Sub-miniature five-hole probe calibration using a time efficient pitch and yaw mechanism and accuracy improvements

A five-hole probe is a proven aerodynamic tool for the accurate measurement of flow fields, but is traditionally difficult to calibrate manually in an acceptable range of pitch and yaw angles. With advancements in computer technology, it is possible to improve the calibration process that is made up of tedious and repeating angular pitch and yaw angle movements. This paper proposes a way to increase the accuracy of measurements. The proposed approach uses computer automation, a mechanical pressure scanner, and precision rotary tables to significantly reduce the amount of time required to complete the calibration sequence. A five-hole probe is fastened to a precision calibration mechanism in a wind tunnel test section. This mechanism varied the pitch and yaw angle of the probe accurately via two computer controlled rotary tables. This approach allowed for a much greater degree of accuracy and a way to increase the number of data points taken, better defining the non-linear portions of the calibration maps. The scanivalve system minimized the number of transducers required from seven to one. While it takes more time than having multiple transducers, this approach lowered the overall equipment costs and helped to reduce measurement errors. The data acquisition device provides an interface between the rotary table stepper controllers, the scanivalve controller, and the transducer. A LabVIEW interface was then used to control all of the devices, while simultaneously retrieving data from the transducer and turning it into the coefficients needed to make the calibration map. The program allows for a degree of flexibility, allowing the user to choose the range of angles and the degrees between each point.