Correction of the metrological properties of the pneumatic length measuring gauges through changes of the measuring nozzle head surface shape

In this paper, the geometry of the measuring nozzle head surface used in an air gauging system has been examined. The concept of conical correction of the surface in order to influence the metrological properties of the air gauge has been described. Geometrical correction has a substantial impact on the conditions of the outflow and the metrological properties of the air gauge. The outflow surfaces for a corrected nozzle have been calculated for different slots, and the transition point has been defined for the smallest outflow surface. The analysis of possible static characteristics enabled us to examine the influence of other parameters like inlet nozzle diameter or multiplication on the linearity. As a result of analysis, the method of the measuring head nozzle profile calculation has been presented. The experimental verification of the concept of conical surface correction in order to influence the metrological properties of an air gauge has been described. Dozens of corrected measuring nozzles have been manufactured and undergone experimental research. Comparative analysis of the static characteristics gained enabled us to examine the influence of other parameters such as inlet nozzle diameter or multiplication on the linearity and to contrast the results with the theoretical expectations. (C) 2010 Elsevier Ltd. All rights reserved.