Performances and potentialities of a very simple self-compensated pressure sensor demonstrator

A pressure sensor demonstrator has been designed and mounted using a simple analog-digital BiCMOS converter and a capacitive silicon-Pyrex sensing cell. The measurements as a function of pressure and temperature have enabled the authors to evaluate the efficiency of a ratiometric scheme to self-compensate thermal drifts and nonlinearities. The best demonstrator is characterized by a thermal coefficient of offset smaller than 20 ppm/K and a nonlinearity lower than or equal to ±1.2% FS. The essential features of the sensor have been modeled by a simple analytical expression. The model specifies the potential gains in pressure sensitivity and nonlinearity. The best design is based on a quasisymmetrical architecture in which stray capacitors are minimized. This study demonstrates the feasibility of self-compensated capacitive sensors characterized by an overall accuracy of the order of a few percent of the measurement scale over a temperature range of 100 K at very low cost