Massavirtaussäädin

Massavirtaussäädin, known in English as a mass flow controller (MFC), is a device that measures and controls the mass flow rate of a fluid. It is distinct from a volumetric flow controller, which measures and controls volume. Mass flow controllers are crucial in applications where precise control of substance quantity is necessary, regardless of changes in pressure or temperature that would affect volume.

The fundamental operation of a mass flow controller involves sensing the mass flow rate and then adjusting a valve to maintain that rate at a setpoint. Various sensing technologies are employed, with thermal mass flow sensors being the most common. These sensors typically work by heating a portion of the fluid stream and measuring the amount of heat carried away by the flow. This heat transfer is directly proportional to the mass flow rate.

Once the mass flow is sensed, the controller compares it to the desired setpoint. If there is a deviation, an electronic signal is sent to a control valve. This valve, often a proportional solenoid valve or a stepper motor-driven valve, is then actuated to increase or decrease the flow until the measured mass flow rate matches the setpoint.

Mass flow controllers find wide application in semiconductor manufacturing, chemical processing, gas mixing systems, scientific research, and medical equipment. Their ability to ensure consistent and accurate delivery of gases and liquids is vital for process repeatability and product quality. The precision and reliability of MFCs make them indispensable tools in many advanced industrial and scientific fields.