Flexible Capacitive Humidity Sensor for Tire Pressure Monitoring
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Solution Overview
Problem
Current pressure and humidity measurement systems lack efficient and accurate methods for simultaneous measurement and data processing, especially in flexible and dynamic environments like tires, where internal pressure and humidity changes need to be monitored accurately.
Innovation Solution
A capacitive moisture sensor system using a flexible support material with electrodes and a dielectric layer, integrated with a processing unit that measures capacitance changes due to humidity and pressure, transmitting data to a central CPU for processing, and utilizing energy harvesting techniques for power supply, with optional integration into tire materials for internal monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive sensor with dielectric layer is used for humidity measurement, then measurement precision is improved, but the sensor becomes sensitive to liquid contamination which affects reliability
Solution Approach 1:
A liquid-repelling layer is introduced as an intermediary between the dielectric layer and the external environment. This layer has liquid-repelling properties that prevent liquid contamination from reaching the dielectric layer, while still allowing the sensor to detect humidity changes through the repelling layer. The intermediary layer thus protects the sensitive dielectric layer from harmful liquid contact while maintaining measurement functionality.
2Device complexity
If processing unit and CPU are integrated on shared support material, then device complexity is reduced, but measurement accuracy may be compromised due to interference
Solution Approach 1:
The system is segmented into two separate functional units: a processing unit for signal conditioning and a separate CPU for data processing. These units are physically separated and not arranged on the same support material, preventing electrical interference between the high-precision capacitance measurements and the digital processing operations. The segmentation ensures measurement accuracy while maintaining system functionality through distributed architecture.
3Duration of action of moving object
If traditional battery power supply is used, then continuous operation is ensured, but weight and environmental impact increase
Solution Approach 1:
The sensor system is equipped with an energy harvesting device that automatically generates electrical energy from ambient sources (such as mechanical deformation, temperature differences, or vibration) to power the sensor and processing units. This self-service approach eliminates the need for external battery replacement or recharging, providing continuous operation without adding battery weight or environmental waste. The energy harvesting device sustains the system autonomously by converting environmental energy into electrical power.
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
Enables accurate and simultaneous measurement of pressure and humidity, with energy harvesting ensuring continuous operation without batteries, and wireless data transmission for real-time monitoring and control, enhancing tire condition assessment and safety features.
Implementation Method 1
The dielectric constant of the polymer material then changes as a function of moisture content
Implementation Method 2
takes in (absorbs) or releases (desorbs) moisture until an equilibrium state is reached
Implementation Method 3
a capacitance is at least partially changed by the liquid at least partially hitting the dielectric layer
Data Source
AI summary
The invention relates to a measuring system for measuring pressure and/or humidity, comprising at least one apparatus for measuring pressure and/or humidity, comprising at least one sensor for measuring pressure and/or humidity, wherein the sensor comprises at least one capacitor comprising at least two electrodes that are arranged, in particular, in a horizontal direction along and on an, in particular, flexible support material relative to one another. At least one dielectric layer is arranged between the electrodes. The invention is characterised in that at least one at least partially liquid-permeable and/or liquid-absorbing moisture layer is arranged at least in some places on a side, facing away from a support material, of at least one electrode and/or of the dielectric layer. The at least one electrode and/or the dielectric layer are thus then arranged between the support material and the moisture layer in a transverse direction. In this way, a capacitance is at least partially changed by the liquid at least partially hitting the dielectric layer, wherein a processing unit is designed and provided to measure and/or store measurement values of the sensor. This creates a capacitive moisture sensor. The invention is characterised in that the data measured by the sensor is transmitted by the processing unit to a central CPU, wherein this data is processed by the processing unit.