The time response of a wind tunnel pressure measuring system, comprising a pressure transducer of fixed volume and a length of capillary tubing, is analysed and the results compared with experiments. It is shown that the approximate analysis of Kendall (1958), in which the friction losses at any given time are assumed equal to the steady state losses, has a wide range of validity, provided the L/R ratio for the capillary tube is large and the inlet and exit losses are included as equivalent lengths of the capillary tube.