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   Cv calculator: Multiply sccm @20 psig by 2.0 10-5 |
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Stock Precision Orifices The table below lists 70 stock orifices organized by flow of N2 at 20 psig. If you know the required diameter in number of .001", these are N, R & F IDs. For a different N2 pressure and/or a different gas use the calculator table. |
Universal Microsystems 48531 Warm Springs Blvd. Bld. 415 Fremont, California 94539 Phone: 510-490-3900 Fax: 510-490-3916 |
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Cv calculator: Multiply sccm @20 psig by 2.0 10-5 |
 Dimensional specificationsAll diameters are within 2 micron of specification dimension |
Orifices designated with R or N are made from synthetic single crystal sapphire (Ruby without the Chromium dopant) There are two configurations. When the inlet side has a cone shape, the ID is N. When the inlet side is a flat shape the ID is R. Even though the channel diameters are identical the flow varies as indicated in the table. Orifices identified with S or T are made from single crystal silicon whose dimensions are made with photolithography. |
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Limit catastrophic gas flow Choose a Precision Orifice ID with flow rating Qs = 2-3X the maximum regulated flow. Flow ratings can be found from the table above or the calculator. See Detailed Information |
Backfill a Chamber in a Precise Time Assuming there is no loss of gas from the chamber during backfill, the time to fill to atmospheric pressure is given simply by: Time = V / Qs where V is the volume of the chamber. See Detailed Information |