Coriolis Flow Meter Three Contactless Sensors
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Solution Overview
Problem
Existing Coriolis mass flowmeters face sensitivity drift due to non-constant sensor positions relative to the axis of rotation, affecting accuracy in measuring low flow rates, as the sensors are not mechanically connected to the tube and can be influenced by temperature, pressure, and gravity changes.
Innovation Solution
A Coriolis flowmeter using three contactless sensors that measure time information to determine the ratio of excitation and Coriolis-induced movements, allowing for accurate mass flow computation independent of the pole of rotation's location, with algorithms in digital circuits compensating for any shifts in the pole's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contactless sensors are used to measure tube movement, then the tube can be moved by very low forces enabling measurement of low mass flows, but the sensor positions relative to the axis of rotation are not constant causing sensitivity drift
Solution Approach 1:
The patent uses feedback by continuously monitoring the positions of multiple sensors and using this information to dynamically adjust measurements. The sensor position data is fed back to the evaluation unit, which compensates for position variations in real-time, maintaining measurement accuracy despite thermal expansion or mechanical drift.
Solution Approach 2:
The patent replaces mechanical connection between sensors and tube with contactless optical or capacitive sensing. This substitution eliminates mechanical constraints that would otherwise fix sensor positions, allowing flexible mounting while maintaining measurement capability through field-based detection.
2Reliability
If sensors are mechanically joined to the tube, then sensor positions remain constant improving sensitivity stability, but the tube cannot be moved by very low forces reducing ability to measure low mass flows
Solution Approach 1:
The patent replaces mechanical joining of sensors to the tube with contactless sensing fields (optical or capacitive). This allows the tube to move freely under minimal force while sensor positions are tracked and compensated for electronically, achieving both low-force measurement capability and position stability.
Solution Approach 2:
The patent changes the measurement parameter from fixed mechanical position to dynamically tracked position. By continuously monitoring sensor positions and using this data for compensation, the system maintains measurement accuracy despite position variations, effectively treating position as a variable parameter rather than a fixed constraint.
3Device complexity
If only two sensors are used, then the device complexity is reduced, but the ability to compensate for pole of rotation shifts is insufficient reducing measurement accuracy
Solution Approach 1:
The patent segments the measurement function across multiple sensors positioned at different locations. Each sensor provides independent position data, and the evaluation unit integrates this segmented information to calculate the pole of rotation position and compensate for shifts, achieving higher accuracy through distributed measurement.
Solution Approach 2:
The patent adds spatial dimensionality by positioning sensors at different radial distances from the axis of rotation. This multi-dimensional sensor arrangement enables determination of the pole of rotation position and provides redundancy for compensation, transforming a one-dimensional measurement problem into a multi-dimensional solution.
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 enhances sensitivity and accuracy by using time information from all three sensors to determine the amplitude ratio, enabling precise mass flow measurement even with shifts in the pole of rotation, thus improving the instrument's performance in measuring low flow rates.
Implementation Method 1
The Coriolis principle is based on the effect that a mass flow displacing in a rotating plane generates a force perpendicular to the direction of movement of the mass flow and the axis of rotation
Implementation Method 2
three optical sensors a, b, and c arranged in line and associated with the tube for generating analog signals in three positions in correspondence with the movement of the tube
Data Source
Figure 1
Figure 2~3
AI summary
A flow measuring system of the Coriolis type for measuring a mass flow, with a flow tube and with excitation means for causing the flow tube to rotate about an axis of rotation, with at least three sensors arranged free of the flow tube for generating analog signals that correspond to the movement of the tube, and with means for digitizing the analog signals and for computing the mass flow from the digitized sensor signals. The computation means are arranged for using exclusively the time information from the sensor signals. The accurate time information of the sensors is used by algorithms in digital electronic circuits for accurately determining the ratio between amplitudes due to excitation and those due to Coriolis forces. The mass flow is derived from this ratio.