IMAQ application; measuring gas volume

[Plassen Martin]

I'm looking at a possible application where I have to
measure the volume of H2-gas by IMAQ, by looking at
a Mercury-column, or by looking at a piston in a transparent 
column.
Has anybody out there ever tried something like this, to
give me some tips ? Maybe also about possible vendors 
that makes volumetric measurment eqiupment suitable for this
purpose ?
Martin