Optical Coriolis Flowmeter Circuit for Low-Phase-Error Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Coriolis flowmeters using optical detection devices often suffer from accuracy issues due to parasitic capacitance and temperature-dependent time constants, leading to phase rotation and reduced measuring accuracy.
Innovation Solution
The implementation of a transimpedance amplifier with a low input impedance to maintain a constant voltage across the photosensitive sensor, reducing parasitic capacitance effects and using a differential amplifier to eliminate voltage offset, thereby improving signal quality and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high resistance value is chosen for the photosensor to generate a high voltage signal, then the voltage signal amplitude is improved, but the time constant increases causing phase rotation and measurement error
Solution Approach 1:
The patent changes the electrical parameters of the photosensor circuit by applying a constant voltage independently of the sensor current, transforming the traditional current-to-voltage conversion approach into a voltage-controlled approach that decouples the time constant from the signal amplitude.
Solution Approach 2:
The patent replaces the passive resistive voltage generation mechanism with an active electronic circuit (constant voltage source with current determination), substituting the physical RC time constant limitation with an electronic solution that can maintain both high signal amplitude and low time constant.
2Measurement precision
If the parasitic capacitance is compensated for once and for all through calibration, then the initial accuracy is improved, but temperature drift and aging cause significant measuring errors over time
Solution Approach 1:
The patent transitions from a static calibration approach to a dynamic constant voltage approach that actively maintains the photosensor operating conditions. The constant voltage source continuously compensates for drift effects by maintaining stable voltage across the sensor regardless of capacitance changes due to temperature or aging.
Solution Approach 2:
The patent implements a feedback mechanism where the electronic circuit continuously monitors and adjusts to maintain constant voltage across the photosensor, automatically compensating for drift effects without requiring recalibration. The circuit adapts to changing conditions by maintaining the voltage parameter constant.
3Measurement precision
If a transimpedance amplifier with low input impedance is used to maintain constant voltage across the photosensitive sensor, then phase rotation is reduced and accuracy is improved, but device complexity increases
Solution Approach 1:
The patent introduces a transimpedance amplifier as an intermediary device between the photosensor and the signal processing circuitry. This intermediary component provides the constant voltage condition while isolating the sensor from direct loading effects, simplifying the overall design compared to more complex active compensation circuits.
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 phase rotation and maximizes the resolution of the flowmeter by maintaining a constant voltage and eliminating voltage offset, enhancing the accuracy and reliability of the flow measurement.
Implementation Method 1
The optical sensor comprises a light source and a photosensitive sensor... The light sensor acts as a photon counter, the current through the sensor being proportional to the quantity of incident light
Implementation Method 2
the means for applying a constant voltage across the photosensitive sensor during operation independently of the current generated by the photosensitive sensor... A preferred embodiment is characterized in that the means for applying a constant voltage across the photosensitive sensor during operation comprise a transimpedance amplifier
Implementation Method 3
a Coriolis tube... wherein the Coriolis tube or a projection fastened to the Coriolis tube moves through the light path between the light source and the photosensitive sensor during operation
Data Source
AI summary
Coriolis mass flowmeter with a Coriolis tube and with an optical detection device, which optical detection device comprises at least one optical sensor for generating a signal that is representative of the movement of the Coriolis tube, said optical sensor comprising a light source and a photosensitive sensor, wherein the optical detection device comprises means for applying a constant voltage across the photosensitive sensor during operation independently of the current generated by the photosensitive sensor in response to incident light, as well as means for determining the value of the current generated by the photosensitive sensor and converting it into an output signal.