Sensor positioning is critical for achieving a measurement accuracy in the picometre range with capacitive displacement sensors. This thesis discusses the contradictory requirements that the sensor alignment application imposes: motion capability combined with extreme displacement stability. In addition, it explores three micrometre scale positioning methods that do not compromise the position stability. All three positioning methods use the properties of friction contacts to achieve the combination of stability and position ability.

An autonomous capacitive sensor system for high accuracy and stability position measurement, such as required in high-precision industrial equipment, is presented. The system incorporates a self-alignment funcion based on a thermal stepping motor and a built-in capacitive reference, to guarantee that the relative position between the sensor electrodes is set to 10 ± 0.1µm. This is needed to achieve the performance specifications with the capacitive readout. In addition, an electronic zoom-in method is used to reach the 10 pm resolution with minimum power dissipation. Finally, periodic self-calibration of the electronic capacitance readout is realized using a very accurate and stable built-in resistive reference. The performance is evaluated experimentally and with simulations. Keywords: Capacitive Sensor System, Position Measurement, Self Alignment, Self Calibration, Thermal Actuator