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TOT Instruction

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I have an existing machine that pulls several rolls of film through it and executes a sealing process. The machine has a scaled feedback value (Tag: Velocity, Type: REAL). No one knows for sure what the engineering unit is (inches per second, feet per minute, etc.) of this tag. The supervisor wants to add an accumulative length counter based on this feedback value. The purpose is to have some idea of the total amount of film run through the machine for comparing to the total pieces of product produced. A colleague suggested using the TOT (Totalizer) function block or structured text instruction in a timed task. But the instruction itself has a timebase for execution control. I've searched the forum but cannot find anything related. Anyone have experience doing this or something similar? Or perhaps use a different instruction? The processor is a CompactLogix 5730-L18ERM. I just received the project specifications today and the due date is next week. (Of course!) So there is no time to research, design, purchase, install additional hardware. No pressure here! Haha.

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Given you're using the L18ERM this in it's simplest form is realtively easy.  Drawing from Physics-101 remember that D=RT where D=Distance, R=Rate and T=Time.  Given that the L18ERM programs in Studio 5000 and supports periodic tasks, you jsut need to create a new periodic task called Film_Totalizer for example.  Then set it's period to 10 or 100 or 1000 ms. Then create tags for PeriodicDistance and TotalDistance of type REAL.  You can use the tasks Period times the Velocity to get your periodic distance and TotalDistance plus PeriodDistance to get the new TotalDistance.  Obviously based on variation and performance you'll want to adjust your period.  IF you can determine the unit of velocity you'll be able to get even more accurate.  This is how I'd approach it given the 11th hour Scope Creep request.

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