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'[EE]: detect waterflow'
2001\05\08@123143 by Patrik Husfloen

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Are there any clever ways to detect waterflow in a hose/tube?


/Patrik

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2001\05\08@124417 by Mark Newland

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Microphone

Patrik Husfloen wrote:

> Are there any clever ways to detect waterflow in a hose/tube?
>
> /Patrik
>
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2001\05\08@125457 by Patrik Husfloen

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Didn't think of that, what kinf of a microphone goes well with water?

/patrik


----- Original Message ----- From: "Mark Newland" <spam_OUTapeTakeThisOuTspamESKIMO.COM>
To: <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
Sent: Tuesday, May 08, 2001 6:42 PM
Subject: Re: [EE]: detect waterflow


{Quote hidden}

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2001\05\08@125649 by Shawn Yates

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Fire alarm compananies detect when water flows through the sprinkler system
and set off an alarm.

If the tube starts empty, just an air gap switch that will be shorted when
covered with water would work, unless you are trying to detect FLOW not just
the presence of water.

How about a small impeller and and monitor the shaft for rotation.  Then you
could get realy fancy and measure the speed of the flow.



Just some thoughts.

Shawn

{Original Message removed}

2001\05\08@130948 by Patrik Husfloen

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Yes, the tube would be filled at all times and I would only want to monitor the actual flow.
Impeller is one way to go although I'm looking for something more simple :)

Thanks.

Patrik


----- Original Message ----- From: "Shawn Yates" <syatesspamKILLspamCARETECHNOLOGIES.COM>
To: <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Sent: Tuesday, May 08, 2001 6:49 PM
Subject: Re: [EE]: detect waterflow


{Quote hidden}

> {Original Message removed}

2001\05\08@130958 by James R. Cunningham

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Strap it on the OUTSIDE of the pipe.

Jim

Patrik Husfloen wrote:

> Didn't think of that,
> what kinf of a microphone goes well with water?
>
> /patrik
>
> {Original Message removed}

2001\05\08@132411 by Dal Wheeler

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A small thermister/heating element in line.  Temp should be proportainal to
flow.  Any particulate in the fluid?

You can get as cleaver as you have money.  Depending on your project
funding, you might look at installing some of those doppler flow meters; you
need faily large pipe diameters to make it work though.  (not to mention
$$$)


{Original Message removed}

2001\05\08@132554 by Roman Black

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Patrik Husfloen wrote:
>
> Yes, the tube would be filled at all times and I would only want to monitor the actual flow.
> Impeller is one way to go although I'm looking for something more simple :)


Hi Patrik, as an apprentice I did six months with
the instrument fitters in heavy industry, we made and
maintained all the high-tech (and low tech!) sensors
for the industrial processes.

One of my favorites was the "orifice" sensor, this
works well with liquids, gases, toxic sludge, etc,
we mainly used it to measure the propane fuel gases
feeding into big ovens.

Its very simple and has no moving parts, you place an
"orifice" in the pipe that has a hole of a set diameter.
Then a pressure sensor before and after the orifice
tell you what the flow rate is. The higher the flow rate
the more pressure difference between the two. Some light
viscosity liquids like water can cavitate at the orifice
so you place a filter just before the setup to smooth
the flow. You can buy complete sensor units like this
but they are easy to make. :o)
-Roman

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2001\05\08@145239 by Patrik Husfloen

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Doh! :)



----- Original Message ----- From: "James R. Cunningham" <EraseMEjrcceaspam_OUTspamTakeThisOuTBELLSOUTH.NET>
To: <PICLISTspamspam_OUTMITVMA.MIT.EDU>
Sent: Tuesday, May 08, 2001 8:26 PM
Subject: Re: [EE]: detect waterflow


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2001\05\08@145511 by Patrik Husfloen

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This sounds very interesting, I will have to look into it,
if you got any link etc, please post them :)

Thanks,

Patrik

{Original Message removed}

2001\05\08@150453 by Ethan Swint

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You can use a venturi tube, where it closes down the hose diameter a bit.  A
port in the narrow part of the tube will have a lower pressure than a port
on a larger width of the tube.  (increased fluid velocity -> lower fluid
pressure)  A simple differential pressure switch would be a transducer.

