Improvements to NIST׳S air speed calibration service

We discuss five significant improvements to the Air Speed Calibration Service conducted by the National Institute of Standards and Technology (NIST): 1. Reduced-uncertainty calibration of the secondary standard [Laser Doppler Anemometer, (LDA)] using a spinning disk, 2. Reduced-uncertainty LDA measurements that account for the position-dependence of the air speed in the test section and for window effects, 3. Improved repeatability, precision, and ease of calibrations by using automated data acquisition and PID air speed control, 4. optical character recognition data acquisition system for anemometers lacking electrical outputs, and 5. up-to-date uncertainty budget of the LDA. Also, we present the results (with uncertainties) of Pitot tube calibrations.