In our Latinamerican countries, people have rarely developed about medical control systems based in sensors (transducers) and actuator done in our environment. This has motivated the present work. In medical applications such as breathing systems the hot wire flow sensors are being used actually. Taking advantage of the sensor thermal convection, we can achieve a rapid operation using a smaller than 250 ms sampling time. This study was made based in stuff such as Nicrom (100 um), Nickel-Titanium alloy (37 and 100 um) and Platinum (21 um), that use the "King's Law" that relates Thermal Convection with Electrical Power; this law may detect flow changes through voltage changes when the temperature is constant; showing succesfully an alternative of flow sensing in any given conditions. The flow calibration system used in this work is based in the principle of the RC discharge, using the constant compliance of a rigid water column, where the pressure gets a lineal shape with a pressure step source and a 450 us sampling time for this two signals: flow and pressure.