Quantifying Aspirated Bubbles via Pressure Signal Segmentation
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Solution Overview
Problem
Diagnostic analyzers face challenges in quantitatively measuring error-causing parameters, such as bubbles, during fluid handling processes due to confounding factors like pressure signatures from free surfaces and viscosity, making it difficult to accurately determine the volume of aspirated liquid.
Innovation Solution
A method that involves measuring pressure between a piston and liquid, detecting pressure abnormalities, determining the time of occurrence, and using calibration curves to quantify the magnitude of errors, allowing for the integration of flow rates to calculate the volume of errors like bubbles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure monitoring is used to detect air aspiration, then error detection capability is improved, but quantitative measurement precision deteriorates due to noise from free surface and vibration
Solution Approach 1:
The pressure signal is segmented into multiple parameters: mean pressure, pressure variation, rate of pressure change, and acceleration of pressure change. This segmentation allows the system to extract multiple features from the same pressure signal, enabling both error detection and quantitative measurement by analyzing different aspects of the segmented signal.
Solution Approach 2:
The invention transitions from analyzing pressure in one dimension to analyzing its derivatives in multiple dimensions (pressure, rate of change, acceleration). This dimensional expansion allows the system to distinguish between signal components caused by air aspiration versus those caused by free surface effects and vibration, thereby achieving quantitative measurement precision while maintaining error detection capability.
2Loss of information
If curve fitting with proper models is used to predict fluid properties, then useful information can be obtained, but the challenge of predicting error quantity remains due to system complexity
Solution Approach 1:
The invention introduces calibration curves as intermediary elements that link measurable pressure parameters to error quantities. These calibration curves serve as mediators between the complex physical system and the desired quantitative output, allowing the system to predict error quantities without directly modeling the complex fluid dynamics.
Solution Approach 2:
The invention changes the approach from modeling fluid properties directly to measuring and utilizing parameter changes (pressure, rate of pressure change, acceleration of pressure change) that occur during error events. By focusing on parameter changes rather than absolute values, the system simplifies the modeling complexity while still obtaining useful fluid property information.
3Ease of operation
If pressure level is used to represent aspirated liquid amount, then measurement is simplified, but accuracy deteriorates due to surface tension and meniscus configuration
Solution Approach 1:
The system performs preliminary calibration to establish the relationship between pressure parameters and actual liquid amounts under specific conditions. This preliminary action creates a reference framework that accounts for surface tension and meniscus effects, allowing subsequent measurements to be accurate without repeatedly considering these complex factors during operation.
Solution Approach 2:
The invention replaces direct mechanical measurement of liquid amount with pressure-based measurement. By using pressure sensors and analyzing pressure signal characteristics, the system substitutes a simpler mechanical measurement approach while achieving accurate liquid amount determination through signal processing and calibration.
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
Enables precise measurement of error volumes, enabling adjustments in analysis protocols and reducing the need for re-running assays by accurately determining the amount of liquid handled, thereby improving the reliability of fluid handling systems.
Implementation Method 1
a pressure sensor, such as a transducer, is mounted between the piston pump and the liquid being aspirated, and the pressure variation in the aspiration process is monitored
Data Source
AI summary
A method for quantitatively measuring error causing physical parameters in a fluid handling system, includes: measuring the pressure of air between a piston of a pump and a liquid being handled; detecting a pressure abnormality; determining the time at which the pressure abnormality begins to occur; and based on the time of the pressure abnormality determining the magnitude of the physical parameter causing the pressure abnormality. In a preferred embodiment, the error causing physical parameter is a bubble and the fluid handling is an aspirate operation in a diagnostic analyzer.