Improving the performance of piezoresistive force sensors by modeling sensor capacitance

Piezoresistive force sensors exhibit considerable lower accuracy compared with load cells and force measuring systems based in strain gauges, however a new method for measuring forces using piezoresistive sensors is described in this paper, leading to a considerable increase in the repeatability of force readings. The new method consists of reading sensor´s conductance and capacitance by applying DC and sinusoidal waveforms, thereby allow us to determine a multivariable estimation of force, instead of using the traditional, purely resistive model that has been used up to now. A study of sensor nonlinearities is also described which will allow us to determine the optimal setup to perform capacitance readings under sinusoidal excitation.