Automatic Analyzer Electrostatic Probe Sensing for Variable Sample Levels
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Solution Overview
Problem
Existing automatic analyzers face inaccuracies in sample and reagent dispensing due to deviations in threshold voltage calculations when the sample or reagent does not reach the maximum capacity of the container, leading to potential errors in liquid surface sensing.
Innovation Solution
An automatic analyzer equipped with a liquid surface height detection device and a dispensing control unit that adjusts the dispensing probe's operation based on the actual liquid surface height, using electrostatic capacity to generate a liquid surface sensing signal and set thresholds accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the threshold voltage is calculated on the assumption that the sample is accommodated up to the maximum height of the sample container, then the dispensing control is simplified, but the liquid surface sensing accuracy deteriorates when the sample does not reach the maximum capacity
Solution Approach 1:
The liquid surface height detection device measures and stores the actual liquid surface height before dispensing begins. This preliminary measurement allows the system to calculate an appropriate threshold voltage based on the actual sample volume, rather than assuming maximum capacity, thereby improving sensing accuracy without significantly complicating the control system.
Solution Approach 2:
The threshold voltage is dynamically adjusted based on the detected liquid surface height. Instead of using a fixed threshold based on maximum capacity assumptions, the system adapts the threshold voltage according to the actual sample volume, enabling accurate liquid surface detection across varying sample quantities.
2Device complexity
If a fixed threshold voltage is used for liquid surface sensing, then the sensing circuit is simplified, but the dispensing accuracy deteriorates when sample volume varies
Solution Approach 1:
The threshold voltage parameter is changed dynamically based on the detected liquid surface height. The system calculates and applies different threshold voltage values corresponding to different sample volumes, ensuring accurate liquid surface sensing and dispensing accuracy across varying sample quantities without requiring a fundamentally more complex sensing circuit.
3Ease of operation
If the liquid surface sensing is based on maximum capacity assumption, then the device operation is simplified, but the dispensing reliability deteriorates when sample amount is less than maximum
Solution Approach 1:
The system performs a preliminary measurement of the actual liquid surface height before dispensing operations. This advance detection ensures that subsequent dispensing operations are based on accurate sample volume information, maintaining reliability even when sample amounts vary from maximum capacity, while keeping the overall operation straightforward.
Solution Approach 2:
The liquid surface height detection device provides feedback about the actual sample volume to the dispensing control system. This feedback mechanism ensures that dispensing operations are adjusted according to the actual sample amount, maintaining high reliability across different sample volumes without complicating the ease of operation.
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
Ensures accurate and stable dispensing regardless of the sample or reagent amount in the container, minimizing errors and enhancing the precision of liquid surface detection.
Implementation Method 1
a liquid surface sensing unit configured to output, based on a change in an electrostatic capacity between the dispensing probe and the sample accommodated in the sample container, a liquid surface sensing signal indicating that the dispensing probe is in contact with the sample
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
To enable accurate and stable dispensing regardless of an amount of a sample accommodated in a sample container at a stage when the sample container is loaded into an automatic analyzer. The automatic analyzer includes a liquid surface height detection device 13 configured to detect a liquid surface height of a sample accommodated in a sample container 11a, a dispensing device 21 configured to dispense the sample by a dispensing probe 42, a liquid surface sensing unit 50 configured to output, based on a change in an electrostatic capacity between the dispensing probe and the sample accommodated in the sample container, a liquid surface sensing signal indicating that the dispensing probe is in contact with the sample, and a dispensing control unit 44 configured to control an operation of the dispensing device. The liquid surface sensing unit includes a liquid surface sensing circuit whose output voltage changes depending on the electrostatic capacity between the dispensing probe and the sample accommodated in the sample container and generates a liquid surface sensing signal for stopping the lowering of the dispensing probe by comparing the output voltage of the liquid surface sensing circuit with a threshold. The threshold is set based on at least the liquid surface height of the sample detected by the liquid surface height detection device.