Method for calibration or adjustment of any oscillatable unit

Patent metadata

Field	Value
Publication number	US-10078005-B2
Application number	US-201414896937-A
Country	US
Kind code	B2
Filing date	May 19, 2014
Priority date	Jun 13, 2013
Publication date	Sep 18, 2018
Grant date	Sep 18, 2018

Abstract

A method for calibration or adjustment of any oscillatable unit with a mathematical model describing the oscillatable unit, wherein the oscillatable unit interacts with a medium located in a container, comprising the steps as follows: exciting the oscillatable unit via a real input signal to execute oscillations; the real output signal of the oscillatable unit is ascertained; the real output signal is digitized and a real output sequence is produced; the real input signal is digitized and a digital input sequence is produced; the digital input sequence is fed to a function block, which provides the mathematical model of the oscillatable unit in interaction with the medium. The mathematical model is defined by at least two sensor-specific variables; a virtual output sequence is produced via the mathematical model. The virtual output sequence is compared with the real output sequence; in the case of a deviation, the sensor-specific variables of the mathematical model are adaptively changed, until the deviation between the virtual output sequence and the real output sequence of the oscillatable unit lies within a predetermined tolerance range.

First claim

The invention claimed is:

1. A method for calibrating or adjustment of an oscillatable unit of a vibronic sensor with a mathematical model describing the oscillatable unit, the oscillatable unit interacts with a medium located in a container and is utilized for ascertaining or monitoring at least a limit level, a density, a viscosity or a temperature of said medium in automation technology, comprising the steps of:
exciting the oscillatable unit via a real input signal to execute oscillations;
ascertaining the real output signal of the oscillatable unit;
digitizing the real output signal and producing a real output sequence;
digitizing the real input signal and producing a digital input sequence;
feeding said digital input sequence to a function block, which provides the mathematical model of the oscillatable unit in interaction with the medium, said mathematical model being defined by at least two sensor-specific variables, wherein said sensor-specific variables are geometric parameters, material properties or mass ratios of the oscillatable unit;
producing a virtual output sequence via said mathematical model; and
comparing the virtual output sequence with the real output sequence;
wherein in the case of a deviation, the sensor-specific variables of said mathematical model are adaptively changed, until the deviation between the virtual output sequence and the real output sequence of the oscillatable unit lies within a predetermined tolerance range, and
wherein the oscillatable unit is associated with a sensor or a measuring device, which is used to determine fill level, density (ρ) or viscosity (η) of the medium in the container, and
wherein the sensor-specific variables or the geometric parameters (G1, G2) ascertained during the adjustment or the calibration are transmitted into a memory of the sensor, respectively of the measuring device.

2. The method as claimed in claim 1 , wherein:
the oscillatable unit is operated at an eigenfrequency.

3. The method as claimed in claim 1 , wherein:
the adjustment, respectively the calibration, of the oscillatable unit is performed in the medium under defined process-, respectively system specific, conditions.

4. The method as claimed in claim 3 , wherein:
during the adjustment or the calibration, the viscosity (η) and the density (ρ) of the medium are held constant and wherein the medium-contacting part of the oscillatable unit is in contact with the medium to a defined immersion depth.

5. The method as claimed in claim 1 , wherein:
the sensor-specific variables of the earlier adjusted, respectively calibrated, oscillatable unit are utilized in measurement operation of the sensor, respectively of the measuring device, for ascertaining process- and/or system specific parameters (ρ, η, T).

6. The method as claimed in claim 1 , wherein:
for ascertaining the sensor-specific variables, respectively the geometric parameters, and for ascertaining the process- and/or system specific parameters
(ρ, η, T), a description of the oscillatable unit in a state space or as transfer function is used as mathematical model, which describes the oscillatable unit as a linear or nonlinear system.

7. The method as claimed in claim 6 , wherein:
used as adaptation algorithm in the mathematical model for determining unknown parameters is a parameter estimation method, in which the oscillatable unit is described as a linear or nonlinear system and which describes the relationship between the input signal and the output signal by transfer functions or transfer matrices.

8. The method as claimed in claim 7 , wherein:
used as parameter estimation method for mathematical models in the form a transfer function is preferably the method of least squares, the generalized LS method, the RLS method, the method of auxiliary variables or the method of maximum probability.

9. The method as claimed in claim 6 , wherein:
used as parameter estimation method for mathematical models in state space is preferably the extended Kalman filter, the unscented Kalman filter or a subspace method.

Assignees

• Endress Hauser Gmbh Co Kg

Inventors

• Brengartner Tobias
• Bechtel Gerd
• D'Angelico Sascha

Classifications

• G01N9/00

  Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity · CPC title

• G01N2011/0006

  Calibrating, controlling or cleaning viscometers · CPC title

• G01N9/002

  using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis (G01N9/34 takes precedence) · CPC title

• G01N11/16

  by measuring damping effect upon oscillatory body · CPC title

• G01H3/005 Primary

  Testing or calibrating of detectors covered by the subgroups of G01H3/00 (calibrating geophysical instruments, e.g. seismic receivers G01V13/00) · CPC title