Realization of Constant Voltage Anemometer Using an Alternative Signal Conditioning Circuit

Abstract

Anemometric method is the most accurate and reliable technique for air velocity measurement. In present work, a voltage follower based circuit is proposed, and a low-cost sensor (tungsten filament) is chosen to perform Constant Voltage Anemometer (CVA) operation for air velocity measurement. For performing the real-time experiment, a wind tunnel featuring a rectangular section (test section I) and a circular section (test section II) with a provision for low-cost sensors and a reference Hot Wire Anemometer (HWA) was fabricated. The measurement is repeated multiple times for various air velocities in the range of 3 m/s to 12 m/s. The estimated ‘pdr’ value (ratio of the power dissipated in the sensor, Pw to the difference between heated sensor resistance, Rw and the sensor resistance at ambient temperature, Ra), considered as new output voltage, is analogous with the output voltage (Vo) of the proposed circuit. The range of ‘pdr’ in test sections I and II is 0.033 mW/Ω to 0.867 mW/Ω and 0.0062 mW/ῼ to 0.1059 mW/Ω, respectively. Similarly, overheat ratio, OHR (ratio of the difference between heated sensor resistance, Rw and the sensor resistance at ambient temperature, Ra to the sensor resistance at ambient temperature, Ra) estimated, is also found to be analogous with the change in temperature (difference between the temperature of the heated sensor Tw and the ambient temperature Ta). The range of OHR in test sections I and II is 0.709 to 0.660 and 0.678 to 0.647, respectively. Uncertainty analysis is carried out for the proposed voltage follower based CVA measurement system and the expanded uncertainty with a 95% confidence level is obtained as 0.54 for the whole range of air velocity measurement.