Abstract: A gravitational compensating system that eliminates gravitational torque of linked robotic arms is provided. A three arm embodiment is disclosed which rotates around a vertical reference axis. The second and third arm rotate around two separate horizontal axes. The gravitational compensating system compensates for the gravitational torque attributed to the second arm as it rotates about its horizontal swing axis and the gravitational torque attributable to the third arm as it rotates about its horizontal swing axis. The combined actuating and compensating systems for the second and third arm are housed in the base structure of the first arm. The compensating system also applies to two arm embodiments.

Abstract: An interferometric device is provided for measurement of the variations in length of a sample under the influence of temperature, the length of the sample being within a plane of reference and a plane of measurement defined by two plane terminal faces of the sample.