Water movement detection

jmspaggi

Hi,

I'm looking for a solution to detect water movement on a pipe. If possible, without doing any hole because I would like to avoid leaking. Pipe can be copper or plastique (PEX).

The goal is to monitor water temperature, but only when watter is used, because when water is not moving, pipe temperature is going close to room temperature and this information is useless for me. I have one thermal sensor before the solar tank, one after, and one after the instant heater.

I can't use the instant heater relay to do so because in summer water is hot enought so it's not running.

Any idea/clue?

Thanks,

JM

Timothy D. Swieter

Is there some sort of float or fluid level device in the tank you mentioned? Maybe you could tape in that to see if the water is leaving the tank.

Another idea would be to attach some sort of microphone to the pipe. Maybe there is a different sound signature on the pipe when the water is flowing versus not flowing.

At what time do you need to detect the water is flowing? For instance if you know the water is always hotter when it is flowing maybe you can detect the movement by a temperature sensor on the pipe. If you are trying to turn on/off a heater based on the water flowing, then maybe this isn't the best solution because of the lag in the system.

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Timothy D. Swieter, E.I.
www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, uOLED-IOC, eProto for SunSPOT, BitScope
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Beau Schwabe

jmspaggi,

I would consider using a Pitot flow meter or a Calorimetric Flowmeter for this application.
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Edit:
Another option is to use ultrasonic flow detection.· Any kind of turbulence from joints, tube narrowing/widening, etc. will create an ultrasonic sound that can be·detected.· Sometimes the sound is even audible as a very high pitch hiss or squeal.· From what I understand it doesn't take much flow to generate adequate ultrasonic vibrations.
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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 11/25/2008 8:20:06 AM GMT

jmspaggi

Thats for your replies.

My first idea was to monitor the temperature. When it's going up, water is moving, when it's going down, water is not moving any more. The probleme with that is when Solar Water Tank will not be able to store enought energy. Then water temperature at the exit will slowing move down, like when water is not moving, even is we are using it.

I can also maybe monitor the water entry, because it should be below to room temperature. So when it's moving down water is moving, and when it's moving up, whater is not moving. But it summer, when water entry is "warm" (12C), it will take time detect the change.

But I'm not really sure of the accuracy of alll those "adjustments". For now, that's what I will use since I'm not able to find the right sensor.

I looked for Pitot flow at many different web sites to find a sensor (like http://www.omega.com/ppt/pptsc.asp?ref=PX209_PX219 ) but was not able to find anything under $200. Which is way to more regarding what I want to do. I' ready to pay $50, maybe $100, but not $200. Forget that.

The sound detection also can be a good idea. If I couple it with the temperature, maybe I can detect some mouvements base and the diferents values received from the sensors.

So in order to do the ultrasonic detection, what kind of sensor should I use?

Do you think I can use that: http://www.parallax.com/Store/Sensors/PressureFlexRPM/tabid/177/CategoryID/52/List/0/Level/a/ProductID/89/Default.aspx?SortField=ProductName,ProductName

Will the vibration be "big" enought to be detected?

Thanks,

JM

Beau Schwabe

jmspaggi,

The "Piezo Film Vibra Tab Mass" sensor that you pointed to will not have enough response at ultrasonic frequencies. You need an ultrasonic transducer designed for the purpose. There are some for gas, and there are some for fluid... the idea in principle is the same, however the typical ultrasonic frequency range is different between the two. A popular 40kHz ultrasonic transducer may or may not work, I don't know for sure.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

jmspaggi

Hi Beau,

Thanks for your reply. I searched for an ultrasonis sensor but it's still pretty expensive [noparse]:([/noparse] So I think I will first try to find a way to determine that water is moving based on the values I will get from the 3 sensor.

Another idea will be to do a loop or a curve with flexible pipe, and glue a FlexiForce Sensor on it. When the water will move, the pressure will change so will also the curve, and maybe I can detect that. The issue is I'm not sure it's going to move enought to be detected.

So I will still try to search a cheap solution which works [noparse];)[/noparse]

Thanks,

JM

Bruce Bates

JM -

It now becomes more obvious that this is a NEW installation. Although you said "If possible, without doing any hole because I would like to avoid leaking. Pipe can be copper or plastique (PEX)." Holes, properly installed, may be your least expensive solution.

If you use rigid pipe, you are going to have quite a few couplings, presuming this is a decent length run of pipe. You stand to have just as many leaks in those coupling joints as you would if you properly drilled and carefully tapped the pipe. If PEX is anything like PVC pipe, they even have PVC "dope compound" to seal any metal fitting which would be placed in a tapped hole. At that juncture the world is your own - you're inside the pipe and you can darned near measure anything you want: temperature, flow, pressure, or the dissolved oxygen content of the water!

Alternatively, think about the piercing saddle valves that are used for ice makers! I've never seen one leak, and that goes DIRECTLY into METAL PIPE. It ought to go through PEX, PVC or any other plastic pipe like a hot knife through butter! Again, you're essentially inside the pipe albeit with a piece of tubing extended from the pipe.

Just some outside-the-box thoughts - by getting inside the pipe

Regards,

Bruce Bates

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When all else fails, try inserting a new battery.

jmspaggi

Hi Bruce,

Thanks for your water refreshed ideas [noparse];)[/noparse]

So just imagine that I can insert something into the pipe and have it not leaking. What can I insert inside to detect if water if flowing (which will cost less than $50)? Any clue?

JM

Bruce Bates

JM -

I just spent 10 minutes on Google, and already I have THREE PDF's. You might try that avenue.

All I used for a search argument was "inexpensive flow meter". I was on the third set of hits when the last email came in.
I still have 7 more pages of hits if I were to continue

Regards,

Bruce Bates

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When all else fails, try inserting a new battery.

MSDTech

One idea you might look at is salvaging the flow sensor from a water softener. I've had two water softeners in the house that use the volume of water used to determine when to be recharged. In both cases, they had a turbine in the output line that measured the volume of water used. When I replaced the first it showed no leakage around the sensor. You might be able to salvage one off an old water softener and install it in your line. I believe the system used a turbine with a hall sensor, so it would be easy to interface with a BS2.

kelvin james

Assuming you need a " flow monitor ", this one just works as an on/ off switch with adjustable gph setting.

cgi.ebay.com/Chem-Tec-Adjustable-Flow-Monitor-CCM-015_W0QQitemZ350072080969QQcmdZViewItem



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jmspaggi

Thanks all for you hints and you help! The last link from Kelvin is exactly what I am looking for. I also found some vendors using google and Bruce recommandation. So I really think I will now be able to find something close to what I need, for a price under $100. whith is perfect for me!

Thanks againt for your help.

JM