In Reply to: Re: Calibration of Mass Flow Controllers posted by Donald Mattox on 09/13/02 at 4:28 PM:
First, thank you for your much appreciated input on the matter. Next, the set up is such that the bubble meter is attached to the output side of the MFC, so its as described by situation #1.
The output of the MFC is connected to the input of the bubblemeter which is open to atmosphere.
There is no opportunity for moisture pickup before measurement.
Gas flows through the MFC supplied at 20 psi from the bottle, so during the test the pressure drop is 20 psi. MFC "operational differential pressure" per the manual is 10 to 40 psid. I should be okay here. Under real usage, the MFC is of coarse connected to a chamber under vacuum, so the pressure drop is essentially 17 psi greater, but still within the range specified.
I must still test with different pressure drops to see what real effect there is, if any.