The flow velocity calibration system using ultrasonic anemometer and LDV

Abstract

An anemometer calibration system in the range of 3 to 30 m/s has been developed. This system consists of an LDV calibrator, an LDV for a transfer standard and a wind tunnel, which uses an ultrasonic anemometer installed on the side walls of the test section as a reference standard. An anemometer under test is placed at the center of the wind tunnel test section and the anemometer output is calibrated against the ultrasonic anemometer, which has been beforehand calibrated using the LDV, which is also calibrated by the LDV calibrator. Repeated tests of this system showed that precise adjustment of the LDV processor threshold level is necessary to avoid an error due to a misalignment of the LDV optics. It is also suggested that when the LDV is calibrated by using the LDV calibrator, the condition including the filter range and the threshold level should be set as same as possible to that used to calibrate the ultrasonic anemometer.