A digital wind gust recorder

Abstract

The instrument was a byproduct of an undergraduate final year project on wind power which was carried out by the Department of Mechanical Engineering of the University of Liverpool. The windmill test site was on an exposed, rocky island where there was no history of weather recording but a long tradition of violent winds. Field experience during the winter months suggested that corrosion fatigue arising from wind buffeting and salt spray would rank equally with maximum wind pressure as criteria of failure and if modern materials, so convenient for forming aerodynamic surfaces, were to be used then limited life concepts would need to be considered. This called for more knowledge of wind variations at the test site. A complete wind spectrum taken on chart recording instruments would have been ideal but since such such refined devices were not available the instrument to be described was designed. The only wind measuring instrument which was available was a rotating cup anemometer. This supplied an alternating voltage proportional to its rotational speed. It also operated a gear driven microswitch which could give an integrated “miles of wind” reading on an electromagnetic counter. Briefly the e.m.f. generated by the anemometer (Fig. 1) was matched against a pre-set voltage corresponding to the required gust velocity. When this was exceeded an appropriate counter was operated. Only the rising e.m.f. was significant. The subsequent fall was ignored. Initially three stages were incorporated which reported the gusts rising through forty, fifty and sixty knots, respectively. These recorded on separate counters. All basic settings were based on pitot-static speed determinations in a wind tunnel.