Abstract: A flow meter includes a heater for heating a fluid flow along a membrane. A temperature difference is measured between and upstream point and a downstream point. There are additionally provided one or more strips of material having a relatively high heat conductivity. Strips that are substantially perpendicular to the flow direction direct heat from the heater to the sides of the membrane, causing a large proportion of the heat that would otherwise drive heat flows to be dispersed and decreases inaccuracies or bias in the measured flow rate. Strips of material that are provided parallel to the flow direction act to direct heat from the heater along the direction of flow. This increases the proportion of heat that flows along this axis and guides the flow and hence reduces the proportion of heat available to drive heat flows that cause inaccuracies and bias in the measured flow rates.