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COMPASS for Flow Overview (MFC calibration example)

Overview of what COMPASS for Flow is, what it can do, and how to set it up. Uses an example of calibrating a mass flow controller (MFC) and using that MFC to control the flow rates in the test.

See the below attachments. One is an example setup of a 200 scccm H2 MFC run in nitrogen.

The data file (.dat) and report (.doc) are for a 50 sccm H2 MFC run in nitrogen. 

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Comments

  • Avatar
    Steve Nelson

    The article references an attachment that appears to have been removed.

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    Kyle Clark

    Sorry, just added an attachment back in

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    Donald Tessmer

    How significant is the Reynolds number? What is the range?

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    Kyle Clark

    Hi Don - From the molbox1+ manual,

    "3.1.3.1 molbloc-L Operation
    In molbloc-L operation, the Ready/Not Ready indication also helps guard against using molblocs above their valid range by monitoring the Reynolds number of the flow. If the Reynolds number of the current flow exceeds 1300, the Ready () indicator flashes. The current Reynolds number value can be viewed using [P&T] (see Section 3.4.5). If molblocs are used within the pressure and flow range limits for the flowing gas and the pressure dependent calibration type (see Section 1.2.5), a Reynolds number of 1200 will never be exceeded (1300 is used as the warning limit to allow for individual molbloc differences)."

    Since the manual was published, the Reynolds number limit for a 3E4-L laminar molbloc with high pressure calibration has been increased to 1550 to allow for operation to 50 slm. Two 3E4-L molbloc elements can be used in parallel to achieve a nominal flow rate of 100 slm. Above 100 slm we offer sonic molbloc elements (critical flow venturi nozzle).

    With our sonic molbloc elements, Reynolds number is related to Back Pressure Ratio. From the manual, "molbox1+ continually calculates
    Re during flow measurement and can monitor the BPR to ensure that it does not exceed the choking ratio at the current Re conditions."

    More details in the molbox1+ manual that is available here, https://bit.ly/3clxhlL

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