New digital readout electronics for capacitive sensors by the example of micro-machined gyroscopes

This paper reports a new digital readout electronics for capacitive sensors like accelerometer, gyroscopes or inclinometers. The functional principle of the readout electronics is shown by the example of the micro-machined gyroscope decoupled angular velocity detector (DAVED) developed at HSG-IMIT [Sens. Actuators A 84 (2000) 280]. The goal of this digital concept is to minimize noise and temperature drifts caused by the analog components of the readout electronics. This is feasible, because the main part is done digitally inside a digital signal processor (DSP). Further, this new digital concept is not only used for temperature compensation or force-to-rebalance loops [Algorithm and low power digital implementaion for MEMS inertial sensors, Final report 1999-2000 for MICRO Project 99-083] it is also used to readout the small capacitive changes of the sensor output. First measurement results of the novel digital prototype show a rms noise of 0.21°/s and a nonlinearity of 0.39% (end-point-straight-line) in a measurement range of ±200°/s.