Investigation of the sensitivity of a strain gauge force sensor to bending moment

Abstract

This paper deals with the problem of the sensitivity of strain gauge force sensors to bending moment which badly affects the measurement accuracy. The bending moment sensitivity can be caused by incorrect force sensor geometry, suboptimal arrangement of strain gauges, imprecise positioning of strain gauges during installation, variation of the strain gauges’ properties. In this study we investigate the effects of the strain gauges’ positioning errors and variation of their properties on the bending moment sensitivity for the case of a compression membrane force sensor having axis-symmetrical geometry. Firstly, we obtain the information about the sensor’s stress-strain state when it is loaded with compressive force and bending moment using Finite Element Analysis. The Finite Element Analysis results are used in conjunction with probabilistic modelling techniques for evaluation of the distribution of the bending moment sensitivity. The modelling results have shown that the distribution’s mean value is approximately zero due to the axis-symmetrical geometry of the force sensor. The standard deviation of the bending moment sensitivity depends on the number of strain gauges in the Wheatstone bridge and the gradient of the strain caused by bending moment in the areas where the strain gauges are installed. The proposed method of evaluating bending moment sensitivity can be applied to other kinds of parasitic loads and other types of strain gauge force sensors for minimizing the sensitivity to parasitic loads in single- and multi-axis strain gauge force sensors.