Thermal flow-rate sensor for liquids and gases

摘要

A sensor for continuous thermal measurement of gaseous and liquid media comprises of heated wire, as a heat-source which delivers heat to the through-flowing material (medium), as well as a temperature sensor which is mounted at a given distance from the heat-source in the direction of flow of the medium and registers the heating of the medium. A time-varying temperature signal is impressed on the flowing medium by means of time-modulation of the temperature signal at the heat source and is transported with the flow of medium and is recorded by the temperature sensor, whereby a measure for the flow is obtained for the propagation time of the AC temperature signal, with the required accuracy achieved by evaluating the weak sensor signal by means of a phase comparison process between the transmitter and receiver.