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Author Topic: How to calculate totalizer of water flow  (Read 5046 times)
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thetrueman
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« on: July 07, 2010, 07:52:45 07:52 »

Hi all,

Suppose water is flowing through a pipe and we've installed flow meter on the pipe. Sometimes flow is 10 liter/sec and sometimes 20 liter/sec and this is we can see on any gauge or meter.

I want to understand that how to measure total water consumption for a certain time i.e. one hour. Is this is done by any electronics way or micro controller programming? Please any ideas???

TheTrueMan
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jlb
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« Reply #1 on: July 07, 2010, 09:18:06 09:18 »

I suppose your sensor gives you the speed of the water in the pipe

So to get the amount of water flowing by second, you have to multiply this speed by the area of the cross section of the pipe.

Using a microcontroller, your may write a program that execute every n ms and get the current speed, multiply it by the cross section of the pipe to get the amount a water flowing in n ms. Accumulate these values to get the amont of water during a longer time.

You'll have to calibrate your sensor by doing measures with various speed.

Regards
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wakeke
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« Reply #2 on: September 05, 2010, 09:37:10 09:37 »

In addition, consider the cross-sectional area of the pipe..if it's too large for the water to fill in the whole area...if  it doesn't (some cases may be possible if pressure is too low) computing the cross-sectional area x speed might not be the total amount of water that was consumed or that passed through the sensor point.
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solutions
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« Reply #3 on: September 05, 2010, 08:24:18 20:24 »

I suppose your sensor gives you the speed of the water in the pipe

So to get the amount of water flowing by second, you have to multiply this speed by the area of the cross section of the pipe.

Using a microcontroller, your may write a program that execute every n ms and get the current speed, multiply it by the cross section of the pipe to get the amount a water flowing in n ms.
You want the cross sectional area at the sensor, not of the pipe.  You also have to ensure you have non-turbulent flow.

As was mentioned, you'll need to do a calibration at different flow rates, as boundary layer effects (zero flow at walls) will mess you up at lower velocities.  If you calibrate time to fill a bucket of known capacity (gallons, litres, hogsheads), then it's a lookup table and no calcs needed (unless you want to interpolate).
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Sun_rise_pt
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« Reply #4 on: September 06, 2010, 11:22:41 11:22 »

Thetrueman

Try the site of MCS electronics (Bascom). On the app. notes exist a good flow meter with all you need, except hardware... Wink
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frasenci
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« Reply #5 on: September 06, 2010, 08:17:12 20:17 »

Sometimes flow is 10 liter/sec and sometimes 20 liter/sec and this is we can see on any gauge or meter.
Hi thetrueman,

I see you already have the instantaneous water flow reading.
So, it is only a matter of adding up every x period of time.
According to how much the reading varies over time , you could do this every second, 30 seconds, 1 minute etc.

For example :

You take readings every second . Instrument is telling you 10 liter/sec x 1 sec = 10 liter
Next second same thing , reading in [liter/sec] x time elapsed  [ sec ]  = liter , yo keep adding the result to a totalizer in liters.

That is it.

Should your readings vary to much you can program to fire the reading and time elapsed with a window of values , say  9 <= reading <= 11 liter/sec. applying average values

Hope this helps

If the instrument you are using has some kind of interfase you can probably do this calculation and adition in an Microcontroller or Pc.

Greetings
Francisco
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