Nikon AC-2S Auto Level

An automatic level, self-levelling level, or builder's auto level includes an internal compensator mechanism (a swinging prism) that, when set close to level, automatically removes any remaining variation. This reduces the need to set the instrument base truly level, as with a dumpy level.An auto level is an optical instrument that can be used to establish or verify points on the same horizontal plane, and it has an internal mechanism that eliminates variation and inaccuracy from measurements.A dumpy level, automatic level, leveling instrument is an optical instrument used to establish or verify points in the same horizontal plane. It is used in surveying and building with a vertical staff to measure height differences and to transfer, measure and set heights.The automatic level has a compensator mechanism that uses a combination of fixed prisms or mirrors and a moving prism suspended on a pendulum to give a horizontal reference. When correctly set up the compensator will ensure that the ray of light through the centre of the reticule is exactly horizontal.