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Subject: Re: Calibration of Mass Flow Controllers

Date: 12/16/02 at 11:16 AM
Posted by: Harvey Padden
E-mail: padh@biosint.com
Message Posted:

In Reply to: Calibration of Mass Flow Controllers posted by Allan Knoll on 09/12/02 at 8:12 AM:

The problem appears to be that you are calibrating an MFC, which reads sccm, with an burette, which reads ccm. The MFC is standardized, usually to 0C, while you are reading flow at something like 22C. You need to know your lab temperature and atmospheric pressure. Then you take the burette flow and multiply by T/(T+273.15) and then by P/760, where T is degrees C and P is mm mercury. If you are using dry air or nitrogen, you will also need to subtract about 3% from the flow to account for the vapor pressure of water in the burette.

BTW, we make calibrators that read directly in sccm. If you do many of these calibrations, they might be of interest. See www.biosint.com.

Harvey Padden

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