Syringe Pump Electrostatic Capacitance Liquid Detection
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Solution Overview
Problem
In water quality analyzers, it is challenging to detect whether a syringe pump has successfully suctioned a liquid, as traditional methods like liquid level sensors are impractical, and abnormal measured values can occur due to suction failures.
Innovation Solution
The method involves detecting changes in electrostatic capacitance between a pair of electrodes attached to the syringe of the syringe pump, with the electrodes configured to differentiate between liquid and air phases, allowing for automatic detection of liquid suction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a liquid level sensor is inserted into the syringe to detect liquid suction, then detection accuracy is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The detection electrodes are integrated directly onto the syringe barrel surface, merging the detection function with the existing syringe structure. This eliminates the need for separate liquid level sensors and reduces overall device complexity while maintaining detection capability
Solution Approach 2:
The patent uses electrostatic capacitance as an intermediary physical quantity to indirectly detect liquid presence. Instead of directly sensing liquid level with a complex sensor, the system measures capacitance changes between electrodes, which vary depending on whether liquid or air is present in the syringe
2Device complexity
If traditional monitoring methods are used to detect syringe pump operation, then device simplicity is maintained, but detection of actual liquid suction failure is impossible
Solution Approach 1:
The system continuously monitors electrostatic capacitance between electrodes during syringe pump operation and provides feedback about liquid suction status. This feedback mechanism enables real-time detection of suction failures without adding complex hardware
3Measurement precision
If electrodes are placed close together on the syringe to improve detection sensitivity, then detection precision is improved, but risk of electrical interference and manufacturing difficulty increase
Solution Approach 1:
The patent applies different electrode configurations to different regions of the syringe barrel. By strategically positioning electrodes at specific locations where capacitance change is most pronounced during liquid suction, the system achieves high detection precision while maintaining simple, manufacturable electrode structures
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 enables reliable and automatic detection of liquid suction by the syringe pump, preventing abnormal measured values and ensuring normal operation of the water quality analyzer.
Implementation Method 1
detecting a change in electrostatic capacitance between a pair of electrodes provided to a syringe
Implementation Method 2
A liquid and air differ from each other in dielectric constant (a dielectric constant of air being about 1/80 of a dielectric constant of water). Accordingly, an amount of electrostatic capacitance in a space in the syringe largely differs between a case where a liquid phase exists in the space and a case where an air phase exists in the space
Data Source
AI summary
Provided is method of detecting presence or absence of a liquid suctioned by a syringe pump. The method includes, in a following order: a step of detecting a change in electrostatic capacitance between a pair of electrodes provided to a syringe, having a tubular shape in which a piston is moved in an axial direction of the syringe, of a syringe pump; and a step of detecting that liquid suction has been performed by the syringe pump based on the change in the electrostatic capacitance.