Extech AN340-NIST Datalogging Anemometer Psychrometer automatically datalogs up to 12,000 readings and includes a telescoping vane sensor, measures Air Velocity, Air Flow, Air Temperature, Humidity, Dew Point and Wet Bulb. Extech AN340-NIST Datalogging Anemometer Psychrometer also includes data hold function and auto shutoff, built in PC interface, and allows selection of data sampling rate from 1s to 4 hr, 59 min, 59 s.