Mass flow controllers are devices used to measure the control of gas flow. They are designed to control a specific type of gas by that gas’s range and rate of flow. They are used wherever accurate measurement and control of a mass flow of gas is required without relying on the flow pressure change and temperature change in a given range.MFCs control the rate of flow based on a given set point, which can be changed from 0 to 100 percent.It can operate to control one type of gas (analog) or more than one type of gas (digital).
A mass flow controller works fairly simply for its process.All contain an inlet port, an outlet port, a mass flow sensor and a proportional control valve.The flow of gas is divided by the sensor, where the mass flow is measured, and the bypass, where the flow passes.The latter is designed so that any flow through the sensor and bypass is proportional to the flow range.The former delivers an output voltage proportional to the gas flow circulating throughout the controller. This is where the electronics board comes in.It amplifies the sensor signal so that the output gives a signal that is proportional to the total flow in the mass flow controller.
The volumetric gas flow rate differs depending on temperatures and pressures.Gas is mostly measured in cubic centimeters per minute.Ideal gas laws are sometimes used in order to convert from units of mass flow to volumetric flow.Density highly depends on temperature and pressure so these must be constantly checked.
The supply gas that enters a mass flow controller must be within a specific pressure range.If the pressure is too high, it could result in erratic flow.If the pressure is too low, it will cut off the MFC and keep it from reaching the set point.For this reason, it is important to make sure the gas is precisely in the right pressure range and that the MFC’s set point can be between 10 and 90 percent.