1.1 This part of ISO 17713 describes wind tunnel test methods for determining performance characteristics of rotating anemometers, specifically cup anemometers and propeller anemometers. 1.2 This part of ISO 17713 describes an acceptance test and unambiguous methods for measuring the starting threshold, distance constant, transfer function and off-axis response of a rotating anemometer in a wind tunnel. Note that when transferring values determined by these methods to atmospheric flow, there is a difference between anemometer performance in the free atmosphere and in the wind tunnel.