Analysis of air gage inaccuracy caused by flow instability

In the paper, the air gaging system has been examined. The length measurement with pneumatic devices equipped with piezoresistive pressure sensors has been described. The conditions of the air expansion in the flapper–nozzle area would affect the stability of the air pressure in the measuring chamber, which is registered by pressure sensor. As a result, the indications of the length are unstable, too, even though displacement remains unchanged. Those deviations of measurement signal have been described, and recommendations how to reduce their influence on the measurement results have been proposed.