The following recognized principles have been used in the development of this design. The length of the metrology loop (that is, the mechanical distance between the tip of the probe and the point on the sample interacting with the tip) is minimized so that uncertainties arising from deformations or alignment errors in the structure are kept to a minimum. To achieve this objective, the integration into the metrology loop of translation stages for the coarse alignment of the sample in both the plane and along the -axis has been avoided. Furthermore, the two major components of the metrology loop, the metrological frame and the three axes translation stage, are precision engineered from SuperInvar, a FeNiCo alloy with a thermal expansion coefficient of at 20°C19 and a temporal stability over a period of a day of part in (20). The metrological frame is axially symmetric around a vertical axis that runs through the tip to maintain the on-axis tip position even when the frame expands or contracts. Where possible, components are kinematically mounted, again to minimize distortions due to thermal expansion and to minimize displacement when the instrument is reassembled. Finally, the solid, rigid structure of the metrological frame minimizes the effects of ambient vibrations.