Providing expertise on Mass Flow measurement working standard
The leading manufacturer of Semiconductor MFC equipment in Japan develops “mass flow measurement working standard” systems using pressure-based flow measurement technology, a well-established technology used in their premium quality MFC product.
The manufacturer leverages the working standard as mass flow reference to calibrate their MFCs in production and provides their customers the pressure based working standard for field maintenance purpose.
Figure 1 depicts the measurement traceability standards pyramid that is recognized worldwide by national metrology institutes as a standard framework for products which rely on accurate measurement data. The customer’s focus was establishing and adhering to a predefined working standard for the semiconductor manufacturers desired technical requirements. Reliability and accuracy of this data was crucial to achieve product quality driving the customers need for a unique pressure measurement solution.
The mass flow controller requires accurate measurement of differential pressure using two absolute pressure sensors. That’s quite some challenge, it’s like making sculpture using an engraving blade.
To maintain accuracy and reliability, the pressure sensor in the machine must guarantee high resolution over a wide range of pressure changes and exceptional stability over a wide period of time.
The solution The customer selected Druck’s TERPS sensor as their preferred choice for the cutting edge abilities of the technology delivering:
• TERPS’ resonant pressure sensing technology is a unique development by Druck’s engineers and provides stability 10 times better than piezo resistive sensor, with a resolution better than 10 ppm.
• TERPS helps the customer to accurately measure gas mass flow Q by measuring inlet pressure P1 and outlet pressure P2 located between the restrictor.
The higher is the mass flow, the higher is the pressure difference. Mass flow Q can be calculated using the following equation:
Q = kT (P12 – P22)
kT is restrictor dependent constant at temperature T.
TERPS offers digital output in ASCII format via RS-485 or RS-232 serial communication. In addition to these two serial communication interfaces, TERPS also provides USB interface for ease of connection and transfer of sensor data to a host computer.
By selecting the USB connection option, the user can power the TERPS sensor simply using a 5V USB bus power eliminating the need for any specialty power supply in their system.
Druck’s technology adds value The introduction of Druck’s TERPS provided the following benefits:
• High accuracy: the high quality and robustly designed digital pressure sensor provides best in class long term stability.
• Ease of use of user interface: simplify customer’s system. As a result, the customer could shorten development period to evaluate the sensors and complete the design of the system.
• Flexibility: Plenty of choices of pressure connections give customer flexibility to select fitting that matches their application.
• Worldwide technical expertise: Druck’s global network of highly qualified professionals ensures that local technical expertise can be provided anywhere in the world and with additional language support.
