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Old December 20th, 2007, 09:02 AM   #1
Viggen
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Flow Totalizer S7-300??

Hi there!


I have used the search button for help to find some solution`s
to make a totalizer for flow.
I did see many solution`s but all the answers are in STL.
Because i allways have been using LAD for programming the STL is greek for me.

Is it anybody that wants to make an example for totalizer in ladder??

input is 4-20mA
Flow rate 25000kg/h

ps. Sorry for my bad english


regards
Eivind
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Old December 22nd, 2007, 10:32 AM   #2
Flopro
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Here's a very simple and sometimes accurate enough way:

0 - 25000kg/h = 0 - 6.944kg/second

So: scale 4-20mA input to floating point value of 0 - 6.94kg/sec
Then: use 1 second timer to snapshot "sample" 0 - 6.94kg/sec floating point value and move/add it to another floating point register "Total."

Every second the total will grow based on the flow rate at that 1 second snapshot.

This is primative but works and CAN be optimized with the usage of scan time considerations and time slices but that's more complicated and PLC specific.
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Old December 22nd, 2007, 03:59 PM   #3
Pandiani
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This is my implementation.

I like using cyclic interruption blocks such as OB35 which is executed every 100 ms (default)
You have input 4-20 mA = 0-25000 kg/h
25000kg/h = 6.9444 kg/s = 0.69444 kg/(100ms)

So, first scale your input (in S7-300/400 it is integer range 0-27648) to 0 - 0.6944 with standard FC105

Second, just summarize current input value to current totalizer and that's it.

I'd like others to express their opinions about this solution.
Attached Files
File Type: pdf Flow totalizer.pdf (5.6 KB, 1196 views)
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Old December 29th, 2007, 06:31 AM   #4
Viggen
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thank you!

Regards:
From one who has to work in christmas time
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Old December 29th, 2007, 01:45 PM   #5
Pandiani
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Viggen, did you implement this solution in your program?
How does it work?
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