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Flow Calculation

Created by: OmegaProjects at: 7/8/2009 4:58 PM (8 Replies)

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7/8/2009 4:58 PM	Rate (0)
OmegaProjects Silver Member Joined: 11/14/2008 Last visit: 1/22/2026 Posts: 504 Rating: (22)	Hi , I would like to know how I can program a flow calculation. I would like to know what the total flow is in one day , What is the most easy way to program this ? I prefer to use FBD , but other solutions are also welcome, Maybe I could use FC105 and a SF-Timer ? Thanks Eyup Y.
	Last edited by: Eyup at: 7/8/2009 5:33 PM
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7/8/2009 5:33 PM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 1/21/2026 Posts: 12481 Rating: (2722)	Hello Eyup; The critical part of any totalizing procedure is maintaining the constant time intervals between readings, so that you can integrate the flow volume correctly. The following FAQ suggests a standard way of doing this, and allows you to downl;oad a sample program you can use in your own program. http://support.automation.siemens.com/WW/view/en/23061633 Tke the time to study the principles behind the function so you can use it properly. Hoep this helps, Daniel Chartier

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This contribution was helpful to 1 thankful Users OmegaProjects

7/8/2009 5:38 PM	Rate (0)
Bhaskaran Posts: 107 Rating: (13)	HI ! Which sensor you are using and what is the feedback of this sensor ??? To find cumulative flow you can use a time interrupt OB since it has a defined time which is constant as compared to OB1 which can be vary. If you are getting an analog feedback say 0 - 10 V = 0 - 100 litre / min and you are calculating the cumulative flow in 100ms interrupt then you can proceed as follows - 1. Define a varible in the PLC as cumulative variable in float format - Say this varible is Z 2. Scale the analog input into the corresponding physical value (float) - Say this value is X litre / min 3. Divide this value ( X ) first by 60 to get litre / sec 4. Divide the above result further by 10 to get the value in litre / 100ms. - Say this value is Y 5. Now add this value (Y) to the cumulative flow variable (Z) and transfer the result to Z You can also use other time interrupts but depending upon the time value you have to adjust the factor used in point 4.
Bhaskaran Posts: 107 Rating: (13)
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7/8/2009 5:38 PM	Rate (0)
OmegaProjects Silver Member Joined: 11/14/2008 Last visit: 1/22/2026 Posts: 504 Rating: (22)	Dear Daniel , Thanks for your reaction , One question about it , Would this give me value after the Time interval has been passed away or will it give me a constant updated value of the previous 24 hours . I suppose it's the second thought of mine , because of I've seen a cycle time... Or am I wrong ? Thanks Eyup Y.

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7/9/2009 6:26 AM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 1/21/2026 Posts: 12481 Rating: (2722)	Hello Eyup; The totalized value will be recalculated every cycle time interval. If you want to read the value after every 24 hours period, use a time-of-day interrupt OB (such as OB10) to transfer the latest valuefrom the totalizer to some storage area at a precise moment of each day, or use SFC1 to read the Real-Time clock....' Hope this helps, Daniel Chartier

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This contribution was helpful to 2 thankful Users OmegaProjects Kucuk Tayyip

7/9/2009 5:06 PM	Rate (0)
OmegaProjects Silver Member Joined: 11/14/2008 Last visit: 1/22/2026 Posts: 504 Rating: (22)	Thanks a lot for your reaction again , It is nice to read the value after 24 hours has been passed away but I prefer to know how I can know the updated 24 hours by that I mean : for example : 12h00 --> 200 l / m^3 13h00 --> 220 l / m^3 actually it would "refresh" the passed 24 hours each hour by counting up the previous hour up and counting down the latest 24th hour . I do not know whether this is clear Thanks

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7/10/2009 8:41 AM	Rate (0)
Aret Posts: 2348 Rating: (265)	In the simpliest implementation- Supose ypu have array Flow[0..23] of real, each element contains flow by an hour, specified in index. I means Flow[15] would contain current flow at 15:00:00. Also you have Dayly_flow variable (initialize with 0.0) What you do - create OB1x calling each hour. In OB you do following: Dayly_flow := Dayly_flow -Flow[Index] + Current_flow; Flow[Index] := Current_flow; Index := (Index + 1) MOD 24; PS. Initialize Index withvalue of current hour 1 time (For ex/ in OB100). PPS. Solution is one of the simpliest - so have it's drawbacks, but easy to programm.
Aret Posts: 2348 Rating: (265)	Last edited by: Aret at: 7/16/2009 11:20 AM
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11/7/2012 9:01 AM	Rate (0)
KPawar Posts: 4 Rating: (0)	Dear Expert, I got sample Programm fromhttp://support.automation.siemens.com/WW/view/en/23061633 but it is in German Launguage. Could I will get in English Launguage. Attachment Totalizer.JPG (234 Downloads)
KPawar Posts: 4 Rating: (0)
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11/7/2012 9:09 AM	Rate (1)
RAJKIRAN Silver Member Joined: 8/18/2009 Last visit: 7/28/2025 Posts: 558 Rating: (33)	Dear Kpawar, You will get English comment inSource "Totalizer_e": with English comments. See attachment. Attachment Totalizer.zip (278 Downloads)
	Rajkiran Patil
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This contribution was helpful to 1 thankful Users KPawar

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