Object of this paper is the performance analysis of a six degrees of freedom measuring device based on a modified Stewart platform structure. Because of the device studied in this work represents a novel application of a Stewart like platform, an investigation about its performance has been done, in order to evaluate both behaviour and characteristics of this device in different geometrical configurations. In particular, sensitivity analysis has been carried on about geometrical characteristics and displacements amplitude. To calculate the sensitivity, the inverse kinematic equations of the device have been obtained.