Capacitance Detection for Automatic Analyzer Dilution Control
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Solution Overview
Problem
The dilution of samples and reagents in automatic analyzers can exceed acceptable levels due to nozzle cleanliness and system water temperature, and insufficient segmenting air can lead to contamination between samples, affecting analysis accuracy.
Innovation Solution
A capacitance detection mechanism is used to monitor the conductivity and capacitance changes between the nozzle and system water, allowing for real-time detection of sample dilution and contamination, enabling corrective actions such as internal cleaning and re-dispensing to maintain analysis accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high-pressure pump is used for internal cleaning of the nozzle, then cleaning effectiveness is improved, but reliability deteriorates when the pump fails or deteriorates
Solution Approach 1:
The capacitance detection mechanism continuously monitors the electrical capacitance between the nozzle and system water, providing real-time feedback on the degree of sample mixing. When capacitance exceeds a threshold indicating contamination, the system automatically triggers corrective actions such as additional internal cleaning cycles or dispensation interruptions, ensuring reliable operation even when pump performance degrades
Solution Approach 2:
The patent replaces reliance on mechanical pump pressure with an electrical field-based detection system. By measuring capacitance changes caused by ionic contamination in the system water, the system can detect mixing without depending on the mechanical integrity of the high-pressure pump, thus substituting a mechanical reliability concern with an electrical measurement approach
2Manufacturing precision
If dummy suction technique is used to prevent dilution, then sample dilution control is improved, but analysis time increases
Solution Approach 1:
The capacitance detection mechanism provides real-time monitoring during the dispensation process, detecting sample mixing as it occurs. This continuous feedback allows the system to identify actual contamination events rather than assuming all samples require extended dummy suction, enabling selective application of corrective measures only when needed
Solution Approach 2:
Instead of applying excessive dummy suction to all samples uniformly, the system applies cleaning or re-dispensing actions only partially - specifically when capacitance measurements indicate actual contamination. This selective approach maintains precision where needed while minimizing time loss for samples that don't require intervention
3Reliability
If segmenting air is not secured normally, then sample contamination occurs, but detection capability is insufficient without additional sensors
Solution Approach 1:
The patent replaces the need for complex mechanical sensors to detect air segmentation failures with an electrical field-based capacitance measurement system. The system detects the presence of ionic sample material in the system water through changes in electrical capacitance, substituting mechanical detection with an electrical measurement approach that is more sensitive and easier to implement
Solution Approach 2:
The capacitance detection mechanism acts as an intermediary between the physical state of the system water and the control system. By measuring electrical capacitance changes caused by ionic contamination, it translates physical contamination into an electrical signal that can be processed by the control unit, enabling indirect but effective detection of segmentation failures
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 approach effectively restricts the decrease in analysis accuracy caused by dilution and contamination, improving the overall accuracy of sample and reagent dispensation in automatic analyzers.
Implementation Method 1
the area of the system water acting as an electrode is added to the area of an electrode on the nozzle side, and a phenomenon in which the capacitance between the electrode on the nozzle side and a chassis increases is generated
Data Source
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AI summary
Dilution of a sample occurring in a sample dispensing operation is a problem in terms of analysis accuracy. Although the dilution amount is alleviated to some extent by a technique of sucking the sample excessively, the problem may emerge along with a requirement for reducing the sample dispensing amount, an increase of sucking and discharging speed in response to improvement of a processing capability, and an increase of the number of items to be analyzed simultaneously. Provided is an automatic analyzer including a mechanism monitoring conductivity of system water filled in a nozzle and an electro-physical amount such as voltage and capacitance of a probe to enable detection of mixture of the sample and a reagent into the system water and dilution of the sample and the reagent.