Liquid Aspiration Needle Capacitance Detection
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Solution Overview
Problem
Current liquid surface detection methods in sample analyzers are susceptible to interference, leading to a high false detection rate due to changes in the dielectric environment, such as static electricity, bubbles, and liquid films, which can result in inaccurate aspiration of liquids.
Innovation Solution
A sample analyzer with a liquid aspiration control method that acquires and analyzes electrical signals during the aspiration process, meeting multiple preset conditions to confirm the presence of the liquid surface, thereby reducing false positives and ensuring accurate detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single electrical signal threshold is used for liquid surface detection, then the detection speed is fast, but the false detection rate increases due to interference from dielectric changes
Solution Approach 1:
The patent segments the liquid surface detection process into multiple stages: a first detection stage using a first electrical signal threshold, and a second detection stage using a second electrical signal threshold. This segmentation allows the system to use different detection strategies at different times, reducing false detections while maintaining overall detection speed.
Solution Approach 2:
The patent implements preliminary action by performing a first liquid surface detection before the main detection process. This preliminary detection identifies potential false alarm scenarios, allowing the system to adjust its detection strategy accordingly and prevent false positives in subsequent detection stages.
2Reliability
If multiple detection conditions are applied to reduce false positives, then the detection accuracy improves, but the detection time increases
Solution Approach 1:
The patent applies dynamics by making the detection process adaptive rather than static. The system dynamically switches between different detection modes: using the first electrical signal threshold under normal conditions for fast detection, and switching to the second electrical signal threshold when interference is detected. This dynamic adaptation maintains high detection accuracy while minimizing detection time.
Solution Approach 2:
The patent implements local quality by applying different detection thresholds to different detection scenarios. The first electrical signal threshold is used for general detection scenarios where speed is priority, while the second electrical signal threshold is applied locally to specific scenarios where false detection risk is identified, optimizing the balance between speed and accuracy for each local condition.
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 method improves the accuracy of liquid surface detection by sending confirmation only when the electrical signal meets specific preset conditions, preventing false reporting and ensuring the liquid aspiration needle reaches the correct depth without bumping into the container bottom.
Implementation Method 1
a capacitive detection method is a mainstream liquid surface detection method in the industry... a liquid aspiration needle is equivalent to a positive plate of a capacitor... a capacitance change will cause an electrical signal change
Implementation Method 2
before the liquid aspiration needle is in contact with the liquid surface, a container, a liquid to be detected, air, a sample rack, and some interferents all act as the dielectric of the capacitor... the dielectric of the capacitor changes, which will cause the capacitance change
Data Source
AI summary
The embodiments of the disclosure provide a sample analyzer and a liquid aspiration control method for a sample analyzer. When a liquid aspiration assembly is moving down toward a container, a signal acquisition and analysis assembly acquires and analyzes a first electrical signal; when the first electrical signal meets a first preset condition, the signal acquisition and analysis assembly acquires and analyzes a second electrical signal that is an electrical signal subsequent to the first electrical signal, and determines, according to at least the second electrical signal, whether the second electrical signal meets a second preset condition different from the first preset condition; and when the second electrical signal meets the second preset condition, the signal acquisition and analysis assembly sends information indicating that the liquid aspiration assembly reaches a surface of the liquid. The accuracy of liquid surface detection of the liquid in the container is improved by sending the information indicating that the liquid aspiration assembly reaches a surface of the liquid only when the electrical signal acquired by the signal acquisition and analysis assembly meets the first preset condition and the second preset condition.