Evaluation of microelectromechanical devices for DC and RF voltage measurements

Novel sensors for electrical DC and RF voltage measurements employing the principle of electrostatic force are presented. Microelectromechanical devices have been developed, fabricated and optimized, which are based on multiple capacitances with a common movable electrode. By applying a voltage to one capacitance, a force is generated which is translated into mechanical motion, eventually balanced by the mechanical spring counterforce of the suspension. Operating the device at frequencies above mechanical resonance allows the RMS value of the signal to be measured, supplementing conventional methods. For DC and RF voltage excitation, the resolution has been enhanced to be better than 0.1%. The usable frequency range has been extended beyond 10 Megahertz at RMS voltage levels of less than six volts. Furthermore, a model applied for dimensioning the sensors is presented focusing on high-frequency metrology aspects. By evaluating the frequency dependence of the design parameters, predictions of the measurement range and resolution of the final structures can be made.