Post by thread:[EE]: detect waterflow

Didn't think of that, what kinf of a microphone goes well with water? /patrik ----- Original Message ----- From: "Mark Newland" <spam_OUTapeTakeThisOuTESKIMO.COM> To: <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> Sent: Tuesday, May 08, 2001 6:42 PM Subject: Re: [EE]: detect waterflow {Quote hidden}> Microphone > > Patrik Husfloen wrote: > > > Are there any clever ways to detect waterflow in a hose/tube? > > > > /Patrik > > > > -- > > http://www.piclist.com hint: The list server can filter out subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

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}

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" <syatesKILLspamCARETECHNOLOGIES.COM> To: <.....PICLISTKILLspam.....MITVMA.MIT.EDU> Sent: Tuesday, May 08, 2001 6:49 PM Subject: Re: [EE]: detect waterflow {Quote hidden}> 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}

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 -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Doh! :) ----- Original Message ----- From: "James R. Cunningham" <EraseMEjrcceaspam_OUTTakeThisOuTBELLSOUTH.NET> To: <PICLISTspam_OUTMITVMA.MIT.EDU> Sent: Tuesday, May 08, 2001 8:26 PM Subject: Re: [EE]: detect waterflow {Quote hidden}> 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 ----- > > From: "Mark Newland" <@spam@apeKILLspamESKIMO.COM> > > To: <KILLspamPICLISTKILLspamMITVMA.MIT.EDU> > > Sent: Tuesday, May 08, 2001 6:42 PM > > Subject: Re: [EE]: detect waterflow > > > > > Microphone > > > > > > Patrik Husfloen wrote: > > > > > > > Are there any clever ways to detect waterflow in a hose/tube? > > > > > > > > /Patrik > > > > > > > > -- > > > > http://www.piclist.com hint: The list server can filter out subtopics > > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > -- > > > http://www.piclist.com hint: The list server can filter out subtopics > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > > > -- > > http://www.piclist.com hint: The list server can filter out subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

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_SwintTakeThisOuTbaylor.edu ----- Original Message ----- From: "Patrik Husfloen" <spamBeGoneu58611234spamBeGoneTELIA.COM> To: <TakeThisOuTPICLISTEraseMEspam_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}> > Thanks. > > Patrik > > > ----- Original Message ----- > From: "Shawn Yates" <RemoveMEsyatesTakeThisOuTCARETECHNOLOGIES.COM> > To: <PICLISTEraseME.....MITVMA.MIT.EDU> > Sent: Tuesday, May 08, 2001 6:49 PM > Subject: Re: [EE]: detect waterflow > > > > 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}

> 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, EraseMEolinembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> >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. -- Dave's Engineering Page: http://www.dvanhorn.org Where's dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9 -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

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 -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

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}>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. 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 RemoveMErayEraseMEEraseMEdsp.com.au [ 2001 ] -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

>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) -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

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 > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

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 > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

> 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. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, RemoveMEolinspam_OUTKILLspamembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

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 -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspamspamBeGonemitvma.mit.edu

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 -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestKILLspammitvma.mit.edu