Capillary tube thermal mass flow meters directly measure the mass flow rate of clean gases and gas mixtures in lower flow ranges. A capillary tube thermal mass flow controller adds an integrally mounted flow control valve to the flow body of the mass flow meter and bom monitors the mass flow rate and controls it to be equal to a set-point value selected by the user.
This paper describes capillary tube mass flow meters and controllers for use in general purpose industrial and laboratory applications and in the fabrication of semiconductor devices. It provides a detailed description of the major components— -flow body, flow conditioner, bypass, capillary sensor tube, control valve, and electronics. Flow ranges and specifications for which this technology is best suited are presented. The paper explains the principle of operation; describes gas conversion factors mat provide multi-gas capability in a single instrument; lists best practices for users, including the selection, installation, and operation of the instruments; and concludes with a discussion of preferred methods of flow calibration.
Keywords: flow meter, gas flow meter, mass flow meter, mass flow controller, thermal mass flow meter, capillary tube thermal mass flow meter, capillary tube thermal mass flow controller.
Capillary Tube Thermal Mass Flow Meters & Controllers - A User`S Guide - White Paper