Thermal Mass Flowmeters  use the temperature field changes generated when the fluid flows through a pipe heated by an external heat source to measure the mass flow of the fluid, or when the fluid is heated A flow meter that measures the relationship between the energy required for fluid temperature to rise a certain value and fluid mass to measure fluid mass flow.

They are generally used to measure the mass flow of gas. It has the characteristics of low pressure loss; large flow range; high precision, high repeatability and high reliability; no moving parts and can be used for monitoring and controling of extremely low gas flow. There is a long history of using the heat (or temperature) change of the heated fluid to measure the mass flow of the fluid.