Thick-film Load-sensing bridges – Effect of Temperature and Mechanical Boundary Conditions

Abstract

Although inorganic thick-film materials are usually very stable, load sensors (i.e. force, torque and pressure) based on the piezoresistive effect of thick-film resistors often exhibit some drift, with major contributions stemming from a) temperature changes or gradients, coupled with the temperature coefficient of resistance (TCR) of the sensing bridge resistors, and b) ill- defined mechanical boundary conditions, due to insufficient decoupling, plastic deformation used materials, friction or loading errors. These problems also potentially affect test samples for measuring piezoresistive response, a.k.a. the gauge factors. Here, we examine and discuss effects on the output signal of simple cantilever force sensors of two disturbances: parasitic loads and temperature gradients, and discuss / demonstrate mitigation options, and a system to reliably measure gauge factor.