Thin film sensors for measuring small forces

Abstract

Especially in the case of measuring small forces, the use of conventional foil strain gauges is limited. The measurement uncertainty rises by force shunts and is due to the polymer foils used, as they are susceptible to moisture. Strain gauges in thin film technology present a potential solution to overcome these effects because of their direct and atomic contact with the measuring body, omitting an adhesive layer and the polymer foil. For force measurements up to 1 N, a suitable deformation element was developed by finite element (FE) analysis. This element is designed for an approximate strain of 1000 μm m−1 at the designated nominal load. The thin film system was applied by magnetron sputtering. The strain gauge structure is fabricated by distinct photolithographic steps. The developed sensors were tested with different load increments. The functional capability of the single resistance strain gauges could be proven. Moreover, a developed sensor in a full bridge circuit showed a linear characteristic with low deviation and good stability.