In collaboration with the company, A. Raymond, we have developed a capacitive low-cost sensor with which the installation status of fluidic quick-release couplings in pre-assembled fuel tanks of motor vehicles can be read-out wirelessly. For this the sensor is formed as a resonant oscillating circuit with variable capacity that can be used to detect whether the coupling is opened or closed. For the first time, manufacturers are enabled to deliver tested fuel tanks that are documented online during the assembly process.
Our sensor demonstrator has the potential of manufacturing high-quality LC oscillating circuits, and thus installation sensors with a one-time function at low cost in small or large quantities, with concurrent high reproducibility of the resonant frequency. However, use of the installation sensor is not limited to fluidic quick-release couplings: Such a sensor can be used for quality monitoring on virtually any connection point, such as electrical, electrical-fluidic or mechanical connections. Because it does not require additional active or passive components, or its own energy supply, it is particularly well-suited for moving or rotating parts. We developed the performance verification in MID technology, and later mapped it in PCB technology. We further developed the sensor for a foil-based structure. In the initial preliminary investigations, double-sided, hot-embossed copper foil structures were applied on a plastic foil substrate. Via resistance welding a through-contacting of both layout sides was implemented. For the one-time function a defined area of the capacitor is irreversibly separated and thus the resonant frequency of the oscillating circuit is permanently changed.
To further reduce the costs for such a sensor, we have investigated and successfully tested aluminum foils from the food packaging industry, as they are used for yogurt lids: Our sensors are fully functional, even after injecting a quick-release coupling in the injection molding.