A thick-film capacitive pressure sensor with improved linearity due to electrode-shaping and frequency conversion

Various methodologies are applied to the measurement of pressure. Among them, the capacitive pressure sensor is one of the most useful devices due to its high performance-to-price ratio, reliability and low power consumption. However, the early versions of capacitive pressure transducers had a general reputation of being highly nonlinear. This paper discusses a design approach to overcome this problem by choosing a new electrode shaping and coupling the sensor with an electronic circuit based on a relaxation oscillator. Moreover, the output signal in the form of a frequency makes the distance transmission and the interfacing with digital systems easier. The theory of operation is presented with a description of the sensor's implementation in thick-film technology on ceramic substrates and with experimental results on its characterization.