Reagent Dispensing Bubble Detection Using a Liquid Surface Sensor
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Solution Overview
Problem
Existing methods for detecting bubbles on liquid surfaces in automatic analysis devices are costly due to the need for additional functions like pressure waveform measurement or image processing, and they struggle to accurately detect strong bubbles that are not broken by the dispensing mechanism.
Innovation Solution
An automatic analysis system with a reagent dispensing mechanism and a liquid surface sensor that performs multiple raising and lowering operations to detect bubbles at different positions, allowing for accurate bubble detection without additional costly mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure waveform measurement or image processing functions are added to detect bubbles, then bubble detection accuracy is improved, but device cost increases
Solution Approach 1:
The liquid surface sensor performs dual functions: detecting the liquid surface position and detecting bubbles. The sensor serves itself by using its existing detection capability to identify bubbles based on unexpected liquid surface position changes, eliminating the need for separate pressure waveform measurement or image processing systems.
Solution Approach 2:
The liquid surface sensor is designed to perform multiple functions: it detects both the liquid surface position during normal operation and identifies bubbles by detecting abnormal position changes. This multi-functionality allows the same component to address both liquid level monitoring and bubble detection without adding extra hardware.
2Measurement precision
If the liquid surface sensor detects the liquid surface during suction operation, then bubble detection capability is improved, but the liquid surface position changes making detection difficult
Solution Approach 1:
The liquid surface position is detected before the suction operation begins. This preliminary detection establishes a reference position that can be compared against subsequent positions during suction, allowing bubble detection based on unexpected deviations from the predicted position change.
Solution Approach 2:
The system compares the actual liquid surface position during suction with the expected position change based on the dispensing amount. When the actual position deviates from the expected position, the system identifies this as a bubble presence, using feedback from the position measurement to detect anomalies.
3Reliability
If strong bubbles are present on the liquid surface, then they are not broken by the dispensing mechanism, but they are erroneously detected as the liquid surface
Solution Approach 1:
The liquid surface position is detected before suction operation to establish a reference point. Strong bubbles that are not broken during suction will cause the detected position to differ from this reference, allowing their identification as false positives rather than actual liquid surface positions.
Solution Approach 2:
The system uses feedback from comparing detected liquid surface positions with expected positions based on dispensing amounts. When strong bubbles cause erroneous detection, the position deviation from expected values provides feedback that identifies these cases as bubble presence rather than actual liquid surface.
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
Accurately detects bubbles of varying strengths without increasing the system's cost, ensuring precise liquid surface detection and preventing errors in dispensing amounts.
Implementation Method 1
a liquid surface is detected based on a fact that static capacitance between the probe and a disk holding a container is different between when a tip end of the probe is in air and when the tip end of the probe is in a liquid
Data Source
Figure 1
Figure 2(a)~2(e)
Figure 3(a)~3(d)
AI summary
According to the present invention, a chemical dispensing mechanism 115 is provided with a liquid surface sensor for detecting the liquid surface of a chemical. A chemical container 122 is mounted on a chemical disk 116. A computer 132 has a calculation control unit comprising a control unit 140 and a calculation unit 141 and generating a control signal for controlling the operation of the chemical dispensing mechanism 115. The calculation control unit performs a first raising operation, in which a chemical stored in the chemical container 122 is suctioned by the chemical dispensing mechanism 115 and the chemical dispensing mechanism is then raised up to a first bubble detection position, determines whether a liquid surface is present by acquiring the detection result of the liquid surface sensor, and outputs an alert indicating the presence of a bubble on the liquid surface when the liquid surface has been determined to be absent. The first bubble detection position is the position at which the tip section of a dispensing nozzle of the chemical dispensing mechanism 115 remains inside the liquid when there are no bubbles present on the liquid surface, and is exposed from the inside of the liquid when there are bubbles present on the liquid surface.