Water Flow Meter with one pulse per gallon

[mhowasso 5]

Hi All, Im trying to find a water flow meter for a 1/2 inch line that turns on and off, that when on has a flow rate of about 1 gpm. It is not always a full pipe and it only turns on for about 10 seconds every 10 minutes. I would like to get one 24vdc pulse out for every gallon thru meter. Just curious if anyone has used a meter in this sort of application with good results and what brand/model of meter it was or any suggestions. Thanks

[TimWilborne 108]

If you don't always have a full pipe of water then it is not going to be accurate. Almost all flow meters depend on a full pipe to read properly. What makes the pipe drain? Could you add a check valve or something to keep it from draining? What type of PLC are you using? What is the gallons per minute that will be going through the flow meter while it is running for that 10 seconds. Normally you see them connected to some type of high speed counter, but if it is slow enough you might get away with a regular input.

[mhowasso 5]

I can put it on the front side of the solenoid, that will keep it a full pipe. I am using a AB MicroLogix 1400. When the water is flowing it is about 1 to 2 gpm.

[TimWilborne 108]

1 or 2 gpm on a 1 pulse per gallon isn't going to accurately register during a 10 second opening. Are you just using it for a totalized value over months or are you trying to control your solenoid with it? Anyway, I would configure one of the ML1400 inputs as a high speed counter with a mode of up counter. You do this in the RsLogix function files

[mhowasso 5]

I know how to connect it. Im just using it as a long term totalizer. What Im looking for is a brand/model of flow meter. Edited 9 Dec 2012 by mhowasso

[TimWilborne 108]

Is it just tap water? I see these used for basic totalization a lot. About as simple as it gets and gives you a local "display" http://www.omega.com/pptst/ftb8000b.html

[Conor 4]

I have used these before, but they need the full pipe as well http://www.ifm.com/products/us/ds/SU9000.htm

[OkiePC 14]

I think you are looking for two (or more) devices: 1) solenoid valve, normally closed. This takes care of turning the flow off and on. 2) flow meter with discrete output to give apx. 1 pulse per gallon. 3) flow control valve to regulate flow rate to apx. 1 gpm. The flow meter will only give you the pulses or readout, not start, stop or regulate the flow. We use the GPI turbine flowmeters with an analog output to a SLC for totalizing small batches of water added to some products. They are handy to install inline being battery powered and only need a small cable to connect the output signal.

[mhowasso 5]

Hi Paul, 1. I have a solenoid that turns the water on and off. 2. I have a flow control valve (adjustable) for the water flow. What I need is a flow meter to give a signal out to my PLC so I can keep track of my total water usage. Also, Im kind of limited on space, because of where this needs to mount. It is on a 1/2 inch copper line, and is only city tap water. The water is off more than it is on tho (solenoid turning on/off). I would prefer a simple 24vdc pulse out for every gallon that has gone thru the flow meter if possible. But right now Im open to any suggestions. Thanks

[OkiePC 14]

What kind of accuracy do you need? The GPI units are simple, cheap, and easy to deal with, but not highly precise. I think in practice they are +/- about 2%. http://catalog.gpi.net/Asset/920708-3_revE_G2_turbine_housing.pdf http://catalog.gpi.net/Asset/920709-05-revF-Industrial-09-Computer.pdf We use the analog output option of the flow computer but it does offer a pulse output as well (which should be more accurate and much simpler to program).

[kaiser_will 65]

Accusonics built a custom flowmeter for an application of mine some years ago that was similar. We needed to monitor and totalize stormwater runoff, thus the pipe would be partially full at many times. http://www.accusonic.com/default.aspx?id=33

[mhowasso 5]

Thanks for the Accusonics info. I have used these in the past, but I think for this current application it is a bit of an over kill. I did contact GPI and did not get much help. Is there a particular model that would work with a MicroLogix 1400 normal DC input ??? 1/2 inch line , 1-10 gpm Thanks

[OkiePC 14]

I would sure think that a ML1400 whould be able to reliably detect a net (after device variances) pulse width greater than 3-5 ms depending on how busy it is. How about one pulse per 0.01 gallon, at 10 gallons per minute thats 1000 pulses per minute, 16 pulses per second. 1/x gives 0.0625 full pulse time or about 30 milliseconds on and 30 off dependent on device repeatability and other factors. Or, go with one pulse per 0.1 gallon and have a 300ms pulse. that would be a piece of cake for the slowest of PLCs. My last ML1500 program runs in less than 2ms. They are quick, but consult the manuals for specific input and output latency and repeatability. EDIT: That doesn't seem right, someone double check me. I think I can find the books for you on their website, maybe tomorrow when I am at work with faster web. Paul EDIT: Or now. Pulse Access Module (Digital Open Collector Signal) Part # 125060-1 http://catalog.gpi.n...09-Computer.pdf http://www.besflowme...ter-Modules.pdf Looks like with up to a 750 Hz pulse, you would need to use the HSC feature (1.3ms pulse) But reading the standard electronics book, pin J2 is a pulse output. So perhaps that board is just basically a connector kit for it? Edited 31 Dec 2012 by OkiePC

[mhowasso 5]

Paul, I am using a ML1400 PN: 1766-L32BWA I talked to Matt at GPI and he told me to buy the following from them. G2S05NXXXXA = Turbine Meter 113435-1 = Electronics GPI told me this will give 2500 pulses per gallon (42 - 420 Hz). I have the flow meter connected to I:0/0 HSC and setup per AB tech note for using the HSC. How do I determine the total gallons for my totalizer..??? Im sure it is easy, but Im not seeing it. Thanks, Mark Edited 2 Jan 2013 by mhowasso

[TimWilborne 108]

Your count will be in HSC:0.ACC. You can your the DIV instruction with a source a of HSC:0.ACC and a source b of 2500 to determine your gallons