Fluidic-coupled high-resolution displacement sensor for low-power wireless applications

This paper presents an innovative high-resolution displacement sensor for low-power-applications, such as wireless systems. The sensor uses the principle of fluidic coupled displacement pressure conversion. The sensor core is based on a piezo-resistive silicon pressure sensor element. A membrane detects the displacement to be measured and changes the pressure of a partly compressible fluid. The change in pressure is then determined by measuring the sensor resistance. In addition, the on-chip temperature is measured and used to increase the sensor accuracy. The measurement range depends on the fluid compressibility and has a typical value of 50 - 100 mum with a resolution of 1 mum. A functional model has been realized and tested in respect to resolution and reliability. Using multiple smart-system integration, a sensor size of 6 mm in diameter and 25 mm in length could be realized.