Development of a new piezoelectric sensor to measure loads

The aim of the project, which includes the development of a new sensor, is to create a completely encapsulated sensor system, which measures the load on a patient´s legs and feet and transfers the data wirelessly to a watch. Therefore it was necessary to develop and test a novel type of sensor. The focus here was on reliability - it will be used on a medical device-and minimal energy consumption. Together with our project partners we decided to use a piezoelectric sensor. The analysis measures the change of capacity caused by the applied load. By gradually changing the parameters thickness, diameter, material and polarization, the sensor was optimized. In addition the hysteresis behavior and temperature dependence was examined. The interdependence between time, heavy loads and capacity was found and had to be compensated. Therefore different ideas for compensating hardware and software were developed, tested and analyzed. Furthermore a suitable case had to be developed and studied, which could prestress the sensor without taking away too much of the load applied to the sensor.