the flow of a fluid of unknown composition is measured by leading the fluid over a first temperature sensor , a heater and a second temperature sensor . the temperature difference dtp between the temperature sensors is measured , as well as the temperature t of at least one of them . in addition , calibration data is used to store the temperature tref of a known reference fluid . the offset t − tref at a given temperature difference dtp is a direct measure of the composition of the fluid and allows to retrieve any parameter depending on the same .