MODEL 27106D GILL PROPELLER ANEMOMETER JANUARY 2003 MANUAL PN 27106D-90 R. M.
MODEL 27106D GILL PROPELLER ANEMOMETER INTRODUCTION The Gill Propeller Anemometer Photochopper is a low threshold precision air velocity sensor employing a fast response helicoid propeller. The instrument uses a high quality optical photo chopper which converts propeller rotation to a square wave signal whose frequency is linearly proportional to air velocity. The output signal is the same regardless of propeller rotation.
When the propeller is used for measuring vertical wind component, users may want to apply a 1.25 multiplier to the output signal. This may be done numerically in data processing operations or electronically in the signal conditioning. Using the multiplier brings the anemometer output signal within ±3% of the cosine response for elevation angles between -30 and +30 degrees. Since the standard deviation of wind elevation angle in open terrain rarely exceeds 12 degrees, 98% (2.