Patent ID: 6810597
Filing Date: 2004-11-02
Classification: B82Y,G01B

Abstract:
A method of measuring an artefact using a machine on which a measuring probe is mounted for relative movement with respect to the artefact, said machine having at least one measuring device for providing an output indicative of the relative position of the probe, the probe having a deflectable stylus, and at least one measuring device for measuring deflections of the stylus to provide one or more probe outputs which are indicative of the amount of deflection of the stylus from a rest position, the method being characterised by the steps of:causing relative movement between the probe and artefact to bring the stylus into contact with the surface of an artefact and continuing said movement for a limited distance after initial contact has been made between the stylus and the artefact; recording the outputs of the machine and of the probe at a plurality of instants, during both the periods of contact and non contact between the stylus and the artefact; providing a model of the probe and CMM outputs which models the outputs both during contact and non contact between the stylus and the artefact; fitting the model to the data and thereby determining the values of the outputs of the measuring device or devices of the machine relating to the contact position at which the stylus contacts the artefact with zero contact force; and combining said outputs of the measuring device or devices of the machine at said contact position with the probe deflection at the contact instant to establish the contact position at zero force.