Low speed and turbulence measurements based on composite hot-film technology

The paper studies the composite hot-film test method used to measure the air veloc-ity and turbulence at low speed.The output sensitivity of the air velocity measurement is general-ly low in wind tunnel tests.In order to improve the sensitivity of the hot-film sensitive probe when the velocity is very slow,the temperature difference between the hot-film and the airflow is enhanced.The velocity and turbulence of the low speed airflow can be accurately measured even when it is under 2m/s.In order to correct the output of the hot-film sensitive probe influenced by the gas temperature,the methods of temperature compensation and compensation circuit are studied.A special circuit is designed to obtain the accurate control of temperature difference.By matching the structune,size and components of the hot film reasonably,the hot film sensitive probe is miniaturized.Using the MEMS technology,good frequency response of the probe is achieved by reducing the size of the thermal resistances and measurement resistances.Test results show that the composite hot-film sensitive probe can satisfy the requirement of the low speed and turbulence measurement.