an anemometer and method for analyzing fluid flow is described . in one embodiment , a transistor sensor is heated by applying power to cause its base - emitter junction to rise from an ambient first temperature to a second temperature . the power is removed , and the vbe is measured at intervals as the junction cools . the vbe equates to a temperature of the junction . the temperature exponentially decreases , and the time constant of the decay corresponds to the fluid flow velocity . a best fit curve analysis is performed on the temperature decay curve , and the time constant of the exponential decay is derived by a data processor . a transfer function correlates the time constant to the fluid flow velocity . the transistor is thermally coupled to a metal rod heat sink extending from the package , and the characteristics of the rod are controlled to adjust the performance of the anemometer .