Need ideas for liquid flow meter

    --Try the Omega catalog; might find something there. Their specialty
is about every kind of measurement device there is. Last time I looked they
had *4* catalogs..

--
        "Steamboat Ed" Haas         :  Never thought I'd live to see
        Hacking the Trailing Edge!  :  our "iron curtain" crumble...
                          www.nmpproducts.com
                   ---Decks a-wash in a sea of words---

If you're measuring flow rate, look for a venturi flow meter or the
like.  If you're measuring a fixed volume, a simple float on a toggle
switch has proven effective (open the back of your toilet).  A digital
scale is also good.

- Daniel

And if you want to control the volume (measuring it was just a way to tell
when to shut it off) then there are pumps which will deliver a set amount
per revolution, just count the revs.  They come in all sizes for all
volumes-per-second...

     We need more information.  What kind of fluid volume are you talking
about?  Do you want to meter a few drops of liquid into a test tube as
part of an analytical chemistry system, or measure water usage in an
irrigation pipeline on your farm?  How much accuracy do you need?
Is 10% good enough?  Is the fluid conductive?  Viscous?  Flammable?
Does it matter if the unit reads zero at very low flow rates?

     Try again, please.

                John Nagle

The idea is to measure a fixed volume of *WATER* provided from a hose,
to a receptacle within a vehicle,
which arrives at the "filling station" for replenishment several times
per working day.  Currently the process
is done manually, and requires a human to stand and watch the process
for 10-15 minutes, and we'd like to free
up the person for other tasks while the resevoir fills itself.
Basically, it would pay back very quickly in terms of
opportunity costs ...

Ideally, the amount would be user programmable, the device would fit
on a standard 1" hose, and the controller
would allow the delivery of a measured amount of water.  I'm aware
that a timer could come close, but there are
many variables which would have to be taken into consideration
(pressure, flow rates, time of day vs demand upon
the city mains), which could be alleviated by simply measuring the
volume through the device, and triggering a
solenoid to shut off the flow.

The pump idea is cool, but does not apply in the case of delivery from
a hose.  Just looking for the ability to shove the
hose in the spout, hit the start button, and walk away knowing that we
won't be pumping spillage down the drain if
the attendant fails to check back ...

<snip>

If the goal is to add a fixed amount of water each time, then you
might do better with a tank, a float switch (adjusted to switch when
the tank holds the desired amount), and a couple solenoid valves (or a
single three-way valve).  This might be easier than measuring/
integrating flow rate.  If the amount to add varies (e.g. for
different vehicles), or is a huge volume, then this suggestion is
likely off-target.  If the volume is small enough, elevating the tank
would eliminate the need for a pump -- though pumps aren't too
expensive.

HTH,

-- Larry

Thanks, Larry, but the holding tank idea was discarded fairly early on
in the process.

The idea is to use a minimally invasive approach to filling a fixed
size, albeit movable tank
using a hose.  Adding a holding tank with float valve etc. etc. uses
up too much space budget,
as the tank would have to be fairly large.  In addition, the capacity
of the system would be
limited by the holding tank size, whereas a flow based measurement
system could be used
to batch fill a bucket or a swimming pool, provided that the accuracy
is sufficient.

I was hoping that someone was aware of something like a turbine flow
meter with a digital output
which would say, fire every n units, or every rotation, provided that
a fixed volume was passed
with each rotation ... then the problem is reduced to capturing the
signal, and a simple firmware
problem ...

    You're working way too hard at this.  Just buy a standard
gas pump nozzle with automatic shutoff and hook it to the water hose.
They're about $50 to $100.

http://www.jmesales.com/department/2019/1/Nozzles.aspx

                John Nagle

Just as a side note.  How do they work.  Surely they cant have power
running though them. I would have thought there would be to much risk of
a spark.  I thought may be pressure build up in the nozzle when the end
is submerged. Any ideas.

Not very robotic I know, but just a mechanical problem thats been solved
and I can't figure out how.....


Thanks
    Rob

John Nagle wrote:

http://auto.howstuffworks.com/question25.htm

- Daniel

A simple and elegant approach.  This might just work, provided the
venturi vent and nozzle can be extended
into the resevoir ... apparently an experiment is in order 8-)