tmh Have used hundreds of MFCs from Brooks and Bronkhurst (Porter) in my LabVIEW applications, so I'm aware of their functionality.
On this potential new application, it could be that they are not good enough because the amount of gas could be to small over the time range in question, so I have to look at other alternatives. Also, they have a to static measuring range, meaning that I could easily get 100 % flow back if I for some seconds get to high gas flow, loosing information about the real volume totally. What I'm asking about is actually the equipment that these MFC companies use to calibrate their MFCs and MFMs, the volumetric glass cylinders with pistons etc, to collect gas. Martin "tmh" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > This sounds like an ideal application for a thermal mass flow meter > (MFM). These devices measure the flow of a gas between their inlet and > outlet using a thermal conductivity measurement. Typically the output > is given as a volumetric flow rate (e.g. cm^3 per minute) at standard > temperature and pressure, but what is actually being measured is the > rate of mass flow (i.e. number of grams or moles of gas per unit > time). If you integrate this with respect to time you will get the > total volume at stp which corresponds to the amount or mass. > > The meter will need to be calibrated for the gas in use, so you will > need to be sure either that your gas is (almost) pure H2, and buy a > MFM calibrated for H2, or that its composition is relatively constant > so that you can generate an appropriate calibration, else you will get > inaccurate results. > > MFM's and their close relatives, mass flow controllers (MFC's) are > available from many manufacturers but I've had very good experiences > with those from MKS. They are available with a serial interface and > the command protocol is easy to implement in Labview. I think the > digital version can even do the flow integration for you. They're not > cheap (maybe $1000?) but it sounds like this would probably be a > reliable and accurate solution to your problem. > > Hope this helps, please reply with any further questions...
