Abstract: A measurement system has a surface sensing device mounted on an articulating probe head, which in turn is mounted on a coordinate positioning apparatus. The surface sensing device is moved relative to a surface by driving at least one of the coordinate positioning apparatus and probe head in at least one axis to scan the surface. The surface sensing device measures its distance from the surface and the probe head is driven to rotate the surface sensing device about at least one axis in order to control the relative position of the surface sensing device from the surface to within a predetermined range in real time.

Abstract: A method of calibrating an articulating probe head comprising the steps of measuring an artefact of known dimensions with the workpiece sensing probe mounted on the articulating probe head, in which the articulating probe head is unlocked. An error functional map is generated corresponding to the difference between the measured and known dimensions of the artefact. Subsequent workpieces are measured with the articulating probe head unlocked and the corresponding correction applied. The true dimensions of the artefact may be determined by measuring it with a probe mounted on an articulating probe head in which the axes of the articulating probe head are locked. A mechanical lock is provided to lock the axes of the articulating probe head.

Abstract: A rotary drive mechanism is disclosed comprising a housing, a first motor having a first rotor and a first stator connected to the housing and a second motor having a second rotor and a second stator connected to the housing characterised in that the second motor is mechanically independent of the first motor whereby acceleration torques of the first motor are at least partially inertia balanced by the second motor. The balancing may be effected by equal and opposite rotation of the second motor. Control means may be provided to provide the second motor with a current which is proportional to that supplied to the first motor. Also disclosed is a positioning device and a probe having the rotary drive mechanism.