Multi-Sensor Mass Flow Meter for Diffusion Error Correction
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Solution Overview
Problem
Prior art Time-Of-Flight mass flow meters face inaccuracies due to diffusion errors at low flows, inability to differentiate between zero flow and air bubbles, and sensitivity to sharp flow variations, leading to unreliable measurements, especially in medical and industrial applications.
Innovation Solution
The implementation of a mass flow metering system with multiple sensors along the flow conduit, utilizing at least three time events to calculate flow rates and incorporating additional sensors for diffusion correction, positive zero flow detection, and air bubble detection, along with a method to analyze the shape and intensity of the mark to determine fluid properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple detectors are spaced downstream from the thermal marking position to overcome fluid properties affects, then measurement accuracy is improved, but device complexity and cost increase prohibitively
Solution Approach 1:
The flow meter is divided into multiple sensing zones along the flow conduit, with each zone having its own detector. This segmentation allows the system to capture flow characteristics at different positions without requiring a single complex detector, thereby improving measurement accuracy while managing device complexity through modular design
Solution Approach 2:
The detectors are designed to serve multiple functions: they detect the thermal mark, measure flow velocity, and provide data for calculating both instantaneous and average flow rates. This multi-functionality reduces the need for separate specialized components, lowering overall device complexity while maintaining high measurement precision
2Device complexity
If Miller's approach uses two time events to derive flow rate, then the system remains simple, but it cannot extract additional information needed for accurate flow rate determination under varying flow conditions
Solution Approach 1:
The system performs preliminary measurements of multiple time events (t1, t2, t3) before final flow rate calculation. By collecting this additional temporal data in advance, the system prepares comprehensive information needed to accurately determine flow rates under varying conditions, including stable, accelerating, and decelerating flow states
Solution Approach 2:
The system uses feedback from multiple time event measurements to continuously refine flow rate calculations. The processor analyzes the relationships between t1, t2, and t3 to detect flow regime changes and adjusts calculations accordingly, providing accurate measurements even when flow conditions change during the measurement cycle
3Reliability
If thermal pulse technique is used with unheated fluid reference, then the system is insensitive to ambient temperature changes, but measurement error occurs due to heat transfer to and from the fluid
Solution Approach 1:
The unheated fluid acts as an intermediary reference medium. By introducing a thermal mark into the fluid and using unheated fluid as reference, the system can measure flow velocity while being insensitive to ambient temperature changes. The unheated fluid provides a stable baseline against which thermal mark propagation can be measured, isolating the measurement from external temperature variations
Solution Approach 2:
The system changes the thermal parameters of the fluid by introducing a heated mark that creates a temporary temperature difference. This parameter change allows the system to measure flow velocity through thermal propagation while the unheated reference fluid maintains insensitivity to ambient temperature, effectively decoupling measurement accuracy from environmental conditions
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 the accuracy of flow rate measurements by correcting for diffusion and viscosity effects, providing reliable detection of zero flow and air bubbles, and improving the dynamic range of the meter, thus reducing errors and ensuring safer and more precise fluid flow monitoring.
Implementation Method 1
Each pulse, comprising a small fluid volume, whose composition is different from the mean composition of the fluid, can be created by electrochemical means... Measurements of the conductivity of the fluid can be used to detect the arrival time of the pulses, from which the fluid flow rate can be determined
Implementation Method 2
the transient time it takes the mark to integrate into the developed flow profile... the rate of equilibration is associated with the thermal masses, thermal conductivities, heat-transfer coefficients of the heating element, sensor and fluid, and the viscosity and density of the fluid
Implementation Method 3
Measurements of the conductivity of the fluid can be used to detect the arrival time of the pulses... A pair of spaced apart electrodes can be used to produce the electrochemical pulse mark
Data Source
AI summary
A device for measuring fluid flow rates over a wide range of flow rates. The invention is particularly adapted for use in micro-fluidic systems including fluids administration to a body of a patient. The device operates by producing characteristics variations in the fluid, or pulses, that are subsequently sensed by more than one detector spaced apart from the point of creation of the mark to derive a flow rate. Each pulse comprises a small fluid volume, whose characteristics are different from the mean characteristics of the fluid, such as by composition variations created by electrochemical means, such as by electrolysis of a solvent, electrolysis of a dissolved species, or electrodialysis of a dissolved ionic species, or a thermal variation created by focused electromagnetic radiation. The device comprises at least two detectors (also sometimes referred to as sensors) to improve the accuracy of the measurement in varying flow rates, to compensate for errors resulting from the drift of the pulses in the fluid, to compensate for varying or unstable flow rates, and to establish a positive signal for sub-range flow. A method of measuring fluid flow rate is proposed where measurements comprising data of one mark from at least two sensor readings plus one other time event are combined to determine the reported flow rate.