tmh Thanks for valuable and very good feedback. I'm talking about, lets say 50 ml of H2-gas over 15 minutes, and I think we can accept a back-pressure on about half a bar overpressure without problems. The linear displacement sensor sounds interesting, and I'm completely unfamiliar with anything like that. Do you have any further tips about them, who sells them etc.. I am following up the piston-lead via a couple of MFC companies. MP
"tmh" <> wrote in message news:[EMAIL PROTECTED] > Fair enough... I wasn't sure from your original post if you'd > considered issues such as pressure and mass flow vs volumetric flow > but it sounds like you have plenty of experience in this area. > > One thing that does occur to me though is that there's nothing to stop > you connecting two MFM's with different ranges in series. Then your > software can choose each time whether to take the reading from the > low-range MFM, or the high-range MFM if the low-range one is > saturated. I think MFM's have a pretty high tolerance to overrange and > I don't think a low-flow model will present much a bigger flow > restriction than a high-flow one, but you'd need to check this. > > If you decide the piston is the way to go, have you considered using > some kind of linear displacement transducer instead of image analysis? > What kind of volume do you need to measure over what time scale? Is > the process that evolves the hydrogen insensitive to pressure changes > or what is the maximum back pressure you can accept? There must be > lots of other possible ways to do it e.g. have the gas displace a > liquid into a container on a balance, mass spectrometry... ;-) > > You could ask a calibration lab or a company such as Chell > (http://www.chell.co.uk) about volume calibration equipment - or how > about the manufacturer of your MFC's? (as a customer of MKS UK in the > past I've found them very approachable when I had questions). > > Hope this helps, and hope that you also get some answers from IMAQ > experts as you originally asked for!
