This paper presents the design and working principle of a pneu-pin sensor based on a gas path with differential pressure,
and the study on its curve-baffle characteristics. The measurement range of the sensor is about 32 &mgr;m, with a resolution
of 0.03 &mgr;m and less than an uncertainty of 0.3 &mgr;m. It is found through research on the curve-baffle characteristics with
different curvature radius of steel balls that the axis of the pneumatic probe does not need to go through the geometric
centre of work-piece, and so, the high accuracy positioning of the work-piece is avoided. Therefore, the pneumatic
measurement technology researched in this paper can be applied to high accuracy non-contact dimension of
measurement of different curvature radius of work-pieces.