant sensors and method for operating a resonator|
    US14/957,032| US11035771B2|2014-12-03|2015-12-02|Measurement system with resonant sensors and method for the operation of a resonant sensor|
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