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Old September 16th, 2020, 05:11 PM   #1
Robb B
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Totalizing volume with a level transmitter

Is this reasonable to do?

I am using a SLC 5/05 so there's no totalizing instruction, I think I have to make my own. Anybody done this, any starting points to consider?

To make it even more fun, the receiver tank may or may not be emptied during the cycle, and may or may not have leftover from a previous cycle.
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Old September 16th, 2020, 05:25 PM   #2
Ken Moore
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Usually totalizers are used with flow meters. Is that what you have?

Using a level transmitter, you should be able to calculate the volume based on the current level. You will need the tank dimensions and a little math.
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Old September 16th, 2020, 05:26 PM   #3
Lare
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Calculated volume change.


It depends if tank is filled before emptying or filled same time than emptying.

Now as it same time emptyed and filled, you need to know both level change and output flow to outside from tank same time. (Volume = flow out + level change * tank bottom area)

If both filling and pumping out is same speed, level never changes and it makes everything more fun.






Is emptying allways with same flow or is flow changing all time?

(If speed / flow is constant, you can forgot level change and calculate only pumping time (s) * flow litres / s = volume

Last edited by Lare; September 16th, 2020 at 05:35 PM.
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Old September 16th, 2020, 05:36 PM   #4
Robb B
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Quote:
Originally Posted by Ken Moore View Post
Usually totalizers are used with flow meters. Is that what you have?

Using a level transmitter, you should be able to calculate the volume based on the current level. You will need the tank dimensions and a little math.
No flow meter, I believe it's a magtech level transmitter. I can get the volume okay, it's how to add it that I'm not sure on. Obviously the ADD instruction, but how can I use the max value before it gets emptied? And then add that to the next quantity, and so on.
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Old September 16th, 2020, 05:42 PM   #5
Robb B
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Quote:
Originally Posted by Lare View Post
Calculated volume change.


It depends if tank is filled before emptying or filled same time than emptying.

Now as it same time emptyed and filled, you need to know both level change and output flow to outside from tank same time. (Volume = flow out + level change * tank bottom area)

If both filling and pumping out is same speed, level never changes and it makes everything more fun.






Is emptying allways with same flow or is flow changing all time?

(If speed / flow is constant, you can forgot level change and calculate only pumping time (s) * flow litres / s = volume
The source of condensate is from a vacuum cycle, so the flow will be irregular. In addition it may be repeated several times until no more condensate accumulates. I will be adding an input signal to the PLC for when the tank is drained by a valve.
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Old September 16th, 2020, 05:50 PM   #6
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Old September 17th, 2020, 03:17 PM   #7
Robb B
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Well I think I have an in-progress solution. I think it is simpler than I was considering. For whatever reason I can't add pictures from this location (IT issue I think) but basically it's just moving the calculated volume to a register, then adding the moved volumes each time the tank is drained (can't add to the tank while draining, since it's part of a vacuum circuit). Then I just have to program it to deal with operator errors...
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