Mass Flow Controller Structure and Operation<\/h3>\n\n\n\n
The main components of a typical thermal mass flow controller are a flow sensor, control valve, and bypass. Operation is automatic and consists of the following steps.<\/p>\n\n\n\n
![\"\"](\"https:\/\/lintec-mfc.co.jp\/en\/wp-content\/uploads\/2024\/03\/Mass-Flow-Controller-structure.png\")
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- Mass sensor is heated to measure fluid movement (mass flow rate)<\/li>\n\n\n\n
- A bridge circuit converts the mass flow rate into an electrical signal<\/li>\n\n\n\n
- The mass flow signal is converted to an electrical signal and amplified with an operational amplifier<\/li>\n\n\n\n
- The signal is digitalized with an AD\/DA converter<\/li>\n\n\n\n
- The set flow rate is compared with the current flow rate in an arithmetic circuit<\/li>\n\n\n\n
- PID control is used to drive the valve actuator<\/li>\n\n\n\n
- Steps 1 to 6 are repeated (feedback control)<\/li>\n<\/ol>\n<\/div>\n<\/div>\n\n\n\n
Principle of Mass Flow Controller Measurement<\/h3>\n\n\n\n
The flow sensor principle of the thermal mass flow controller is as follows<\/p>\n\n\n\n
![\"Mass](\"https:\/\/lintec-mfc.co.jp\/en\/wp-content\/uploads\/2023\/07\/\u30de\u30b9\u30d5\u30ed\u30fc\u30bb\u30f3\u30b5\u539f\u7406.png\")
Mass Flow Sensor Principle<\/figcaption><\/figure>\n\n\n\n - \n
- Two electric heating wires are wound around a stainless steel capillary tube, which is heated to the same temperature. These electric heating wires are placed on the path through which the fluid flows.<\/li>\n\n\n\n
- When the gas is shut off, the upstream and downstream electric heating wires maintain the same temperature and are not out of balance.<\/li>\n\n\n\n
- However, as the gas flows, the upstream electric heating wire loses heat from the gas and flows downstream, changing the balance.<\/li>\n\n\n\n
- To detect this change, a bridge circuit installed in the capillary tube is used. The bridge circuit is used to measure electrical signals and compare the signals from the upstream and downstream electric heating wires.<\/li>\n\n\n\n
- The change in balance due to gas flow is converted into an electrical signal by a bridge circuit. This signal is measured as a mass flow rate.<\/li>\n<\/ol>\n\n\n\n
Thermal mass flow controllers use this heat-based measurement principle to measure flow rates. This measured flow rate information is then fed back to the subsequent control circuitry, which performs control actions to bring the valve closer to the set flow rate by controlling the valve. Mass flow controllers from different companies may have different features depending on the flow sensor design and patented technology.<\/p>\n\n\n\n
Lintec Mass Flow Controller Features<\/h2>\n\n\n\n
Lintec\u2019s mass flow measurements are based on a unique low-temperature sensor structure; we started with the gas MFC production and were one of the first companies in the world to develop MFC for liquid applications.<\/p>\n\n\n\n
![\"Lintec's](\"https:\/\/lintec-mfc.co.jp\/en\/wp-content\/uploads\/2023\/08\/Mass-Flow-Ambient-Temperature-Sensor-Description.png\")
Low temperature sensing structure<\/figcaption><\/figure>\n\n\n\n Lintec’s mass flow controllers employ a low-temperature sensing structure (ambient temperature compensated sensor) to enable high precision and high speed measurement. Our sensors have an original structure that prevents the sensor\u2019s temperature from rising above the necessary level by having the ambient temperature feedback sent to the sensor.<\/p>\n\n\n\n
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- Less thermal damage to the sensor (longer life): <\/strong>The low-temperature sensing structure keeps the temperature of the flow sensor low. This results in less thermal damage to the sensor and longer product life cycle.<\/li>\n\n\n\n
