Metrological characteristics 4.1 Appearance The appearance and structure of the testing machine should be intact. The testing machine should have a nameplate, manufacturer, model, factory serial number and date, certificate, etc. 4.2 The wind speed range in the wind tunnel is (3±0.3)m/s. 5 Calibration conditions 5.1 Environmental requirements 5.1.1 Ambient temperature: (23±5)℃,; Relative humidity: (40～70)% 5.1.2 The surrounding environment should be free of cold and heat sources, vibration, electromagnetic interference, pollution and Corrosive gases, etc. 5.2 Calibration equipment: 5.2.1 Anemometer: Measuring range (0.5～4)m/s, MPE: ±0.2m/s.