Evaluating and Modeling Force Sensing Resistors for Low Force Applications

There has been an increasing demand for force measurement in applications that are portable, wearable, have limited space, low power, or low cost requirements. Such applications cannot support the power and computing requirements of the load cells. Force sensing resistor (FSR) is a passive component that is composed of polymer thick films that change resistance between its terminals due to force applied at its surface. An FSR can provide a suitable alternative to the bulky load cell. However, it inherently exhibits many nonlinear behaviors. This paper evaluates five different FSR sensors (IEE FSR 151 NS, Interlink FSR 402, Sensitronics ShuntMode FSR. FlexiForce A201 FSR, and Sensitorincs ThruMode FSR). The FSRs were evaluated for sensitivity, minimum measurable force, repeatability, creep, and hysteresis. In addition, system identification techniques were used to model each FSR behavior so they can be used as calibrated standalone force sensors. Results show that the Sensitronics ThruMode FSR had the best repeatability and the least hysteresis, while the FlexiForce A201 had the lowest creep, and the Interlinks 402 FSR had the lowest threshold force.