On the basis of theoretical analysis on the pneumatic measurement, a new type of pneumatic measuring instrument was developed.

Aimed at the spheric face of smaller diameter and sphericity of a higher-precision, a new method called "pneumatic measurement" is used in the area of sphericity error measurement.

Based on a comparison of various current flatness measurement methods, this paper proposes to utilize pneumatic measurement in the flatness measurement system for the brakes 'steel back.