Abstract: A hot film dual element fluid flow sensing device has its two hot-film sensors arranged in-line on an elongate support. A flow deflection collar is situated midway on the support between the two flow sensors and deflects the flow away from the sensor situated behind the collar. Underlying the sensor films of the two flow sensors and electrically insulated from those sensor films is an electrical heater. In operation of the device, the heater and the sensor films are electrically heated to about the same temperature to inhibit heat transfer therebetween. Because of that arrangement, the device responds rapidly to changes in fluid flow because virtually all the heat lost by the sensor films is transferred directly into the surrounding fluid.

Abstract: A fluid flow sensor apparatus for determining speed, mass flow and direction of motion relative to a fluid in which the sensor is immersed. The sensor is constructed of at least two spaced apart resistive electrical conductors which are mechanically supported to provide a degree of thermo isolation between the conductors in order to effect the determination of instantaneous fluid flow direction. A pair of the conductors is joined so that the flow around separate conductors is avoided so as to force one conductor to be a leading edge to the flow stream and the other conductor to be a trailing edge, with separate flow passing over the conductor pair. The electrical conductors can be wires or they can be metallic or resistive films which are deposited on a supporting body. The conductor is made of a material which exhibits a change in the electrical resistivity as a function of temperature.