Mass flowmeters and controllers (MFMs and MFCs), sometimes called thermal mass flowmeters, are electronic devices that indicate flow by measuring the thermal properties of a given gas.
In most commonly used MFMs, the gas flows through a precision tube that has a precise sampling or bypass capillary tube running in parallel with the main flow. The sampling tube samples or bypasses the primary flow at a ratio of approximately 100 to 1.
The bypass flow is passed through a controlled-heating element, which imparts a known amount of heat (i.e., energy) into the gas stream. Knowing the temperature of the gas, before and after the heating element, together with the thermophysical properties of the gas, the main flow through the meter can be accurately calculated.
Volume 5A, Thermal Spray Technology → Thermal Spray Processes and Coatings →
Process Control and Control Equipment → Gas Flow Measurement and Control
