The Davis Instruments Turbo Meter Wind Speed Indicator measures wind speed from 0 - 99 MPH and is accurate to +/- 3%. The rotation of the freely turning turbine on the Turbo Meter, suspended on sapphire jewel bearings, is sensed by aninfrared light beam. The resulting signal is processed electronically. The display is large and bright forexcellent viewing in full sun or dark conditions. The Turbo Meter Wind Speed Indicator includes a Auto Power-Off feature, is compact in size and lightweight. Wrist lanyard, protective case included.