A PLANAR THICK-FILM LOAD CELL

One of the more serious compensation problems for load-cell manufacturers is sensitivity to load eccentricity. The structural and tailored compensation techniques used to overcome this problem tend to make load cells relatively expensive devices. Thick-film technology offers great benefits of robustness and cheapness, but is not very amenable to non-planar structures. In a recent research programme the authors have devoted considerable effort to the study of thick-film gauges printed on stainless steel, and have assembled data characterizing their behaviour and performance. In this paper we describe a novel form of load cell based on a planar tri-beam configuration in stainless steel with an arrangement of printed gauges on each side. Mathematical modelling of the structure suggests that the arrangement yields a low sensitivity to load eccentricity, and this is confirmed by direct measurements on a small-scale physical model. A mathematical analysis has also been made of the effect of gauge resistance errors, and this shows that it is somewhat mitigated by the form of interconnection used. The result of these studies is the design of a load cell suitable for applications of moderate precision (such as the domestic market), which could be extremely cheap to manufacture and robust in application.