Automatic Analyzer Liquid Level Detection Oscillator Interference
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Solution Overview
Problem
Automatic analyzers using capacitance detection for liquid level measurement face interference due to frequency differences between oscillator signals, leading to erroneous liquid level detection and reduced dispensing accuracy when multiple probes operate simultaneously.
Innovation Solution
The implementation of a high-frequency attenuator that reduces noise by setting the frequency difference between detector oscillators to several kHz, allowing for accurate liquid level detection and improved dispensing reliability, even when multiple probes are used simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple probes simultaneously detect liquid levels using capacitance detection with oscillators, then dispensing speed and productivity are improved, but frequency interference between oscillators causes erroneous liquid level detection
Solution Approach 1:
The patent applies periodic action by sequentially activating oscillators in different probes at different time intervals rather than simultaneously. The controller activates oscillators in a time-division manner, ensuring that only one oscillator is active at any given moment. This periodic activation eliminates frequency interference between multiple probes while maintaining high dispensing speed through rapid sequential operation.
2Productivity
If multiple probes operate simultaneously for high-speed dispensing, then processing efficiency is improved, but frequency signal interference causes detection errors
Solution Approach 1:
The system implements periodic action through time-division multiplexing of oscillator activation. Each probe's oscillator is activated in a sequential, periodic manner controlled by a controller, ensuring that oscillators do not operate simultaneously. This approach maintains high processing efficiency through rapid cycling while ensuring detection reliability by eliminating frequency interference between probes.
3Measurement precision
If liquid level detection is performed using capacitance change method, then measurement capability is improved, but frequency differences between oscillators create interference signals
Solution Approach 1:
The patent applies the taking out principle by extracting the oscillator activation process from simultaneous operation and separating it into sequential, independent activation events. The controller extracts the harmful frequency interference by ensuring that oscillators are activated one at a time rather than simultaneously, thereby eliminating the interference while preserving the capacitance detection capability for accurate liquid level measurement.
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 configuration minimizes erroneous liquid level detection and enhances dispensing accuracy, ensuring precise liquid handling and reducing contamination and wastage, while maintaining a simple system configuration.
Implementation Method 1
a liquid level detector that detects a liquid level in a reagent bottle by a capacitance change when a top end of a reagent probe contacts a liquid surface of a reagent in the reagent bottle
Data Source
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AI summary
In an automatic analyzer using a plurality of probes detecting liquid levels based on a capacitance detection method, erroneous detection of liquid levels due to interference caused by the frequency difference of oscillators are reduced, so that an automatic analyzer with high accuracy at a high speed can be realized. Although frequencies f1 and f2 of detector oscillators 307 and 201 are originally equal to each other, if they are different by approximately several Hz from each other due to a manufacturing variation, oscillation waveforms are added to liquid level detection voltages, and it may be determined that the probes have contacted the liquid surfaces at inappropriate times before appropriate times when the probes have contacted the liquid surfaces. The present invention intentionally makes the difference between the frequencies f1 and f2 of the detector oscillators 307 and 201 be several kHz. In this case, as well as an actual change in capacitance due to the contact with the liquid surfaces, an oscillation waveform corresponding to the difference between the frequencies f1 and f2 is added to detection voltages, but amplitude values of high-frequency components can be attenuated by high-frequency attenuators 208, thereby suppressing a reduction in the liquid level detection accuracy due to simultaneous use of the plurality of probes.