1) Dimensional instrument 2) Measuring device 3) Measuring instrument 4) Measuring system 
A spherometer is an instrument for the precise measurement of the radius of a sphere. Originally, these instruments were primarily used by opticians to measure the curvature of the surface of a lens. The usual form consists of a fine screw moving in a nut carried on the centre of a small three-legged table or frame; the feet forming the vertices o...
instrument measuring curvature
• (n.) An instrument for measuring the curvature of spherical surface, as of lenses for telescope, etc.
Sphe·rom'e·ter noun [ Sphere + -meter : confer French sphéromètre .] (Physics) An instrument for measuring the curvature of spherical surface, as of lenses for telescope, etc. 
Type: Term Pronunciation: sfē-rom′ĕ-tĕr Definitions: 1. An instrument to determine the curvature of a sphere or a spheric lens. See: Geneva lens measure
[n] - a measuring instrument for measuring the curvature of a surface
noun a measuring instrument for measuring the curvature of a surface