Measurement of draught using ultrasonic air transducers

Draught currents in buildings and houses in cold weather are a common problem that is often caused by dampness and/or poor insulation of windows and walls. The extent of the draught is dependent on the temperature gradient between the inside and outside of the building, the thermal resistance of that part of the building exposed to the outside atmosphere, and also on the nature of heating and ventilation provided. However, significant draught currents are still very slow, which causes problems in measurement. In this paper, work carried out in developing an ultrasonic sensory system capable of measuring low air flow velocity in the range of ∼1 cm/s is presented.