A straight needle-probe for the measurement of blood velocity

Abstract

A thin-film gauge to measure instantaneous fluid velocity is described. The element, which consists of a platinum thermometer, is cemented into a straight hypodermic needle of 075 mm outside diameter and heated electrically to 10 degc above ambient temperature. Heat is removed by forced convection and is related to instantaneous velocity. Calibrations of the probe in water for various angles of inclination to the stream are obtained and a simple method of detecting reversed flow is described. Identical calibrations in water and blood are found, despite a fourfold difference in kinematic viscosity, and an explanation of this effect is advanced.