Oscillating Unit Frequency Sweep for Vibronic Sensor Accuracy
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Solution Overview
Problem
Existing methods for determining measurement frequencies in vibronic devices are limited by short time frames for frequency sweeps, leading to superimposition effects that result in inaccurate determination of phase shifts and measurement frequencies.
Innovation Solution
A method involving two frequency searches within a predetermined frequency band, one in increasing and one in decreasing order, with identical parameters, to determine the measurement frequency by averaging the first and second excitation frequencies, thereby compensating for amplitude and phase errors and allowing for quick and accurate determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a frequency sweep is performed quickly to determine measurement frequency, then the time available for the oscillating system to adjust is reduced, but this leads to superimposition effects and inaccurate phase shift determination
Solution Approach 1:
The frequency sweep is divided into two separate sweeps: an upward sweep from lower to higher frequencies and a downward sweep from higher to lower frequencies. Each sweep independently determines an excitation frequency, and the final measurement frequency is calculated as the average of these two frequencies. This segmentation eliminates superimposition effects that occur in single rapid sweeps, providing accurate results even with limited time.
Solution Approach 2:
Instead of performing a single frequency sweep in one direction, the method performs sweeps in opposite directions (upward and downward). This inversion approach ensures that the oscillating system has sufficient adjustment time in each direction while maintaining quick overall measurement, thereby resolving the contradiction between speed and accuracy.
2Productivity
If the frequency band is run through quickly with a constant number of excited frequencies, then the measurement time is reduced, but superimposition effects occur leading to incorrect measurement frequency
Solution Approach 1:
The measurement process is segmented into two distinct frequency sweeps performed in opposite directions. Each sweep independently excites the oscillating system at multiple frequencies, allowing the system to adjust properly without superimposition effects. The final result is derived by averaging the excitation frequencies from both sweeps, maintaining both speed and reliability.
Solution Approach 2:
The direction of the frequency sweep is changed between the two measurements (upward vs. downward). This parameter change in sweep direction, combined with averaging the results, compensates for dynamic properties of the sensor and eliminates systematic errors, thereby maintaining high reliability while preserving measurement speed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables reliable and accurate determination of measurement frequencies independent of time constraints, reducing errors and component demands, and is applicable to various vibronic devices for measuring level, density, viscosity, and flow.
Implementation Method 1
Mechanical vibrations are usually stimulated by means of a piezoelectric drive, in which at least one piezoelectric element coupled to the oscillatable unit is subjected to an electrical transmission signal, which converts it into a mechanical signal. Conversely, the mechanical vibrations of the oscillatable unit can be converted into analyzable electrical signals by means of a piezoelectric receiving unit.
Implementation Method 2
The oscillatable unit is excited to resonant oscillations and a change in the oscillation frequency and/or the amplitude of the oscillations and/or the phase between the transmitted signal and the received signal in relation to the process variable, primarily a limit fill level or the density of the measuring medium, is evaluated.
Implementation Method 3
The flow rate can be determined via the Coriolis effect. However, statements about the density and viscosity of the medium can also be derived from the vibration behavior.
Data Source
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AI summary
Method for operating an apparatus for determining and/or monitoring at least one physical process variable for a medium having an oscillating unit (2), wherein the oscillating unit is prompted to oscillate by means of a first frequency search process within a predetermined frequency band in the operating range of the oscillating unit at successive discrete excitation frequencies of rising or falling frequency, wherein the relevant oscillations in the oscillating unit are received and wherein a first excitation frequency (f1) is ascertained for which, during the first frequency search process, at least one prescribable criterion is satisfied, wherein the oscillating unit is prompted by means of a second frequency search process, wherein the frequency band is swept in the opposite direction in comparison with the first frequency search process, wherein a second excitation frequency (f2) is ascertained for which, during the second frequency search process, the at least one prescribable criterion is satisfied, and wherein a measurement frequency (fm) for determining and/or monitoring at least one process variable is determined from the first excitation frequency (f1) and the second excitation frequency (f2) by means of averaging.