Ultra-precision pneumatic measurement technology and its applications

Non-contact pneumatic measurement technique is an important method in the dimension measurements of machine parts. In order to realize ultra-precision dimension measurement of machine parts in the in-process inspection systems, the new type of air-pin pneumatic-electronic sensor has been developed by the authors. Air-pin pneumatic-electronic sensor and its system consist of micro-orifice like a needle that is formed by high-pressure gas-flow through a micro-hole, micro-gas-routine, pressure sensor and micro-controller. Compressed air is pumped into the main chamber, through the main orifice and flows out through the measuring orifice. The backpressure chamber with main orifice and measuring orifice is passed by the high-pressure air flow from a supply at constant pressure P-C to atmosphere P-0. Any variation in the separation S between measuring orifice and the plate of the work piece measured will cause an alteration in the backpressure P-x in the chamber. Although the function of air-pin pneumatic-electronic sensor is nonlinear, a segment on the function curve as a linear measurement range in which the measurement sensitivity is constant approximately has been chosen. Air-pin pneumatic-electronic sensor with 10mum in the measurement range, and its measurement accuracy is better than 0.1mum. It has been used in a project of measuring hemispherical surface of an air bearing of astronautic gyro. It can also be used to measure different three dimension contour in precision engineering.