FTM06D is based on the principle of thermodynamics, it can measure air velocity and volume, there are 2 temperature sensors inside the probe - one for temperature measurement, the other serves as the measurement conveyor after heating. The temperature difference between the two is taken as the basis for measuring the flow rate. When the ambient flow rate increases, the temperature difference decreases. The flow rate can be measured by these two sensors due to the temperature difference, which is converted into standard signal output after processing. It is an all-metal body suitable for various pipe diameters.