Electronic Water Meter: A few questions

[NJ Roadmap]

I'm doing a design study on flow meters for water utility use (i.e. to be installed in households), and have some questions that I hope someone can answer:

1.what is the diameter of the pipe that comes into a household (I'm guessing 1 1/4 inch?)

2. what are typical max flow rates in households? and typical maximum water pressures?

3. does anyone know much about what technology is most common in utility flow meters: mechanical (turbine, oscillating piston, nutating disk etc.) or electromagnetic? (I know that ultrasonic is out of the question because of costs and the fact that it's too accurate for this application)

I'm proposing a meter which will make rate measurements (supporting electronics will be decided based on the measurement technique), convert it into volume and subsequently into quantity in litres. I propose that a PIC be used for the purpose.

I also need to implement AMR (Automatic Meter Reading), but am not sure of which technology would be best for data transfer (it doesnt have to be always-on or fast) so it could be PSTN (landline), RF, power-line or a GSM-based network. What would you choose?

Personally I'd go with PSTN, just because it's cheap and the infrastructure is already in place. GSM would require expensive GSM modules (I dont think it's feasible when 27 million such meters are needed). RF and power-line (as much as they enable easy installation) need to network infrastructure which is not in place. Any thoughts?

Happy New Year!

p.s. I'm not very good with my mechanical engineering as I'm an electronic engineer, so ANY help with the first 3 questions would be very beneficial!

 

[fingaz]

Hi,

I can answer the first question no problem. . . incoming water supply in the uk is usually 15mm diameter copper pipe (though I have seen 22mm pipe used)

ufortunately, I can't help with the other questions. . .

 

[NJ Roadmap]

Cheers fingaz. Appreciated.

 

[stevez]

Here in the US the typical water line is 3/4" for residential service unless fire protection sprinklers are installed (more of them all the time). A pressure regulator is often provided to keep pressures below 65 psig - but only when pressures are regularly above that. IM me if you need more information and I'll give you my email address at work. All of my references are there -won't be there until 1/2/07.

 

[NJ Roadmap]

Cheers for that. Just IM'ed you.

Does anyone have any thoughts about what would be a cheap and reliable method to get data from homes to datacentres for billing? I was thinking a 56k modem on the meter hooked upto a landline at each household premise, dialling a toll-free number with the datalogging servers at the other end.

 

[ikalogic]

I am a mechatronics student. we do a lot of fluid dynamics too.. i don't know if you'll need this, but that what we learn!

flow through pipes differs from country to another, but it should be between 2 and 4 meters per second.. to calculate the volumic flow rate, you need to have the coeeficient of discharge (Cd) of the pipe (a constant between .5 and .8)
then the volumic discharge Q =

Q = Cd * Area_of_pipe * velocity

Now if you are able to meaure velocity, you can deduce the Cd of any pipe with this experiment:

- take a bassin, of known volume,
- start a stop-watch, and let the water flow from the pipe into this bassin, until its full, then stop the time.
- calculate the volume that should be in the bassin using:
Volume = Velocity*time*Area_of_pipe,
- the coeefefient of discharge is equal to: Volume of bassin / Calculated volume.

all this to tell you that, you cannot bill people only knwoing the velocity of water and the diameter of their pipes.. yould be cheating them! the real volume getting out of the pipes is less than what you calculated. that's why we use the Cd constant.

 

[Nigel Goodwin]

Cheers for that. Just IM'ed you.

Does anyone have any thoughts about what would be a cheap and reliable method to get data from homes to datacentres for billing? I was thinking a 56k modem on the meter hooked upto a landline at each household premise, dialling a toll-free number with the datalogging servers at the other end.

What about houses without landlines?, there are getting to be more and more of them - in fact I would have been one of them, but they eventually managed to proviode me broadband (but not until they changed the specification). As it was I was waiting for radio broadband to reach me, then I would have cancelled my landline and relied on a mobile phone.

 

[NJ Roadmap]

I did think about that, but it's a very small percentage. So in those cases the 56k comms module can be swapped for a GSM module.

 

[Andy1845c]

What about houses without landlines?, there are getting to be more and more of them.

Yep, I would be one of them. I went as far as removing the wiring from the side of my house when I painted it this past summer. I think as more of my generation (20 somthings) buy houses, more landlines will disappear.