Particle Counter Threshold Adjustment Circuit
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Solution Overview
Problem
Current particle counting methods in flow cytometry face resolution limitations and increased uncertainty due to coincidences of multiple events, leading to sensor saturation and inaccurate measurements, especially when counting high numbers of particles.
Innovation Solution
A particle counting device with a mobile threshold adjustment circuit that applies a low-pass filter to the measurement signal, allowing the detection threshold to increase with the signal strength, thereby improving resolution and reducing lost counts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed threshold is used for particle detection, then the device is simple to operate, but resolution deteriorates when counting large numbers of particles due to coincidences
Solution Approach 1:
The patent applies a low-pass filter to the measurement signal to generate a dynamic threshold that automatically adapts to the event rate. The threshold is no longer fixed but varies with the signal characteristics, allowing the system to maintain resolution during high-event-rate conditions without requiring manual adjustment or complex external control systems.
2Reliability
If the detection threshold is increased to reduce noise, then false detections are reduced, but legitimate particle events are missed
Solution Approach 1:
The patent uses the measurement signal itself as feedback to dynamically adjust the threshold. The low-pass filtered measurement signal continuously informs the threshold level, creating a closed-loop system where the threshold adapts to actual signal conditions rather than being set statically, thereby maintaining optimal detection sensitivity across varying event rates.
3Measurement precision
If linearization methods are used to correct coincidence errors, then counting accuracy is improved, but device complexity and calibration requirements increase
Solution Approach 1:
The patent prevents coincidence errors by dynamically adjusting the threshold in advance based on the low-pass filtered signal, rather than attempting to correct errors after they occur. This proactive approach avoids the need for complex post-processing linearization algorithms and calibration procedures, maintaining accuracy while keeping the system simple.
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 enhances the device's ability to accurately count particles by maintaining resolution and reducing measurement uncertainty, even in high-event scenarios, by dynamically adjusting the detection threshold in response to the measurement signal.
Implementation Method 1
a threshold adjustment circuit that applies a low-pass filter to the measurement signal
Implementation Method 2
measuring the change in impedance within a measurement zone as one or more particles are guided through it in flow, known as the Coulter method
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a device for counting particles, comprising a detector arranged to produce an electrical measurement signal in response to the passage of one or more particles, and a comparator arranged to compare the measurement signal with a threshold signal and to increase a count value when the measurement signal exceeds the threshold signal. The device is characterised in that it also comprises a threshold adjustment circuit which applies a low pass filter to the measurement signal and which is connected to the comparator in order to use the resulting signal as a threshold signal.