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Subject: Re: Calibration of Mass Flow Controllers

Date: 09/13/02 at 11:15 AM
Posted by: Donald Mattox
E-mail: donmattox@svc.org
Message Posted:

In Reply to: Re: Calibration of Mass Flow Controllers posted by Pat McMahon on 09/12/02 at 10:32 PM:

Pat: You are quite right there must be a pressure differential for there to be a flow - my error. I have never used a bubble flow meter (BFM) in low-vacuum situations. I think that they are primarily used at near-atmospheric, constant-temperature situations. However the concept is certainly valid. The test system could be set up two ways. one: the control valve (CV) - MKS/MFM - BFM and two: CV - BFM - MKS/MFM. In situation 1 the gas is heated somewhat in the MFM and might affect the BFM reading (make it read higher than at room temperature). In 2 the gas might contain vapor after passing though the BFM and thus give more cooling in the MFM making it read as if more gas was flowing.
Thanks for pointing out my error. Don Mattox

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