the process for the construction of a micro - thermocouple sensor designed to be incorporated in a mass flow meter for the circulation of gaseous fluids , including of the following steps : deposit of an insulating layer of several microns by electron gun on the sensor tube , then the deposit of the components of the thermocouple , by the electron gun , through the nickel masks , at a residual pressure lower than 10 ′ torr , at a thickness of several thousand angstroms . then annealing of the capillary tube for one hour , then the mounting of a heating element on the capillary tube treated in this manner .