Probe Unit Shielding for Low Conductivity Measurement
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Solution Overview
Problem
Existing probe units for capacitive and conductive level measurement face challenges in accurately measuring media with low electrical conductivity, such as distilled water, molasses, or oils, due to interference and the need for precise electronics to detect femtofarad capacitances, and lack effective electrical shielding, leading to signal interference issues.
Innovation Solution
A probe unit with a coaxial design featuring a rod-shaped probe electrode, a coaxially surrounding guard electrode, and a contacting module using a flexible printed circuit board with conductive tracks, where the module housing provides electromagnetic shielding and a compact, space-saving design to prevent interference and ensure complete electrical shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the probe unit is designed to be essentially flush with the wall of the container, then the device complexity is reduced and installation is simplified, but the measured capacitance values become extremely small (femtofarad range) requiring extremely high precision electronics
Solution Approach 1:
The patent introduces a contacting module as an intermediary component between the probe electrode and the measurement electronics. This module includes a flexible printed circuit board with contact areas that can be folded to achieve proper electrical contact while maintaining the flush design of the probe unit with the container wall.
Solution Approach 2:
The patent employs a flexible printed circuit board that can be folded in multiple dimensions to achieve the necessary contact geometry. The contact areas on the flexible PCB can be folded relative to each other to establish proper electrical contact with the probe electrode while keeping the overall probe unit flush with the container wall.
2Ease of manufacture
If the probe electrode is not completely surrounded by the additional electrode, then the manufacturing process is simplified, but electromagnetic interference affects the measurement accuracy
Solution Approach 1:
The contacting module with the flexible printed circuit board acts as an intermediary shielding structure. The PCB and its associated components provide electromagnetic shielding for the probe electrode in the area where it is not surrounded by the additional electrode, thereby maintaining measurement reliability while simplifying manufacturing.
Solution Approach 2:
The patent extracts the shielding function from the additional electrode and implements it separately through the contacting module and flexible PCB structure. This allows the probe electrode to be partially exposed for manufacturing simplicity while still providing electromagnetic shielding through the contacting module.
3Stability of the object's composition
If a rigid PCB is used for contacting the electrodes, then the structural stability is improved, but the ability to adapt to different probe geometries and achieve proper contact is reduced
Solution Approach 1:
The patent transitions from a rigid PCB to a flexible printed circuit board that can dynamically adapt its shape. The flexible PCB can be folded and bent to match different probe electrode geometries and achieve proper electrical contact, while still maintaining structural stability through its layered construction and mounting arrangement.
Solution Approach 2:
The patent changes the physical parameter of the PCB from rigid to flexible. This parameter change allows the PCB to conform to different probe geometries and achieve proper contact areas, while the flexible PCB's construction maintains sufficient structural stability for reliable electrical contact.
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 effectively shields the probe electrode from interference, enhancing measurement accuracy and reliability, especially for short probe units flush with the container wall, while being cost-effective and suitable for various media types.
Implementation Method 1
a flexible printed circuit board with at least a first conductor track for electrically contacting the probe electrode and a second conductor track for electrically contacting the guard electrode
Implementation Method 2
The contacting module furthermore comprises a module housing made of an electrically conductive material, in particular metal
Implementation Method 3
the insulating sleeve at least in the area of the support element and the flexible circuit board at least in the area of the two contact areas
Data Source
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AI summary
Probe unit (1) having, at least in sections, a coaxial structure comprising a probe electrode (5), an additional electrode (6) and a contacting module (8) arranged on a section of the probe electrode, which contacting module (8) comprises at least one insulating sleeve (13), a flexible circuit board (16) with at least one first conduction path (17) for the electrical contacting of the probe electrode (5) and a second conduction path (18) for the electrical contacting of the additional electrode (6), and a module housing (20), wherein a first contact plate (19) is provided which electrically contacts the first conduction path (17), and wherein the module housing (20) comprises a second contact plate (24) which electrically contacts the second conduction path (18), wherein the module housing (20) has a pot shaped geometry with a cylindrical wall (25), which wall substantially surrounds, protects and/or electromagnetically shields at least the probe electrode in the region in which the contacting module is arranged, at least a part of the insulating sleeve (13) and at least sections of the flexible circuit board (16).