Framework for a Calibration-Less Operation of Force Sensing Resistors at Different Temperatures

Force sensing resistors (FSRs) typically exhibit noticeably different responses from one device to another, and thus, an individual time-consuming calibration is required for each device. With the aim of speeding-up the development process of applications involving FSRs, a framework for a calibration-less operation of FSRs is presented. The method is based on performing periodic updates on the output voltage at null force and on employing a unique sensitivity value. Dynamic forces were applied at different temperatures to 96 FlexiForce sensors manufactured by Tekscan, Inc. The sensors exhibited rather constant sensitivity values at the temperatures spanning between 24 °C-60 °C. Conversely, the output voltage at null force showed a non-deterministic behavior when the temperature changed. The proposed method showed higher accuracy than the manufacturer method when measuring small forces, whereas the manufacturer method exhibited higher accuracy when working with large forces. Statistical tools were employed to fit the univariate sensitivity data to probability density functions and to assess the relationship between the FSR parameters and temperature. Finally, the effects of temperature changes over sensors' hysteresis are discussed.