An Improved Sonic Anemometer—Thermometer

Abstract : A prototype sonic thermometer has been developed for use in conjunction with a sonic anemometer previously developed by Stanford Research Institute (SRI). The sonic thermometer was developed to furnish an analog signal representing air temperature and to automatically provide a correction to the sonic anemometer's representation of the horizontal windpseed for error due to temperature changes in the air. A portion of the sensing probe for the sonic anemometer identically serves as the sensing unit for the temperature measurement. The sonic thermometer utilizes signals from the transmitter and from each of two diametrically opposite receivers located in the horizontal plane. In the design analysis, consideration was given to temperature measurement errors arising from sources such as air velocity, air pressure and humidity fluctuations, theoretical approximations, and stability of the measuring instruments. The absolute accuracy of the sonic thermometer is approximately within one degree Kelvin. Resolution is approximately 0.05K. (Author)