A Constant Temperature Wind Component Meter and its Performance Characteristics

Abstract

A constant temperature-difference, hot thermocouple anemometer and component meter have been developed from a previously existing instrument. The constant temperature-difference mode of sensing eliminates the need for correction of the effects of temperature in total wind sensing, and of wind in angle sensing. This feature also provides high sensitivity even in high wind. The new model incorporates a fast response temperature measurement circuit and is capable of determining the flux of heat and momentum near the surface. Response characteristics of the wind measuring system are those of a second order system. A setting of amplifier gain which makes damping ratio 0.7 and natural frequency 2.5 cps gives undistorted frequency and phase response up to 1 cps. Above this frequency, distortion is specified by a known transfer function of the first order in which a time constant specifies complete characteristics. For the model used in this study the time constant was 0.115 sec. The result of a field experiment confirmed the analysis of the performance characteristics.