Self-Calibrating Polymer Nano Composite Sensing Element
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Solution Overview
Problem
Resistive sensors face challenges in accurately measuring environmental or structural conditions due to influences from contact resistance and background resistance drifts caused by factors like temperature, strain, or aging, which can lead to inaccurate readings.
Innovation Solution
A self-compensating sensor system using a polymer nano composite (PNC) film with multiple electrodes allows for the determination of contact-resistance-independent resistance values by taking multiple two-terminal resistance measurements, enabling the subtraction of background resistance variations and thus providing a calibrated resistance indicative of environmental or structural conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple two-terminal resistance measurements are taken between various pairs of electrodes to determine contact-resistance-independent resistance, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The sensing element is segmented into multiple portions (sensing portion and reference portion) with distinct functions. The sensing portion measures environmental conditions while the reference portion compensates for background drifts. This segmentation allows the system to achieve high measurement precision through differential measurement without requiring complex external calibration equipment.
Solution Approach 2:
The sensor performs self-calibration by using its own reference portion to compensate for background resistance drifts. The measurement circuit automatically calculates compensated resistance values by comparing sensing portion readings with reference portion readings, eliminating the need for external calibration equipment or manual calibration procedures.
2Measurement precision
If a reference portion is added to compensate for background resistance drifts, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The reference portion and sensing portion are merged into a single integrated sensing element on the same substrate. Both portions share the same material properties and manufacturing process, ensuring they experience identical background drifts. This merging allows the reference portion to effectively compensate for drifts in the sensing portion while maintaining a simple, compact device structure.
Solution Approach 2:
Different portions of the sensing element have different local qualities: the sensing portion is designed to be sensitive to environmental conditions (e.g., exposed to corrosion or strain), while the reference portion is designed to be insensitive (shielded or protected). This local differentiation enables precise measurement while keeping the overall device simple.
3Measurement precision
If contact resistance effects are eliminated through multiple measurements, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The measurement circuit automatically performs the complex task of taking multiple resistance measurements and calculating contact-resistance-independent values without user intervention. The system self-calibrates by using the reference portion to eliminate contact resistance effects, maintaining high measurement precision while keeping the operation simple for the user.
Solution Approach 2:
The measurement circuit uses feedback from the reference portion to automatically compensate for contact resistance effects in real-time. By continuously monitoring the reference portion and adjusting measurements accordingly, the system maintains high precision without requiring manual calibration or complex user operations.
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 reduces errors from contact resistance and background drift, enabling more accurate measurements of structural health conditions or environmental changes, such as corrosion or crack lengths, without the need for separate calibration components.
Implementation Method 1
one or more physical characteristics of the target material may change in response to a change in structural health condition of the monitored component
Implementation Method 2
a target material may be subject to corrosion when exposed to certain temperature, mechanical vibration, humidity or moisture conditions over a period of time
Data Source
AI summary
Aspects of the present application allow for measurement of a calibrated resistance for a resistive film in a sensing element, such that effects from contact resistance and background resistance drifts due to factors such as temperature, strain or aging can be reduced or eliminated. In some embodiments, by taking a plurality of two-terminal resistance measurements between various pairs of electrodes on a resistive film, a contact-resistance-independent resistance of a reference portion of the resistive film can be determined. Further, a contact-resistance-independent resistance of a sensing portion of the resistive film can be determined based on a plurality of two-terminal resistance measurements between pairs of electrodes. The resistance of the reference portion can be removed from the measured resistance of the sensing portion, such that variations in the reference portion resistance that are not caused by a sensed environmental condition may be compensated.