- Low risk of thermal decomposition of fluids (e.g. ozone can be controlled):<\/strong> Since the measurement is taken at lower temperatures than typical mass flow controllers, it is ideal for flow control of gases with a high risk of thermal decomposition, such as ozone. The thermal effect on fluids is minimized.<\/li>\n\n\n\n
- High Speed flow control capability: <\/strong>The low-temperature sensor structure enables a response time that is overwhelmingly faster than that of conventional thermal sensors. Excellent performance when high-speed flow control is required.<\/li>\n<\/ol>\n\n\n\n
This low-temperature sensor structure enables highly accurate and fast flow measurement and control.<\/p>\n\n\n\n
Gas and liquid gas mass flow controller<\/h3>\n\n\n\n
Gas mass flow controllers are abbreviated as \u201cMFC\u201d; these fluid control devices were developed for precise gas control, predating the introduction of the liquid mass flow controllers. Gas volume tends to change under the influence of temperature and pressure according to the combined gas law, but the MFC measurement is unaffected by these factors, which enables it to automatically control flow rate to a set point with a built-in control valve. Thermal MFCs that utilize the principle of specific heat at constant pressure are the main type of mass flow controllers.<\/p>\n\n\n\n
Click here for product page<\/a><\/p>\n\n\n\n
Liquid mass flow controllers are abbreviated as \u201cLFC\u201d and were developed for precise liquid flow control. Lintec was the first company in the world to develop a thermal liquid mass flow controller and thus contribute to technological innovation in semiconductor industry. In addition to the thermal type, there are also Coriolis and differential pressure LFCs.<\/p>\n\n\n\n
Click here for product page<\/a><\/p>\n\n\n\n
Summary:<\/h4>\n\n\n\n
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- Gas gas mass flow controllers are fluid control devices dedicated to gases, enabling precise flow control without being affected by temperature or pressure.<\/li>\n\n\n\n
- Liquid mass flow controllers, abbreviated as \u201cLFC\u201d, provide precise liquid flow control. Lintec was the first company in the world to develop a thermal liquid mass flow controller.<\/li>\n<\/ul>\n\n\n\n
MFC – FAQ<\/h2><\/div><\/div>\n\n\n\n
\n\n<\/div>\nWhat is the difference between mass flow and volumetric flow?<\/h3><\/div><\/div>\n\n\n\n
Mass flow indicates weight per hour, g\/min for liquids. Volumetric flow rate indicates volume, in m\u2113\/min.<\/p>\n<\/div><\/a>
<\/div><\/div>\n<\/div>\n\n\n\n\n<\/div>\nWhat does mass flow mean?<\/h3><\/div><\/div>\n\n\n\n
In addition to the meaning of mass flow, it is generally used as an abbreviation for mass flow controller (flow control device).<\/p>\n<\/div><\/a>
<\/div><\/div>\n<\/div>\n\n\n\n\n\nWhat is the difference between a mass flow meter and a controller?<\/h3><\/div><\/div>\n\n\n\n
Both mass flow controllers and mass flow meters measure flow rates, but mass flow controllers control the flow rate so that the measured flow rate matches the set value.<\/p>\n<\/div><\/a><\/div>\n<\/div>\n\n\n\n
\n<\/div>\nWhat is the mass flow controller used for?<\/h3><\/div><\/div>\n\n\n\n
Mass flow controllers are used for high-precision flow control in semiconductor manufacturing processes and other deposition processes, analyzers, etc.<\/p>\n<\/div><\/a>
<\/div><\/div>\n<\/div>\n<\/div>\n\n\n\n\n\n<\/div>\nWhat is the role of the mass flow meter?<\/h3><\/div><\/div>\n\n\n\n
