| Description |
This paper describes the design and characterization of a novel, miniature, twodimensional anemometer that utilizes an optical fiber, laser diode, and position sensitive detector (PSD). The fiber functions as a cylindrical cantilever beam with the fixed end secured to the side of an aerodynamic shell, while the free end of the fiber extends perpendicularly into the flow stream. Light transmitted by a laser diode shines through the free-end of the fiber and illuminates the surface of the PSD chip, which is flush-mounted to the other side of the sensor shell. The approach flow induces a drag force on the fiber, causing it to deflect, thereby displacing the light beam on the face of the PSD chip. The location of the beam centroid is output from the anemometer circuit as two analog voltage signals, which may be directly related to the approach velocity through a calibration curve. The currentgeneration prototype consists of a 125 //m diameter, 20 mm long silica fiber, with the capability of measuring turbulent velocities at frequencies up to about 220 Hz and velocity magnitudes up to about 15.5 m/s ±0.5%. Experiments were performed to measure long-term drift, sensitivity to ambient light conditions, thermal effects, and frequency response. Numerical simulations were also performed to examine flow disturbance in the immediate vicinity of the fiber due to the geometry of the sensor shell. Importantly, the use of fiber optic technology allows for a relatively inexpensive, lightweight, low-power design. The intended application of the present anemometer is Meteorology; and atmospheric science research. |
