Digital Pulse Midpoint Sizing for Aperture Particle Measurement
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Solution Overview
Problem
Conventional particle size measurement systems, such as Coulter Principle-based systems, face challenges in accurately measuring particle size due to non-axial trajectories of particles through detection apertures, leading to variable pulse peak values and inefficiencies in pulse editing techniques, which result in inaccurate histograms and increased time to build up particle size distributions.
Innovation Solution
The system digitizes pulses produced by aperture measurement circuitry and processes them through pipelined digital processing circuitry, continuously sampling and storing data to locate pulse width at prescribed percentages of the peak amplitude, determining pulse amplitude at the midpoint of the pulse width between rising and falling edges, using analog-to-digital conversion, pulse threshold comparators, and logic circuitry to identify and process peak and duration data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse editing techniques are used to discard undesirable pulses, then measurement accuracy is improved, but productivity decreases due to loss of captured events and increased time to build histograms
Solution Approach 1:
The invention changes the measurement parameter from peak amplitude to mid-point amplitude (amplitude at 50% of pulse width). This parameter change allows accurate particle size measurement without discarding pulses, as the mid-point amplitude is less sensitive to trajectory variations. The system calculates the pulse width at 50% peak amplitude, finds the mid-point of the pulse, and uses the amplitude at that mid-point location for sizing, thereby maintaining both accuracy and throughput.
2Measurement precision
If analog integration and delay lines are used to find mid-flight point, then measurement accuracy is improved, but device complexity increases and manufacturing becomes difficult
Solution Approach 1:
The invention replaces the mechanical/analog system (integration and delay lines) with a digital signal processing system. The digital system samples the pulse waveform, stores samples in memory, and uses digital logic to calculate pulse width and identify the mid-point. This substitution eliminates the need for precise analog components and tolerance matching, significantly reducing device complexity and improving manufacturability while maintaining measurement accuracy.
3Measurement precision
If fixed delays and circuit state overhead are used in analog systems, then mid-flight point can be found, but productivity decreases due to limited throughput
Solution Approach 1:
The invention uses dynamic digital processing that adapts to each pulse waveform. Instead of fixed delays, the system calculates the actual pulse width for each pulse and determines the mid-point dynamically. The digital processing pipeline can handle multiple pulses in parallel, with no dead time between measurements, thereby maximizing throughput while maintaining accurate mid-flight point detection for each individual pulse.
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 allows for accurate and efficient measurement of particle size without editing, reducing the time to build up particle size distributions and minimizing the loss of captured events, while handling noise pulses effectively, thus improving the accuracy and throughput of particle size analysis.
Implementation Method 1
An analog-to-digital (A-D) converter installed at the front end of the system is continuously sampling the output of the flow cell's aperture monitoring circuitry
Data Source
AI summary
Pipelined digital processing circuitry for use with a particle size measurement system, such as that employed in automated hematology systems, measures the ‘center’ amplitude of a pulse produced by a particle or cell passing through a flow cell measurement aperture, such as the detection aperture of a Coulter Principle-based electronic particle analysis system. The circuitry of the invention processes successive pulse samples by means of a half-peak/half-width methodology that analyzes each pulse as its continuously sampled and temporarily stored in memory. Concurrent analysis of the data in memory during storage locates the pulse width at a prescribed percentage (e.g., 50%) of the peak amplitude of the pulse. This pulse width data is then processed to determine the pulse amplitude at the midpoint of the width of the pulse between its mid-peak values on rising edge and fall edge portions of the pulse.