Very high strain sensitivity in thick-film resistors: real and false super gauge factors.

An investigation was carried out on the correlations between composition/morphology of RuO2-based thick-film resistors and their strain sensitivity. Very high gauge factors (GFs), as well as satisfactory performance in terms of TCR (temperature coefficient of resistance), excess noise and reliability, are obtained with an appropriate choice of glassy matrix, RuO2 grain size and concentrations. Resistive systems modified with metal and metal oxide additions were analyzed. In some cases, notable changes of electrical properties are observed , related to defective structures. Methods for a simple and accurate diagnosis of reliable or fictitious performance of thick-film strain gauges are identified