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Method for measuring very low flow rates of a gas? (Maybe a "passive peristaltic pump"?)

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BingoBaggins

Student
Nov 15, 2020
1
Hi all.

I'm trying to come up with a way to measure the very low flow rate of a gas (on the order of ml / day) without allowing backflow. Assuming this gas is under sufficient pressure to drive a metering mechanism, what would that mechanism be? As far as I've gotten: Is it possible to drive a peristaltic pump in reverse this way and count its revolutions? My intuition says no - the rotor would stall when a wheel began to engage the tube.
 
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Are you looking for a lab method or something that needs less attention?

In a lab, you might get away with passing the gas through a length of clear tubing, introducing a drop of oil into the stream once every couple of hours and measuring the distance between the drops in the tube.

A.
 
Does it need to be calibrated? It would seem to me that such low flows must be essentially in a vacuum, and an ionization gauge can measure down to 10^-11 Torr, which is ~10^-14 atm.

TTFN (ta ta for now)
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