Design, construction and characterization of pneumatic system for measurement of roughness

Abstract

This article aims to present the results obtained from the design, construction and characterization of a pneumatic flapper-nozzle amplifier, employed in the measurement of average surface roughness. In the construction of the sensor, low cost materials were used and most pieces were obtained by machining. The data acquisition was performed through PC, using an Arduino interface board. The nonlinear mathematical model of the sensor is based on equations of perfect gas flow through an orifice and the continuity law for a control volume. The characterization of physical parameters obtained through laboratory techniques based on the transient response of the gas pressure in the pressurization and depressurization processes of constant volume chambers, using computational tools for adjusting experimental curves. The validation of the model was based on the specifications of transient response that presents a dynamic system for a step input. For the measurement of the roughness, the mathematical model of average roughness, Ra, was used, and the measured data by the sensor were obtained in sandpapers from P1000 to P2000 size, with reference for validation values of average roughness indicated by the FEPA standard.