A system has been developed for investigating the piezoresistive effect in semiconducting solids and conductive polymers under different elastic and thermal boundary conditions. The system provides the necessary information needed for sensor design such as nonlinearity, hysteresis, and temperature dependence of the piezoresistance coefficient. The system operates under full computer control for both data acquisition and data reduction cycles. The temperature dependence of the hydrostatic piezoresistance coefficient of a donor‐doped polycrystalline semiconducting barium titanate below and above its ferroelectric–paraelectric Curie point will be presented for the first time. The nonlinear and hysteretic behavior of an electrically conductive polymer over the pressure range of 0–30 MPa will also be demonstrated.