Icing Wind Tunnel Tests on the CSIRO Liquid Water Probe

Abstract

Wet wind tunnel tests have been Performed on several versions of the CSIRO probe designed for the airborne measurement of liquid water content. Four different controller units and 17 different Probe sensors (including half-size and shielded versions) were tested. Even with tests conducted under extreme conditions, differences in response for all units were always less than 15%, except for the shielded units which needed to be operated at least 60°C better than the unshielded ones to yield the same output. Probe measurements with the unshielded sensors were typically within 5% and always within 10% of the tunnel values which were determined from icing cylinder measurements. The short length probes performed equally as well as the standard length ones and have certain operational advantages, such as Water robustness and the ability to operate at higher liquid water contents for a given supply voltage. Changing airspeed from 15 to 100 m s?1 and ambient temperature from ?28°C to +10°C produced no measurable effect on any probe response, whereas grossly overdamping the probes via incorrect offset voltages could reduce the apparent output sensitivity by as much as 50%.