Capacitive Liquid Level Probe Connection for Clinical Analyzers
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Solution Overview
Problem
Clinical analyzers face challenges in determining liquid levels in containers using capacitive liquid level detection circuits due to unreliable connections and interference from external electromagnetic influences, which complicates probe replacement and increases the risk of false positive detection events.
Innovation Solution
A capacitive liquid level detection assembly with a spring-loaded pin connection between the printed circuit assembly and the probe, featuring a primary and secondary tube configuration with electrically isolated surfaces, and a fitting that secures the probe within the transfer arm, allowing for a single, tool-less connection and minimizing external interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a screwed connection or expensive connector is used between the probe and capacitive liquid level detection circuit, then the connection reliability is improved, but the probe replacement difficulty increases and tool requirements are introduced
Solution Approach 1:
The connection system is segmented into modular components: a probe with integrated electrical contacts, a printed circuit assembly with corresponding contacts, and a simple fitting that secures them together. This segmentation allows the probe to be easily replaced by detaching only the fitting, while maintaining reliable electrical connections through the integrated contacts designed for repeated mating and dismating cycles
Solution Approach 2:
The electrical connection and mechanical securing functions are merged into a single integrated contact system. The probe contacts and PCA contacts are designed to mate together while being held by the fitting, combining what were previously separate connection and securing operations into one unified interface that maintains reliability without requiring tools for replacement
2Measurement precision
If multiple wires and connection points are used for capacitive liquid level detection, then the detection accuracy is improved, but the device complexity increases
Solution Approach 1:
The probe serves multiple functions: it acts as both the fluid transfer medium and the capacitive sensor for liquid level detection. The single electrical contact on the probe, when connected to the PCA, provides both mechanical connection and capacitive sensing capability, eliminating the need for separate wires and connection points while maintaining detection accuracy
Solution Approach 2:
The probe itself serves as the capacitive sensor, using its own structure and electrical contact to detect liquid level changes. The probe's capacitance changes naturally when it contacts liquid, and this self-generated signal is read by the PCA, eliminating the need for additional sensing components or complex wiring
3Device complexity
If no grounded shield is used on the probe, then the device complexity is reduced, but false positive detection events increase
Solution Approach 1:
A grounded shield is implemented as a thin conductive layer or coating on the probe surface, rather than a bulky structural component. This thin film provides electromagnetic shielding to prevent false positive detection events from external interference, while adding minimal complexity and maintaining compatibility with the simple connection design
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 solution provides a reliable, accurate, and easily replaceable capacitive liquid level detection system that reduces false positives and simplifies probe replacement, ensuring precise liquid level detection and minimizing carryover and spatter.
Implementation Method 1
a capacitive liquid level detection circuit attached to a probe in a transfer arm... measures the capacitance of the probe many times per second. When the probe touches liquid (or any material with different dielectric or conductive properties), the measured capacitance changes suddenly
Implementation Method 2
When the probe touches liquid (or any material with different dielectric or conductive properties), the measured capacitance changes suddenly
Implementation Method 3
a capacitive liquid level detection printed circuit assembly (PCA) comprising a plurality of spring-loaded pins... a fitting configured to secure the probe within the transfer arm and thereby establish a connection between the capacitive liquid level detection PCA and the probe
Data Source
AI summary
Embodiments are directed to a simple, tool-less, and automated connection between a transfer probe and a capacitive liquid level detection printed circuit assembly (PCA) for use in a clinical analyzer in an in vitro diagnostics (IVD) environment in a hospital or laboratory setting. Advantageously, a single user connection is required: a fitting that is used to attach fluid tubing of the transfer arm to a probe, resulting in a mechanical, fluid, and electrical connection between the probe and the transfer arm. A PCA comprises a plurality of spring-loaded pins and capacitive liquid level detection circuity. A probe comprises a primary tube nested within a secondary tube, wherein the primary tube and the secondary tube comprise respective heads at respective top portions thereof forming a set of electrically isolated surfaces. The fitting secures the probe within a transfer arm and establishes the connection between the PCA and the probe.