Ethan Swint
RemoveMEEthan_SwintTakeThisOuTspambaylor.edu

----- Original Message -----
From: "Patrik Husfloen" <spamBeGoneu58611234spamBeGonespamTELIA.COM>
To: <TakeThisOuTPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU>
Sent: Tuesday, May 08, 2001 12:04 PM
Subject: Re: [EE]: detect waterflow


> Yes, the tube would be filled at all times and I would only want to
monitor the actual flow.
> Impeller is one way to go although I'm looking for something more simple
:)
{Quote hidden}

system
> > and set off an alarm.
> >
> > If the tube starts empty, just an air gap switch that will be shorted
when
> > covered with water would work, unless you are trying to detect FLOW not
just
> > the presence of water.
> >
> > How about a small impeller and and monitor the shaft for rotation.  Then
you
> > could get realy fancy and measure the speed of the flow.
> >
> >
> >
> > Just some thoughts.
> >
> > Shawn
> >
> > {Original Message removed}

2001\05\08@180348 by Olin Lathrop

face picon face
> Are there any clever ways to detect waterflow in a hose/tube?

There are many commercial flow meters available that mostly work on having
the liquid drive a mechanical impeller.  I saw a flow meter in a research
lab once that worked on a magnetic principle.  The flow cut accross a
magnetic field, which induced a voltage in the orthagonal direction.  The
navy was funding the research.



********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, EraseMEolinspamembedinc.com, http://www.embedinc.com

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2001\05\08@182232 by Gennette, Bruce

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How about building a capacitor out of a fixed external plate and a pivoted
internal one. Flow lifts the internal plate, changing the capacitance.

Bye.

{Original Message removed}

2001\05\08@184413 by David VanHorn

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>
>Are there any clever ways to detect waterflow in a hose/tube?

Stand under the end :)

Ultrasonics works. You get doppler shift, as the water moves, carrying the
sound along faster or slower, depending on direction.
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2001\05\08@191637 by Patrik Husfloen

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> Ultrasonics works. You get doppler shift, as the water moves, carrying the
> sound along faster or slower, depending on direction.

sounds expensive/complicated :)
I've gotten a few good ideas though, I'll make sure to post it whenever it gets done. :)

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2001\05\08@224036 by Tom Messenger

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At 03:39 PM 5/8/01 -0400, you wrote:
>> Are there any clever ways to detect waterflow in a hose/tube?
>
>There are many commercial flow meters available that mostly work on having
>the liquid drive a mechanical impeller.  I saw a flow meter in a research
>lab once that worked on a magnetic principle.  The flow cut accross a
>magnetic field, which induced a voltage in the orthagonal direction.  The
>navy was funding the research.

Michael Faraday discovered this principle and attempted to use it to
measure the water velocity of the Thames river around 1834. Not having
amplifiers at his disposal to resolve microvolt signals, he was unable to
ascertain the answer.

But as Newton pointed out, we who stand on the shoulders of giants can see
a bit further... the electromagnetic water velocity meter is old hat now
days. In certain areas, it excels but in many common applications, it
suffers from contamination from the exposure of the measuring electrodes in
the fluid. (Capacitively coupled electrodes have been tried with some
success but this has other problems). This method suffers in clean water
applications from the high source impedance of the resulting generator.  In
"dirty" fluids, it does better but then suffers from contamination from
whatever is in the fluid. AC drive is a prerequisite by the way to avoid
plating/de-plating of the electrodes.

Doppler velocity meters will to the same job somewhat easier without the
problems of electrode fouling.

If all you want is flow/no flow type of indication, consider the thermal
methods or the impeller methods - cheap and work reasonably, if high
accuracy is not required.

Tom Messenger

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2001\05\09@020759 by Ray Gardiner

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It depends on what accuracy is required, I have developed a number of
commercial mag flow meters over the last 10 years. Some pic based.
If you just want flow/noflow indication AND you have power available
you can simplify things by going back in time to the old AC mag meters.
You can use an old fan motor (without the rotating bits) and apply mains
power, That gives plenty of flux, you will now see an ac millivolt level
signal on the electrodes mounted either side of the pipe. Amplify that
ac signal which will be linearly proportional to flow. Make some
provision for adjusting the zero offset. Accuracy won't be great (+-5%)
but easily good enough for flow/no flow indication.

{Quote hidden}

What are you applying the ac drive to exactly?. The electrodes?

One system we used applied bursts of high frequency to the electrodes
as a cleaning signal. Seemed to work pretty well. But you need to be
carefull that the cleaning signal doesn't upset the uvolt flow signals.

With high impedance analog ccts these days the electrode contamination
over time is not really the issue it once might have been.
Ray Gardiner RemoveMErayEraseMEspamEraseMEdsp.com.au
[ 2001 ]

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2001\05\09@021420 by Alexandre Domingos F. Souza

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>It depends on what accuracy is required, I have developed a number of
>commercial mag flow meters over the last 10 years. Some pic based.
>If you just want flow/noflow indication AND you have power available
>you can simplify things by going back in time to the old AC mag meters.
>You can use an old fan motor (without the rotating bits) and apply mains
>power, That gives plenty of flux, you will now see an ac millivolt level
>signal on the electrodes mounted either side of the pipe. Amplify that
>ac signal which will be linearly proportional to flow. Make some
>provision for adjusting the zero offset. Accuracy won't be great (+-5%)
>but easily good enough for flow/no flow indication.

