Vibronic Sensor

• US 20160109285A1
• Filed: 10/13/2015
• Published: 04/21/2016
• Est. Priority Date: 10/15/2014
• Status: Active Grant

• Current Assignee: Endress+Hauser SE+Co. KG (Endress+Hauser AG)
• Original Assignee: Endress + Hauser GmbH + Company KG (Endress+Hauser AG)
• Inventors: Brengartner, Tobias, Gersbacher, Lukas
• Granted Patent: US 10,401,215 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01F 1/20 by detection of dynamic effects of the flow
• CPC Class Codes: G01F 1/66 by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
• CPC Class Codes: G01F 23/284 Electromagnetic waves
• CPC Class Codes: G01F 23/296 Acoustic waves
• CPC Class Codes: G01F 23/2967 for discrete levels
• CPC Class Codes: G01F 23/802 Particular electronic circuits for digital processing equipment
• CPC Class Codes: G01H 11/06 by electric means
• CPC Class Codes: G01N 2009/006 vibrating tube, tuning fork
• CPC Class Codes: G01N 9/002 using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis G01N9/34 takes precedence

Abstract

A method to determine and/or monitor at least one process variable of a medium with at least one vibration-capable unit. The vibration-capable unit is excited to mechanical vibrations by means of an electrical excitation signal of an adjustable frequency; wherein the mechanical vibrations are transduced into a received electrical signal, which is characterized at least by a frequency and/or a phase and/or an amplitude. The excitation signal is generated based on the received signal; wherein the voltage values of the received signal are sampled at specified predetermined points in time, starting from the excitation signal. The real part and the imaginary part of the received signal are determined from the sampled voltage values of the received signal by means of a Goertzel algorithm; wherein at least one Goertzel coefficient—in particular the number of the sample values and/or an operating frequency and/or a sample frequency—is provided for performing the Goertzel algorithm. At least the current phase and/or the current amplitude of the received signal are calculated from the real part and the imaginary part of the received signal; wherein the frequency of the excitation signal is adjusted such that a predeterminable phase shift is present between the excitation signal and the received signal; and wherein the at least one process variable is determined.

Claims

1-17. -17. (canceled)

18. A method to determine and/or monitor at least one process variable of a medium with at least one vibration-capable unit, comprising the steps of:

exciting the vibration-capable unit to mechanical vibrations by means of an electrical excitation signal of an adjustable frequency;

transducing the mechanical vibrations into a received electrical signal, which received electrical signal is characterized at least by a frequency and/or a phase and/or an amplitude, said electrical excitation signal is generated based on said received signal;

sampling the voltage values of said received electrical signal at specified predetermined points in time, starting from said electrical excitation signal;

determining the real part and imaginary part of said received electrical signal from the sampled voltage values of said received signal by means of a Goertzel algorithm, wherein at least one Goertzel coefficient—

in particular the number of the sample values and/or an operating frequency and/or a sample frequency—

is provided for performing the Goertzel algorithm;

calculating at least the current phase and/or the current amplitude of said received electrical signal from said real part and imaginary part of said received electrical signal; and

adjusting the frequency of said electrical excitation signal such that a predeterminable phase shift is present between said electrical excitation signal and said received electrical signal, and wherein the at least one process variable is determined.

19. The method according to claim 18, wherein:

the working frequency is set to the frequency of said electrical excitation signal.

20. The method according to claim 18, wherein:

the sampling frequency is selected as a whole-number multiple of the frequency of said electrical excitation signal.

21. The method according to claim 19, wherein:

a whole-number multiple of a period of said electrical excitation signal is selected for the number of said sample values.

22. The method according to claim 20, wherein:

two or four times the frequency of said excitation signal is set as said sampling frequency.

23. The method according to claim 18, wherein:

the Goertzel algorithm is used across multiple periods of said electrical excitation signal.

24. The method according to claim 18, wherein:

said electrical excitation signal is a square wave signal or a sine signal.

25. The method according to claim 18, wherein:

said predeterminable phase shift is set using the quotient from the number of said sample values and said sampling frequency by means of a time shift of said sample values in relation to said excitation signal.

26. The method according to claim 18, wherein:

said predeterminable phase shift is 90°

.

27. The method according to claim 18, further comprising the step of:

subdividing a measurement period into at least two time intervals, wherein;

respectively a first predeterminable phase shift is set in a first time interval, and a second predeterminable phase shift is set in a second time interval.

28. The method according to claim 18, wherein:

a function defined by the quotient of the real part and the value of the imaginary part of said received signal, or the inverse of this function for the control deviation, is used to set said predeterminable phase shift.

29. The method according to claim 28, wherein:

said control deviation is limited, in particular to +/−

1.

30. A device to determine and/or monitor at least one process variable of a medium, comprising:

at least one mechanical vibration-capable unit;

a control unit;

an electromechanical transducer unit which is designed to excite said at least one mechanical vibration-capable unit to mechanical vibrations based on an electrical excitation signal of an adjustable frequency, and to receive the mechanical vibrations and transduce them into a received electrical signal, which received signal is characterized at least by a frequency and/or a phase and/or an amplitude; and

an electronic unit with a microprocessor which is designed;

to generate the electrical excitation signal based on the received signal, to sample the voltage values of the received signal at defined predetermined points in time, to determine the real part and imaginary part of the received signal from the sampled voltage values of the received signal by means of a Goertzel algorithm, wherein;

at least one Goertzel coefficient—

in particular the number of the sample values and/or a working frequency and/or a sample frequency—

is provided for performing the Goertzel algorithm, to calculate at least the current phase and/or the current amplitude of the received signal from the real part and imaginary part of the received signal;

with said control unit that is designed to set the frequency of the excitation signal such that a predeterminable phase shift is present between the excitation signal and received signal; and

said electronic unit is designed to determine the at least one process variable.

31. The device according to claim 30, wherein:

said microprocessor is a low-power microprocessor.

32. The device according to claim 30, wherein, further comprising:

an anti-aliasing filter, in particular an adaptive switched-capacitor filter.

33. The device according to claim 30, wherein:

said at least one process variable is provided by the fill level, the density, or the density of the medium in a container;

or by the flow rate of the medium through a tube.

34. The device according to claim 30, wherein:

said electromechanical transducer unit is provided by a piezoelectric actuator or an electromagnetic actuator.