A mass flow meter is an instrument for mass flow measurement. Unlike mass flow controllers, mass flow meters cannot control the flow rate by themselves.<\/p>\n<\/div><\/a>
<\/div><\/div>\n<\/div>\n\n\n\n\n<\/div>\nWhat is operating differential pressure?<\/h3><\/div><\/div>\n\n\n\n
Operating differential pressure is the differential pressure between primary and secondary pressure required for normal operation of a mass flow controller or mass flow meter and is generally 50 to 300 kPa.<\/p>\n<\/div><\/a>
<\/div><\/div>\n<\/div>\n\n\n\n\n<\/div>\nWhat is the control range of the mass flow controller?<\/h3><\/div><\/div>\n\n\n\n
Typically, the control range of a mass flow controller is 2% to 100% full scale. Depending on the model and options, control below 2% F.S. is also possible.<\/p>\n<\/div><\/a>
<\/div><\/div>\n<\/div>\n\n\n\n\n<\/div>\nWhat is the operating differential pressure of the mass flow controller?<\/h2><\/div><\/div>\n\n\n\n
Typical mass flow controllers have an operating differential pressure of 50 to 300 kPa. Low differential pressure mass flow controllers are required for flow control of liquefied gases with low primary pressure.<\/p>\n<\/div><\/a>
<\/div><\/div>\n<\/div>\n<\/div>\n\n\n\n\n\n<\/div>\nHow do I use the mass flow controller?<\/h3><\/div><\/div>\n\n\n\n
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- 1.Connect MFC to the piping<\/li>\n\n\n\n
- Conduct a leak check<\/li>\n\n\n\n
- Power the MFC<\/li>\n\n\n\n
- Conduct a zero point check<\/li>\n\n\n\n
- Apply the required pressure<\/li>\n\n\n\n
- Input the set point<\/li>\n<\/ol>\n<\/div><\/a><\/div><\/div>\n<\/div>\n\n\n\n\n<\/div>\n
What is the conversion factor?<\/h3><\/div><\/div>\n\n\n\n
Mass flow controllers use the specific heat of a gas to measure and control its mass, conversion factor is a coefficient individual to each gas type; N2 is taken as a standard value with it\u2019s conversion factor equaling \u201c1\u201d.<\/p>\n<\/div><\/a>
<\/div><\/div>\n<\/div>\n\n\n\n\n<\/div>\nWhat is the principle of mass flow measurement?<\/h3><\/div><\/div>\n\n\n\n
Mass flow rate is measured based on the principle that a heat-generating resistor upstream and downstream of the mass flow sensor generates heat to reach a certain temperature, and the heat of the resistor is taken away (specific heat) in proportion to the mass passing through the sensor.<\/p>\n<\/div><\/a>
<\/div><\/div>\n<\/div>\n\n\n\n\n<\/div>\nWhat mass flow measurement methods are available?<\/h2><\/div><\/div>\n\n\n\n
Thermal mass flow controllers were the first ones to be introduced to the semiconductor industry, and remain to be the most commonly used type of MFCs. There are also Coriolis type and differential pressure type MFCs that do not require conversion factor application.<\/p>\n<\/div><\/a>
<\/div><\/div>\n<\/div>\n<\/div>\n\n\n\n\n\n<\/div>\nWhat mass flow fittings are available?<\/h3><\/div><\/div>\n\n\n\n
Swagelok tube fittings and VCR type fittings are the most common ones. The piping size is usually written in inches with \u00bc being the most common one; there are also \u00bd, 3\/8, 1\/8 and 1\/16 sizes, which are applied depending on the fluid type and the flow rate.<\/p>\n<\/div><\/a>
- Low risk of thermal decomposition of fluids (e.g. ozone can be controlled):<\/strong> Since the measurement is taken at lower temperatures than typical mass flow controllers, it is ideal for flow control of gases with a high risk of thermal decomposition, such as ozone. The thermal effect on fluids is minimized.<\/li>\n\n\n\n
- Less thermal damage to the sensor (longer life): <\/strong>The low-temperature sensing structure keeps the temperature of the flow sensor low. This results in less thermal damage to the sensor and longer product life cycle.<\/li>\n\n\n\n