A Geometric Design Study of High-Temperature Position Sensors

Abstract

In this paper, we propose the position sensor designs for high-temperature applications. Oxidation and the chemical reaction of resistive elements, together with the mechanical degradation of component materials at high temperatures, limit the high-temperature applications of conventional position sensors. In order to overcome these drawbacks of conventional position sensors, we designed position sensors consisting of a resistive element, a passivation layer, contact pads, and a conductive brush. The oxidation and chemical reactions of the resistive elements at high temperatures can be prevented by using a passivation layer that has excellent chemical resistance and hardness. Inorganic materials and noble metals that can withstand high temperatures have been used for the resistive elements, the substrate, the electrodes, and the brush. The output signal characteristics of the proposed position sensors are determined mainly by the geometries of the contact pads and the brush. To investigate these geometric effects, three types of position sensors having individual shape of contact pads were fabricated with MEMS technologies and a preliminary performance evaluation at room temperature was carried out. From the preliminary test results, we concluded that S-types were appropriate for high-temperature applications and carried out the performance tests at high temperatures with the S-type position sensor.