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Mike

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

Ben Miller

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Visit our Web site at http://home.att.net/~benmiller

B. Miller Engineering
1356 S. Sixth Ave
Des Plaines, IL  60018
Phone 847-390-0596
Fax  847-390-0599
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Mike <erazmus@wantree.com.au> wrote in message
news:7numbj$hol$1@centipede.wantree.com.au...
> Hi chaps,
>
> Looking for an Air Flow Meter - preferrable hot wire type which can handle
> an operating pressure of 2500psi up to about 5000psi. The actual pressure
is
> likely to vary from 500psi and could be anywhere up to 500psi maximum.
>
> Needless to say the micro I am developing will read the pressure but I'm
> having trouble getting a hot wire AFM which can handle this pressure, it
> would be great to find one with electronics to give a log or linear output
> but I suppose I could do my own bridge if need be...
>
> --
> Rgds ~`:o)
>
> Mike
> Perth, Western Australia             Mailto: <erazmus@wantree.com.au>
> 99% efficient RAPS charger, GMH Turbo car 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)...  "
>

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)...  "

On 1 Aug 1999 05:50:50 GMT, erazmus@wantree.com.au (Mike) wrote:

>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

That's some mean turbo there Mike ;-)

Peter
PERTH - WESTERN AUSTRALIA
Remove the NOWHERE from reply address

Off hand I don't know of anything that will handle that range. I was
starting to think about measuring the differential pressure across an
orifice since pressure transducers could handle that pressure requirement,
but the DP would go as the square of that flow rate, which would be an even
worse dynamic range. Have you asked any of the transducer manufacturers?

Ben Miller

--
---------------------------------------------------------------------
Visit our Web site at http://home.att.net/~benmiller

B. Miller Engineering
1356 S. Sixth Ave
Des Plaines, IL  60018
Phone 847-390-0596
Fax  847-390-0599
--------------------------------------------------------------------

FCI has some that will do it, but don't expect to get one cheap. Last time
we got one, it was in the $1500 range. http://www.fluidcomponents.com/

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Electricity from the sun since 1979
www.windsun.com
www.solar-electric.com (online store)
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Mike <erazmus@wantree.com.au> wrote in message
news:7o0n7q$fm2$1@centipede.wantree.com.au...
> In article <7o0lgo$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)...  "
>

In article <7o20ca$hbl$1@bgtnsc01.worldnet.att.net>, 
benmiller@worldnet.att.net says...
>
>Off hand I don't know of anything that will handle that range. I was
>starting to think about measuring the differential pressure across an
>orifice since pressure transducers could handle that pressure requirement,
>but the DP would go as the square of that flow rate, which would be an even
>worse dynamic range. Have you asked any of the transducer manufacturers?

I had a brief scrounge through some catalogs in Oz, but nothing came up,
hence my query to the news groups...

-- 
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)...  "

In article <7o2cc0$fag$1@bgtnsc02.worldnet.att.net>, wlauzon@worldnet.att.net 
says...
>
>FCI has some that will do it, but don't expect to get one cheap. Last time
>we got one, it was in the $1500 range. http://www.fluidcomponents.com/

mmm OK - will have a look thanks - I'll only need one for a reference and
then keep it as an instrument once I decide how to make a small one with
less dynamic range as is required etc...


-- 
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)...  "

On 2 Aug 1999 07:10:17 GMT, erazmus@wantree.com.au (Mike) wrote:

>In article <7o2cc0$fag$1@bgtnsc02.worldnet.att.net>, wlauzon@worldnet.att.net 
>says...
>>
>>FCI has some that will do it, but don't expect to get one cheap. Last time
>>we got one, it was in the $1500 range. http://www.fluidcomponents.com/
>
>mmm OK - will have a look thanks - I'll only need one for a reference and
>then keep it as an instrument once I decide how to make a small one with
>less dynamic range as is required etc...

I don't know much (anything) about hot wire technology, but use
turbine technology for hydraulics; the turbine meters are more
reasonable than that and can handle the pressure, I'm sure, and range,
I believe.  They specifically DO handle gasses.

You might call Sponsler, a local manufacturer from I purchase mine, at
864-647-2065.

George