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

[BingoBaggins]

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.

 

[zeusfaber]

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.

 

[IRstuff]

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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[itsmoked]

Classic Mass Flow Sensor.

Keith Cress
kcress -

http://www.flaminsystems.com