In-situ swinging arm calibration for hot-film anemometers

Abstract

A method of calibration for hot-film anemometers is presented. A swinging arm that moves under the influence of gravity serves as both a calibration mechanism and a probe support. The velocity of the probe is found by differentiating the angular position history of the arm and multiplying it with the arm length. Limitations on the quality of calibration data while the arm is accelerating are discussed. The hot film voltage output is then matched to the velocity to find the two constants in King's law. The calibration was tested by taking velocity profile measurements in a laminar boundary layer. The results of these compared well to the Blasius profile.

Hot-Wire Calibration at Low Velocities: Revisiting the Vortex Shedding Method

“…For the calibration of hot wires at low velocities, several calibration techniques have been developed, such as modified calibration jets [8], the laminar pipe-flow method [9], the rotating disk method [10], methods exploring wall proximity effects [11,12], and a variety of methods utilizing a moving [13][14][15] or swinging probe in still air [16,17], as well as the vortex shedding method [12,[18][19][20][21]. In the present paper, we will focus on the vortex shedding calibration method, which has also been suggested in classical hot-wire literature, as, for example, in Perry [5] or Bruun [6].…”