Capacitive Level Sensor With Restricted Substrate
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Solution Overview
Problem
Existing level sensors lack precision and sensitivity in measuring liquid levels, particularly in applications where minimal levels need to be detected accurately.
Innovation Solution
A capacitive level sensor device with enhanced precision and sensitivity is developed, featuring a circuit substrate with strategically positioned electrodes and a overmoulded casing that allows for improved capacitance measurement, incorporating a restricted substrate portion for increased electrode width and sensitivity, and a protective coating to safeguard electronic components during the overmoulding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard circuit substrate is used with uniform width throughout, then the substrate provides adequate structural support and electrical connection, but the electrode width is limited and measurement precision is insufficient
Solution Approach 1:
The circuit substrate features a restricted portion with reduced width specifically at the sensor element location, while other portions maintain standard width. This local modification allows the sensor electrodes to extend closer to the casing opening, increasing their effective width and capacitance for improved level measurement precision, without compromising the overall structural integrity of the substrate
2Measurement precision
If the substrate width is increased throughout to improve electrode width and sensitivity, then measurement sensitivity improves, but the device dimensions increase and it no longer fits standard mounting openings
Solution Approach 1:
Instead of uniformly increasing substrate width, the invention locally modifies the substrate geometry at the sensor portion only. The restricted portion allows electrode extension for improved sensitivity, while the overall substrate dimensions remain compatible with standard mounting openings. This localized approach achieves enhanced measurement capability without increasing overall device footprint
3Manufacturing precision
If electronic components are exposed during overmoulding to allow precise positioning, then component placement accuracy improves, but the components are vulnerable to damage from molten material
Solution Approach 1:
Electronic components are positioned on the substrate before the overmoulding process begins. The substrate's restricted portion is designed to accommodate these components in their final positions. The overmoulding material is then applied, automatically encapsulating and protecting the pre-positioned components without requiring subsequent handling or exposure, thus preventing damage while maintaining positioning accuracy
4Measurement precision
If the sensor element extends further into the container to improve minimal level detection, then detection capability improves, but the risk of damage from molten overmoulding material increases
Solution Approach 1:
The sensor element is positioned in its final extended position before the overmoulding process. The substrate structure, particularly the restricted portion, is designed to support the sensor element at this extended position. During overmoulding, the molten material is contained and directed away from the sensor element, allowing the element to extend sufficiently for improved minimal level detection while being protected from damage by the manufacturing process
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 sensor device achieves enhanced precision and sensitivity in detecting minimal liquid levels, ensuring accurate measurements while maintaining cost-effectiveness and reliability.
Implementation Method 1
A level sensor of the type referred to above is known, for example, from WO 2015/181770 A... The sensor device (10) comprises a capacitive sensor element (23)
Data Source
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Figure 5~6
AI summary
A capacitive level- sensor device comprises: - a circuit substrate made of electrically insulating material (20) that extends longitudinally according to a level-sensing axis; - a first array of electrodes or capacitive elements on a sensing region (23) of the circuit substrate (20), which comprises at least one first series of first electrodes (J1-Jn) coplanar to one another at a major face of the circuit substrate (20); - a circuit, which comprises circuit components associated to a second region (24) of the circuit substrate (20); and - a casing body (14-16), which comprises at least: a sensing portion (15), which is electrically insulating and fluid- tight and coats at least the sensing region (23) of the circuit substrate (20); and a mounting portion (14, 16), which coats at least partially the second region (24) of the circuit substrate (20) and is configured for fluid- tight fixing at an opening (6) of a container (1). The sensing portion (15) and at least part of the mounting portion (14, 16) comprise at least one material (M) overmoulded on at least part of the circuit substrate (20). The second region (24) of the circuit substrate (20) includes at least one restricted substrate portion (30), having a substrate width (Wr) smaller than the substrate width (W) of the sensing region (23). At least part of the at least one restricted substrate portion (30) extends axially in the mounting portion (16).