Comparison of the Dynamic Response of Calorimetric and Hot-Film Flow Transducers

The dynamic behavior of micromachined calorimetric flow sensors for gaseous fluids was investigated both, experimentally and by computer-numerical simulations. The study covers the influence of geometry parameters on sensitivity and response time as a function of the flow velocity. Using FEM analyzes, the flow dependence of the temperature of the thin-film heat source becomes accessible, which is representative for the response of hot-film transducers. At low flow velocities, calorimetric sensors respond notably faster than comparable hot film sensors to step-like changes of the fluid velocity. For large flow steps, where temperature-controlled operation is mandatory, the hot-film flow sensor promises a slightly faster response.