Density Measuring Device Phase Control Vibration
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Solution Overview
Problem
Conventional vibronic density measuring devices have accuracy issues due to dependence on damping and viscosity of the medium, leading to significant deviations in density measurements.
Innovation Solution
The device excites mechanical vibrations at a frequency offset from the resonance frequency, maintaining a phase shift angle between -30° and -70° to minimize dependence on damping and viscosity, allowing for accurate density measurement without resonance conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional vibronic density measuring devices use resonance vibrations for measurement, then the measurement process is simple and efficient, but the measurement accuracy deteriorates due to dependence on damping and viscosity
Solution Approach 1:
The patent changes the operating parameter from resonance frequency to a frequency offset from resonance, specifically maintaining a phase shift angle between -30° and -70°. This parameter change eliminates the dependence on damping and viscosity that plagues resonance-based measurements, thereby improving density measurement accuracy without requiring fundamental changes to the device structure
Solution Approach 2:
The patent utilizes mechanical vibrations of the measuring tube but operates them outside the resonance condition. By exciting the measuring tube at a frequency that produces a controlled phase shift between velocity response and driving force, the system achieves accurate density measurements that are independent of the medium's damping and viscosity characteristics
2Measurement precision
If the measuring tube is excited at resonance frequency, then the vibration amplitude is maximized for easy detection, but the measurement accuracy deteriorates due to viscosity dependence
Solution Approach 1:
The patent optimizes the operating frequency parameter to be offset from resonance by a specific phase shift angle (-30° to -70°). This optimization achieves a balance where sufficient vibration amplitude is maintained for detection while eliminating the harmful dependence on viscosity and damping, thereby improving measurement accuracy
3Ease of operation
If resonance vibrations are used for density measurement, then the measurement process is straightforward, but significant deviations occur due to damping and viscosity effects
Solution Approach 1:
The patent employs feedback control to maintain the phase shift angle between the velocity response and driving force within the optimal range of -30° to -70°. The measuring electronics continuously monitor the vibration characteristics and adjust the excitation frequency to maintain the desired phase relationship, ensuring accurate measurements while keeping the operation automated and straightforward
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 approach significantly reduces the impact of damping and viscosity on measurement accuracy, enabling high precision density measurements with maintained vibration amplitude and frequency control.
Implementation Method 1
a vibration exciter (41) which serves to convert electrical excitation power into a driving force causing useful vibrations of the at least one measuring tube (10)
Implementation Method 2
the at least one measuring tube (10) performs useful vibrations, namely mechanical vibrations around a rest position with a useful frequency that is also determined by the density of the medium
Implementation Method 3
a phase shift angle (φN) between the velocity response and the useful force component of the driving force (FN)
Data Source
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AI summary
The invention relates to a density measuring device which is used to measure a density, ρ, of a flowable medium and comprises measuring-device electronics (ME) and a measuring transducer (MW) electrically connected to the measuring-device electronics. The measuring transducer comprises a measuring tube (10), a vibration exciter (41) for exciting and maintaining vibrations, and a vibration sensor (51) for sensing vibrations of the at least one measuring tube. The measuring device electronics are designed to adjust, by means of a vibration measurement signal (s1) and an exciter signal (e1), a driving force that causes useful vibrations, namely vibrations having a specified useful frequency, fN, of the measuring tube, in such a way that a phase shift angle, φΝ, by which a velocity response, VN, of the measuring tube is phase-shifted with respect to a useful force component, FN, of the driving force is less than -20° and greater than -80° during a specified phase control interval, and/or the useful frequency has a frequency value that is more than 1.00001-times but less than 1.001-times a frequency value of an instantaneous resonance frequency of the measuring tube. Furthermore, the measuring device electronics are designed both to determine at least one frequency measured value, Xf, representing the useful frequency for said phase control interval on the basis of the vibration measurement signal (s1) present during the phase control interval and to generate a density measured value, Xρ, representing the density, ρ, by using the frequency measured value, Xf.