       The problem is making this watertight! :o) I did it in a following manner: a self-contained fan, with an input and an output. in the border of one of the pads, a litte (yep, little) metal. So when it turned inside of the "cage", it would pass besite a hall effect sensor and trigger a frequency-to-voltage circuit (since the client wanted it in a d'arsonoval style). I use this kind of meter in every flow-meter application I do. It can ever be bidirecional - use the pads a bit turned to the side and 2 hall-effect sensors. One at each side. This gives you flowing and direction.

       Not fancy, but it works® :o)

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2001\05\09@022713 by William Jacobs

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Patrik,
       I use a flow switch to turn on an instant hot water heater.  I epoxied
a magnet in a 1/2 inch cpvc pipe about 3 inches long.  This just  slides
in a piece of 3/4 inch cpve pipe.  There is a 't' fitting and a reed
switch on the top.
       Let me draw a poor picture

               sw   switch
             xxxxx
             x   x
             x   x
             x   x
             x   x
             x   x
             x   x
             x   x









Patrik Husfloen wrote:
>
> Are there any clever ways to detect waterflow in a hose/tube?
>
> /Patrik
>
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2001\05\09@032127 by William Jacobs

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Patrik,
       Sorry about the previous unfinished picture.
       I use a flow switch to turn on an instant hot water heater.  I
epoxied
a magnet in a 1/2 inch cpvc pipe about 3 inches long.  This just  slides
in a piece of 3/4 inch cpvc pipe.  There is a 't' fitting and a reed
switch on the top.
       Let me draw a poor picture

               sw   reed switch
             xxxxxxx
             x     x
             x     x
          xxxx     x
   OUT             x
          xxxx     x
             x ama x   m is the magnet
             x a a x
             x a a x
             x aaa x
             x     x
             x   p x  p is a pin to keep the magnet
             x     x    from going out of the switch

                IN

Water comes in the IN, pushes the magnet up to the reed switch, opening
it,  and goes out the out.
Patrik Husfloen wrote:

bill


>
> Are there any clever ways to detect waterflow in a hose/tube?
>
> /Patrik
>
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2001\05\09@090810 by Olin Lathrop
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> But as Newton pointed out, we who stand on the shoulders of giants can see
> a bit further... the electromagnetic water velocity meter is old hat now
> days. In certain areas, it excels but in many common applications, it
> suffers from contamination from the exposure of the measuring electrodes
in
> the fluid. (Capacitively coupled electrodes have been tried with some
> success but this has other problems). This method suffers in clean water
> applications from the high source impedance of the resulting generator.
In
> "dirty" fluids, it does better but then suffers from contamination from
> whatever is in the fluid. AC drive is a prerequisite by the way to avoid
> plating/de-plating of the electrodes.

I only saw one in a research lab once, but I don't see why plating should be
more of a problem than with other metal immersed in the water.  After all
there is no (extremely little) current flowing thru the electrodes.  They
are used to measure induced voltage, not current.  That also helps overcome
high resistivity liquids to a point.  By the way, the one I saw was intended
to work in seawater.


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Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, RemoveMEolinspam_OUTspamKILLspamembedinc.com, http://www.embedinc.com

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2001\05\09@183148 by Peter L. Peres

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> what microphone

There are special mikes that vibrate in the water flow. Output amplitude
and frequency depend on flow. They are expensive unless someone did it
again using kynar.

Peter

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2001\05\10@142133 by Peter L. Peres

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a.c. MHD (crossfield) flow meters can use insulated electrodes. Like
painted or PTFE. == no corrosion problems + HEAVILY simplified readout
amplifier (no dc problems).

Peter

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2001\05\11@035318 by Mark Hull

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If you use an impeller design, it can be made as a sealed unit by having an impeller with metallic or magnetic blade tips, sensed from outside a non metallic tube using an inductive proximity detector.

---------------------------------------------------------------------
Mark Hull
Engineering / Technical
EMS (Africa) (Pty) Ltd
PO Box 1026, Melville, 2109, South Africa
Ph + 27 11 482 4470, Fax +27 11 726 2552

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2001\05\11@054219 by Roman Black

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Mark Hull wrote:
>
> If you use an impeller design, it can be made as a sealed unit by having
an impeller with metallic or magnetic blade tips, sensed from outside a
non metallic tube using an inductive proximity detector.


Actually I seem to remember Electronics Australia
magazine published a car computer kit, using
a standard sealed impeller sensor for fuel flow,
I think it was a Toyota sensor. :o)
-Roman

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