Capacitance Liquid Level Sensor with Segmented Platform
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Solution Overview
Problem
Existing liquid level sensors in automated analytical instruments face inaccuracies and noise in capacitance measurements due to poorly defined capacitor configurations and interference from large surface areas, leading to erroneous liquid level determinations.
Innovation Solution
The solution involves an electrically conductive support with a raised platform of smaller area than the support, focusing the electric field onto the platform where the liquid container is placed, and using a capacitance sensor to measure the capacitance between the conductive tip and the platform, allowing for precise liquid level determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large surface area support is used for the capacitance sensor, then the sensor can detect liquid levels across a wider area, but the measurement precision deteriorates due to interference and poorly defined capacitor configurations
Solution Approach 1:
The support surface is segmented into a large base support structure and a smaller, elevated platform region. This segmentation allows the large support area to provide structural stability while the smaller platform region defines the precise capacitor measurement zone, reducing interference and improving measurement precision.
Solution Approach 2:
Different regions of the support structure are assigned different functional qualities: the large base support provides mechanical stability and grounding, while the smaller elevated platform provides a focused, well-defined capacitor measurement area with reduced interference. This local differentiation resolves the contradiction between large area coverage and precise measurement.
2Area of stationary object
If the electrically conductive platform has a large area, then it can support larger containers, but the capacitance measurement becomes noisy and less reliable
Solution Approach 1:
The platform is segmented as a distinct elevated structure separate from the large support base. This segmentation allows the platform to be optimized for precise capacitance measurements with a controlled, smaller area, while the larger support base provides structural support and grounding without contributing to measurement noise.
Solution Approach 2:
The elevated platform acts as an intermediary between the large support structure and the capacitance sensing elements. It provides a focused measurement zone that is electrically isolated from the large support base, thereby mediating between the need for structural support and the need for clean, noise-free capacitance measurements.
3Device complexity
If the capacitor configuration uses the instrument deck as one plate, then the device complexity is reduced, but the measurement precision deteriorates due to interference from the large surface area
Solution Approach 1:
The capacitor configuration is segmented into two distinct plates: the elevated conductive platform and the conductive tip. This segmentation creates a well-defined, localized capacitor field that eliminates interference from the large instrument deck surface, improving measurement precision while maintaining relatively simple device complexity.
Solution Approach 2:
The measurement function is extracted from the large instrument deck and concentrated into the smaller elevated platform. This extraction removes the source of interference (the large deck surface) from the measurement process, allowing for precise capacitance measurements without requiring complex shielding or interference cancellation circuitry.
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 enhances the accuracy and reliability of liquid level sensing, reducing noise and improving the robustness of measurements, enabling accurate pipetting and dispensing of liquids while simplifying the fabrication of tailored platforms for liquid level sensing.
Implementation Method 1
a capacitance sensor coupled to the electrically conductive element (c) and arranged to provide an electrical signal representing the capacitance
Implementation Method 2
focusing the electric field onto the platform where the liquid container is placed
Data Source
AI summary
An apparatus and method for determining the level of liquid in a container in an analytical instrument, typically an automated analytical instrument in a laboratory. The apparatus comprises:(a) an electrically conductive support;(b) an electrically conductive platform rising up from said electrically conductive support, said platform capable of supporting at least one container that is capable of containing a liquid, said platform having an area less than that of the electrically conductive support;(c) an electrically conductive element, such as, for example, the electrically conductive tip of a probe, the distance between the electrically conductive platform and the electrically conductive element capable of being reduced or increased by relative movement between the electrically conductive element and the electrically conductive platform; and(d) a capacitance sensor coupled to the electrically conductive element (c) and arranged to provide an electrical signal representing the capacitance.