Design and Implementation of a Capacitive Measurement Circuit with Application to Integrated Micromotor Position Sensing

This thesis presents the design, analysis, and experimental results of a circuit to be used as a position sensor for microfabricated electric motors. The circuit is designed to measure the capacitance between the rotor blades and sensor electrodes implanted into the substrate beneath the rotor. This capacitance typically varies between five and fifteen femtofarads as the rotor turns. Analytic and experimental results show that the circuit is capable of measuring the required changes in capacitance in the presence of picofarad parasitic capacitances with a dynamic response approaching 1 MHz. However, successful implementation of the circuit as a position sensor for real micromotors requires the fabrication of buffer amplifiers in the micromotor substrate between the sensor electrodes and bonding pads.