Capacitive Fluid Level Sensing for Surgical Cassette Reservoirs
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Solution Overview
Problem
Current fluid level sensing methods in ocular surgery, such as float mechanisms, optical, and sound emitter-sensor systems, are unreliable and costly, particularly in environments with condensation, debris, or foam, leading to imperfect air-to-fluid ratio balancing in surgical cassette reservoirs during phacoemulsification procedures.
Innovation Solution
A capacitive fluid level sensing system using a capacitive sensing device with conductive plates forming a capacitor, connected to an electric circuit that measures capacitance changes to control fluid levels in the reservoir, allowing for precise adjustment of the air-to-fluid ratio by operating pumps and valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If float mechanisms or optical/sound emitter-sensor systems are used for fluid level sensing, then fluid level detection can be achieved, but reliability deteriorates in environments with condensation, debris, or foam
Solution Approach 1:
The patent replaces mechanical float mechanisms with a capacitive sensing system that uses electrical fields rather than mechanical components. The capacitive sensor detects fluid level changes through capacitance variations caused by the dielectric properties of the fluid, eliminating mechanical parts that can be affected by condensation, debris, or foam.
Solution Approach 2:
The patent replaces optical or sound emitter-sensor systems with capacitive sensing that uses electrical field interactions. The capacitive sensor measures fluid level through changes in capacitance without requiring optical paths or acoustic waves, making it immune to interference from condensation, debris, or foam that plague optical and acoustic systems.
2Reliability
If float mechanisms or optical/sound emitter-sensor systems are used for fluid level sensing, then fluid level detection can be achieved, but cost increases
Solution Approach 1:
The capacitive sensing system uses simple conductive elements and basic electronic circuitry that are significantly cheaper than optical emitters, sensors, or mechanical float mechanisms. The capacitive sensor can be implemented with inexpensive conductive materials and standard electronic components, reducing manufacturing costs while improving reliability.
3Ease of operation
If manual adjustments are made for fluid level control, then flexibility can be achieved, but productivity decreases due to time consumption
Solution Approach 1:
The capacitive sensing system enables automatic fluid level monitoring and control. The system self-regulates by continuously measuring capacitance changes and triggering pump operations or valve adjustments without requiring manual intervention, thereby maintaining operational flexibility while significantly improving productivity by eliminating time-consuming manual checks and adjustments.
Solution Approach 2:
The capacitive sensor provides continuous real-time feedback on fluid level conditions to the control system. This feedback loop enables automatic control of pumps and valves to maintain optimal fluid levels, eliminating the need for manual adjustments while ensuring the system responds dynamically to changing conditions during surgical procedures.
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
The capacitive system provides reliable, non-invasive, and efficient fluid level sensing, reducing the need for manual adjustments and minimizing errors, ensuring consistent performance during ocular procedures by accurately controlling fluid levels within the surgical cassette reservoir.
Implementation Method 1
a capacitive sensing device with conductive plates forming a capacitor, connected to an electric circuit that measures capacitance changes
Data Source
AI summary
A capacitive fluid level sensing arrangement for use in a medical device is provided. The arrangement includes at least one pair of conductive plates configured to increase and decrease the amount of electric charge stored in relation to the level of fluid within a fluid maintaining device, such as a reservoir. The conductive plates are electrically connected to a medical device and are configured to measure the charge stored between the plates and thus sense the fluid level. The electric circuit may communicate the measurement to an instrument host arrangement for operating a pump configured to remove fluid from the reservoir and move the fluid to a collector when the level exceeds a preset upper level amount. The instrument host arrangement may stop operating the pump when the fluid level is reduced to a preset lower level amount.