A mass flow controller is a device that controls a gas flow rate automatically depending on the preset speed of the flow sent as a signal without any interference from pressure changes.
Generally, flow rates are categorized as either mass flow or volumetric flow. Changes in temperature and pressure only affect volumetric flow measurement hence making volumetric controllers generate inaccurate results.
On the other hand, mass flow controllers cannot be affected by temperatures or pressure changes; hence, one is always sure of the accurate results. It is why many industries prefer mass flow controllers to volumetric flow controllers in their various applications.
In most cases where other flow controllers are employed, the results are inaccurate since the flow controllers contain flow control valves. The flow control valve has a built-in amount of hysteresis, which causes fluctuations in the temperature and pressure, thus leading to poor measurement results.
Mass flow controllers operate under a thermal mass flow where it measures a small size line of gas moving through a pipe from the primary gas flow system.
How Gas Mass Flow Controller Operates
A mass flow controller device for gas contains elements such as; electronics, flow sensor, and solenoid flow control valve, which acts as an actuator in most cases. The system operators will use electrics in the reference value setting through an analog signal.
The sensor generates the actual measurement value, and it compares it with the reference value in the controller device, thus adjusting the flow control valves as required. The thermal output of the mass flow sensor is directly proportional to the heated feature of gas in the measuring tube.
It makes it easier to calculate calibration, especially when some air, such as nitrogen gas, is calibrated. It is why gas mass flow controllers are known to be more flexible than other flow controllers.
Attributes and options for gas mass flow controllers
1. Accuracy
Mass flow controllers for gases are specified to have standard accuracy and linearity of + or – 0.5% F.S.
2. Flow Ranges
The flow range is between 0 to 50 cm and 0 to 10,000scccm. The customer requirements are also available in this model.
3. Displays
There are units with and without integrated displays. It would be best if you choose the best device for your application, depending on its type.
4. Power
The power range in mass gas flow controllers is 12 VDC or 24 VDC. There is also the availability of power adapters to work with the versions of 12 VDC.
5. Wetted Materials
Wetted materials such as stainless steel and aluminum are used to construct the path for the flowing gas and other device structure.
6. Signal Input and Output
All signal output and commands are 0 to 5 VDC. The models are having a D- suffix user-selectable feature of external or internal signal command options. The integrated potentiometers set the internal setpoint, while there is a 0 to 5 VDC supplement at the outer part.
7. Gases Calibration
There may be calibration of units for dry or clean gases. There is the availability of standard gas selection, as shown in the information order. To obtain non-standard gas calibration information, you should contact the factory or manufacturing industry.
8. Fluid Connection
As standards, all the units have tube fittings which are compression type, although the non-standard size and fittings are also available when you request them.
9. Multiple Gases
The factory registering the flow of different gases, usually three or more, can configure display models of 80D and 80 S.D. The system operators use the front panel switches to select the flowing gas. The flow controller then adjusts the output signal and the display automatically and as required.
Despite this feature, there are some gases which, when put together or mixed, the measurement may not be possible.
10. Electrical Connection
There is a pigtail lead that terminates the optional cable meter assembly and is made for wiring enhancement. All the units have a 92cm output cable of a 9-pin D connector, 15- pin D connector, or 6- pin P.S./ 2 connectors.
Conclusion
The industrial gas mass flow controller is an important device that performs various applications in industries. They provide the best accurate results and require low maintenance costs, making the best choice to measure gaseous substances.
