🚀 go-pugleaf

In article <7o0lgo$qga$1@bgtnsc03.worldnet.att.net>, 
benmiller@worldnet.att.net says...

>What flow rate range do you need to measure, and at what accuracy?

Ah - ha - thats a good question ~`:o

Anywhere from 0.1 to 20 Litres/min of equivalent atmospheric pressure, hence
proportional to that mass flow at the higher pressures I'm interested in.
I believe air mass (STP) is around 1.6g/m^3 therefore I'd be looking to
measure the flow of 0.16mg to 320mg per minute at STP. Since the pressure
can vary from 500psi to 5000psi then I'd be looking at minimum flow of
around 0.16mg x 500/14.7 to a (high) maximum of 320mg x 5000/14.7 per minute,
thats a dynamic range of about 5 decades ie 5 to about 100,000. Hence I'd be
looking to resolve to 16 bits best case and 12bits worst case (since I
will handle some scaling to bring down the dynamic range once I have settled
on the best pressure range). Absolute accuracy need only be 5% at this stage
to keep costs down but would like to achieve repeatability.

Once I've decided on the best range of operation, then I expect I will only
need to resolve to 12bits A to D and accuracy of about 2%.

Response time to change in flow should be less than 5mS if at all possible.

-- 
Rgds ~`:o)
Mike
Perth, Western Australia
Mailto: <erazmus@wantree.com.au>
99% efficient RAPS charger, GMH Turbo with Twin tyres, surplus parts etc
http://www.wantree.com.au/~erazmus
Some say there is no magic but, all things begin with thought then it becomes
academic, then some poor slob works out a practical way to implement all that
theory, this is called Engineering - for most people another form of magic.
" ...mmm thats because the laws of physics exceed the boundaries of the
contractual agreement (and the money ain't enough either)...  "