Printed strain gauges embedded in organic coatings - analysis of gauge factor and temperature dependence

In this work we present a method for the realization of printed strain gauges on pre-coated sheet steel substrates. The state of the art is to glue strain gauges on foil onto a substrate. This, however, has inherent disadvantages in terms of force coupling between the surface strain on the bent substrate to the glued strain gauge sensors. The fact that the glue and the substrate have in general different moduli of elasticity affects the achievable gauge factor of the final sensor stack. The method presented in this work circumvents these problems completely by avoiding the gluing process altogether and integrating the sensor into a cover layer on the substrate. In the considered case, the substrate is a steel sheet with an organic coating. We integrate the sensor in this coating by printing it on a pre-coated layer. We present comparative measurements of carbon black based sensors, as well as polymeric silver ink based sensors.