Flow gas transducer on basis of a hot wire with a nickel-titanium alloy in its flow calibration system

In our Latin American countries, little development has been carried out on medical control systems based on sensors (transducers) and actuators for our environment. This has motivated the present work. In medical applications such as breathing systems, hot wire flow sensors are already in use. 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 on material such as Nichrome (100 μm), nickel-titanium alloy (37 and 100 μm) and platinum (21 μm), 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 successfully an alternative for 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 μs sampling time for these two signals: flow and pressure.