Wireless sensor system for measuring adhesive temperatures
In industry more and more product components are assembled by adhesives. At room temperature adhesives usually need several hours or days to cure. By heating up the adhesive this time can be significantly shortened to some seconds or minutes. The material dependent ideal temperature variation for curing must not exceed an interval of ± 10 °C, otherwise the quality of the junction decreases dramatically. Therefore, the knowledge of the temperature of the adhesive is essential for the control system to obtain an optimal curing process. To measure wirelessly the adhesive’s temperature, an inductive measurement technique has been developed and tested. By using magnetic sensitive particles as filling material for the adhesive and the corresponding Curie effect, the temperature dependent permeability of these sensor particles can be measured, giving direct information about their temperature. With an appropriate mixture of ferrites a temperature span from 135 to 170 °C can be monitored. Within this span the inductance of a suitable coil sensitively changes and gives reliable information about the curing temperature.