Aperture Blockage Detection in Particle Counters
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Solution Overview
Problem
Current methods for detecting aperture blockage in Coulter Counter-type particle characterization devices are unreliable, particularly in detecting partial blockages and distinguishing them from other voltage changes, often requiring user intervention and visual monitoring.
Innovation Solution
A particle characterization device that automatically detects aperture blockage by monitoring multiple parameters such as flow rate, aperture resistance, and pulse concentration, allowing for preselected threshold values to be set, and taking predetermined actions when blockages are detected, thereby reducing the need for user intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If visual monitoring methods (magnified window or CCD image) are used to detect aperture blockage, then blockage can be identified, but user intervention is required and it is difficult to maintain optical focus and reliably detect partial blockages
Solution Approach 1:
The patent replaces optical detection methods (magnified window or CCD imaging) with an electronic detection system that measures electrical resistance across the aperture. This substitution eliminates the need for visual monitoring and optical focus maintenance, providing automated, reliable detection of both complete and partial blockages through electrical parameter changes.
Solution Approach 2:
The system enables automated blockage detection and identification without requiring continuous user monitoring or intervention. The electronic resistance measurement system operates autonomously to detect blockage conditions, allowing the particle characterization run to proceed with minimal user involvement while maintaining reliable blockage identification.
2Reliability
If a single parameter (voltage pulse width) is monitored for blockage detection, then some blockages can be detected, but partial blockages and transient blockages are difficult to distinguish from other factors
Solution Approach 1:
The patent segments the blockage detection process into multiple independent parameter measurements: voltage pulse width, steady-state resistance, flow rate, and count rate. Each parameter provides distinct information about blockage conditions, allowing the system to differentiate between complete blockages, partial blockages, and transient blockages by analyzing the pattern of changes across multiple parameters rather than relying on a single measurement.
Solution Approach 2:
The patent adds another dimension to blockage detection by introducing steady-state resistance measurement in addition to voltage pulse width monitoring. This additional measurement dimension enables the system to distinguish blockage events from other factors affecting aperture voltage, as blockages produce characteristic changes in both pulse width and steady-state resistance that differ from other phenomena.
3Measurement precision
If the aperture size is made small to ensure particles pass through one at a time, then particle characterization accuracy is improved, but the aperture becomes more susceptible to blockage by larger particles or aggregates
Solution Approach 1:
The patent implements a feedback system that continuously monitors multiple parameters (voltage pulse width, steady-state resistance, flow rate, count rate) to detect aperture blockage conditions. When blockage is detected, the system can alert the user or automatically take corrective action, allowing the run to be resumed after blockage removal. This feedback mechanism compensates for the increased blockage susceptibility of smaller apertures by enabling rapid detection and response to blockage events.
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
The solution provides a more reliable detection of both partial and complete blockages, reduces false positives, and allows for unattended operation by automatically addressing blockages during a run, ensuring continuous analysis without manual intervention.
Implementation Method 1
A pair of electrodes connected to a power source and disposed across the aperture, one in each chamber, provides a voltage difference across the aperture. Electrolytes in the liquid move from one chamber to the other in response to the applied voltage, generating an electric current.
Implementation Method 2
Entry of a particle into the aperture displaces some of the charged electrolyte in the aperture, causing an increased electrical resistance across the aperture, resulting in an increased voltage measured across the aperture when current is held constant.
Data Source
AI summary
An apparatus for characterizing particles suspended in a liquid sample containing electrolyte including a sample chamber to hold the liquid sample and a collection chamber to hold an electrolyte solution. A wall separates the chambers and includes an aperture to allow passage of particles between the chambers; and a pair of electrodes are disposed on opposite sides of the aperture to induce a current through the aperture. A pressure source forces the sample to pass from the sample chamber into the collection chamber; and a processor measures a signal representative of electric resistance variation between the electrodes to enable determination of the size of the particle within the liquid passing through the aperture, wherein the processor is adapted to monitor two or more parameters characterizing the flow of particles through the aperture, and to detect a potential blockage of the aperture by detecting a change in any one of the parameters.