Fluid Level Detection Using Frequency-Energized Sample
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Solution Overview
Problem
Conventional level detection systems in immunoassay analyzers with septum or foil seal closures are unreliable in determining the sample surface location, leading to contamination and incorrect aspiration due to high false positive rates.
Innovation Solution
A level sense system that energizes the sample and container with a specific frequency, using a bandpass filter and comparator to distinguish the fluid sample surface from other container surfaces, ensuring accurate detection by comparing output signals to threshold levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive level sense techniques are used to detect sample surface contact, then the system can identify when the pipette reaches the sample surface, but the technique produces a high rate of false positives by responding to any surface with a signal present
Solution Approach 1:
The patent applies local quality by energizing only the sample fluid and container at a specific frequency, creating a localized electromagnetic field that is confined to the sample region. The bandpass filter is tuned to this specific frequency to detect signals only from the energized sample, distinguishing it from other container surfaces that do not resonate at this frequency, thereby eliminating false positives from non-sample surfaces
Solution Approach 2:
The system performs preliminary action by pre-energizing the sample and container with a specific frequency signal before pipette insertion. This preliminary energizing creates a known electromagnetic signature at the sample surface, allowing the level sense circuit to reliably detect when the pipette contacts the sample by monitoring for this pre-established signal pattern, rather than relying on passive capacitive sensing that responds to all surfaces
2Productivity
If the pipette is driven down into the sample a set distance to reach the bottom of the container, then the pipette can retrieve sample material, but this coats the pipette with sample material that needs to be washed away to prevent contamination
Solution Approach 1:
The system performs preliminary action by detecting the sample surface level before pipette insertion using the energized level sense circuit. This preliminary detection allows the system to calculate the precise insertion depth needed to reach the sample surface, enabling the pipette to aspirate sample without driving to the container bottom, thereby preventing excessive sample coating and contamination
Solution Approach 2:
The patent replaces the mechanical approach of driving the pipette a fixed set distance with an electronic control system that uses electromagnetic sensing to dynamically determine insertion depth. The level sense circuit provides real-time feedback on sample surface location, allowing the system to substitute mechanical trial-and-error insertion with precision electronic control based on detected signal levels
3Productivity
If the pipette is moved a set amount to reach the sample, then sample aspiration can be performed, but the possibility of aspirating an empty container or driving the pipette through the container is not reliably mitigated
Solution Approach 1:
The system performs preliminary action by using the level sense circuit to detect the presence and location of the sample surface before initiating pipette aspiration. This preliminary detection confirms that sample is present in the container and determines the correct insertion depth, preventing the pipette from aspirating air in empty containers or being driven through the container bottom
Solution Approach 2:
The patent implements feedback by continuously monitoring the electromagnetic signal from the energized sample during pipette insertion. The level sense circuit provides real-time feedback on the pipette's position relative to the sample surface, allowing the system to adjust insertion depth dynamically and stop aspiration when the sample surface is reached, preventing over-insertion and container damage
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
Minimizes pipette insertion depth, reduces contamination, and prevents aspiration of air or empty containers by accurately identifying the sample surface, thereby improving operational efficiency and reducing cleanup needs.
Implementation Method 1
A level sense system that energizes the sample and container with a specific frequency, using a bandpass filter and comparator to distinguish the fluid sample surface from other container surfaces
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
A fluid level detecting system provides an input signal at a specific frequency to a sample in a container. A probe contacts the energized sample and provides a signal to a level sensing circuit. The level sensing circuit amplifies the signal from the probe and then bandpass filters, tuned to the specific frequency, the amplified signal. This filters out extraneous signals received from, for example, a cover on the container, and specifically identifies when the probe has contacted the sample fluid by comparing the filtered signal to threshold levels.