Development of a flow meter for instantaneous flow rate measurements of anaesthetic liquids

An instrument has been developed for instantaneous flow rate measurements of anaesthetic liquids. For periodically time-varying flows, the instantaneous flow rate is reconstructed from the axial velocity time series measured on the centre-line of a pipe. The theoretical background for the method is given and it is demonstrated that fast variations of flow rate can be measured. The instrument is based on a laser Doppler anemometer (LDA) to record the instantaneous velocity on the axis of a capillary; an ultraviolet laser permits velocity measurements with good signal-to-noise ratio from tracer particles in the submicrometer range present in anaesthetic liquids.