A theoretical and experimental investigation of accelerometer design using thick-film technology

Abstract

This thesis describes research undertaken to develop a low-cost accelerometer using thick-film strain gauge transduction elements. A systematic design process was adopted, including a study of substrate materials, evaluation of the fatigue life of the transducer, investigations of the mechanical and thermal properties of thick-film inks, and an assessment of the limits on resolution imposed by the intrinsic noise characteristics of thick-film resistors.The research has shown that fatigue is unlikely to be a problem for thick-film transducers and has led to a new explanation of the nature of thermally-induced resistance changes observed in thick-film resistors. It has also been shown that since the thick-film resistor noise exhibits a 1/f characteristic the resolution of the transducer is frequency dependant.The accelerometer design adopted uses thick-film strain gauges in a novel 'z-axis' configuration, which confers a number of advantages on the design. Firstly, the thick-film transducers are kept in a state of compressive stress, which is varied by the acceleration in a manner which allows the strain gauges to only experience tensile stress. This makes the design very rugged, and allows the use of ceramic substrates. Secondly, the use of the z-axis technique gives a higher gauge factor than all other methods, thus enhancing the sensitivity of the sensor and simplifying the signal conditioning required