RESUMO
Esta pesquisa teve como objetivo desenvolver um anemômetro de fio quente para operar à temperatura constante usando-se, como elemento sensível, filamento de tungstênio de lâmpada incandescente, como braço da ponte de Wheatstone. Um circuito eletrônico foi construído e testado, permitindo controlar a tensão no sensor e restaurar o equilíbrio da ponte de Wheatstone em processos de troca de calor pelo sensor. Os resultados mostraram que a corrente elétrica e a temperatura de operação do sensor, mediante compromisso entre vida útil e sensibilidade, foram de 160mA e 140°C, respectivamente; a calibração com o sensor no circuito ponte de Wheatstone mostrou sensibilidade para medir a velocidade do ar no intervalo de 0,00 e 5,00m.s-1 e que o circuito eletrônico apresentou saturação para velocidades do ar inferiores a 0,50m.s-1.
Palavras-chave:
anemômetro de temperatura constante; sensor de tungstênio; ponte de Wheatstone
ABSTRACT
This research was carried out with the purpose of developing a hot-wire anemometer operating at constant temperature, using as a sensitive element a tungsten filament fan incandescent lamp as a Wheatstone bridge arm. An eletronic circuit was constructed and tested to control the voltage in the sensor and to restore the equilibrium of the Wheatstone bridge in the transfer of heat by the sensor. The results showed that the sensor's eletrical current and temperature of operation, considering useful life and sensibility, was 160mA and 140ºC, respectively. The calibration with the sensor in the Wheatstone bridge circuit showed sensibility to measure the air velocity in the interval between 0.00 and 5.00m.s-1. It also showed that this eletronic circuit presented saturation in measuring the air velocity lower than 0.50m.s-1.
Key words:
constant temperature anemometer; tungsten sensor; Wheatstone bridge
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Parte da tese de mestrado do primeiro autor. Fone (031)899-2734, Viçosa, MG
REFERÊNCIAS BIBLIOGRÁFICAS
- CHAMPAGNE, F.H.; SLEICHER, C.A.; WEHRMANN, O.H. Turbulence measurements with inclined hot-wires. Part 1. Heat transfer experiments with inclined hot-wire. Journal Fluid Mechanics, v.28: p.153-175, 1967.
- DAVIS, M.R. The dynamic response of constant resistance anemometer. Journal of Physices E.: Scientific Instruments, v.3: p.17-20, 1970.
- LOMAS, C.G. Fundamentals of hot wire anemometry Cambridge, The University of Cambridge, 1986. 211p.
- MILLER, I.S.; SHAH, D.A.; ANTONIA, R.A. A constant temperature hot-wire anemometer. Journal of Physices E.: Scientific Instruments, v.20: p.311-314, 1987.
- NATIONAL ASSOCIATION OF FAN MANUFACTURES NAFM. Standards, definitions, terms and test codes for centrifugal, axial and propeller fans. 2.ed. Detroit, 1952. (Bulletin, 110).
- OWER, E.; PANKHURST, R.C. The measurement of air flow. 5.ed. New York: Pergamon Press, 1977. 374p.
- PEARCY, R.W.; EHLERINGER, J.R.; MOONEY, H.A.; RUNDEL, P.W. Plant physiological ecology; field methods and instrumentation. New York: Chapamn and Hall, 1989. 442p.
- PERRY, A.E. & MORRISON, G.L. A study of the constant temperature hot- wire anemometer. Journal of Fluid Mechanics, 47: 577-599, 1971.
- PLATT, R.B.; GRIFFITHS, J.F.. Environmental measurement and interpretation. 3.ed. New York: Robert E. Krieger, 1972. 231p.
- ROSENBERG, N.J.; BLAD, B.L.; VERMA, S.B.. Microclimate; the biological environment 2.ed. New York: John Wiley & Sons, 1983. 495p.
- WATMUFF, J.H. Na investigation of the constant temperature hot-wire anemometer. Experimental Thermal and Fluid Science: 1995.
- WEIDMAN, P.D.; BROWAND, F.K. Analysis of a simple circuit for constant temperature anemometry. Journal of Physices E.: Scientific Instruments, v.8: p.533-560, 1975.
Datas de Publicação
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Publicação nesta coleção
May-Aug 1998
