Scaling

dcam · Mar 2, 2020

thought that might have been what he meant...thanks sir

PLCnovice61 · Mar 3, 2020

Thats the one, Ken. But if the code was done from the drawing it wouldn't know which was the input.

dcam · Mar 3, 2020

Fixed the analog block.

I do not want to lead anyone astray.

drbitboy · Mar 3, 2020

Code:

                 (CalVal – CalLowVal)
 MeasuredVal  =  -------------------- x (MeasuredDN – CalLowDN) + CalLowVal
                  (CalDN – CalLowDN)

It may not be obvious, but dcam's SCL (Scale) function block inputs and outputs map to my equation (above) as follows:

Code:

      In => MeasuredDN
InRawMax => CalDN
InRawMin => CalLowDn
 InEUMax => CalVal
 InEUMin => CalLowVal
     Out => MeasuredVal

And just to be clear: even if my concept of "scaling is multiplying by one" does not resonate, understanding proportions is a fundamental necessity for solving this problem correctly; so the OP needs to intimately and completely understand the equation above, and where it comes from, or else they should pass the task on to someone who does.

Ron Beaufort · Mar 3, 2020

I might be wrong - but I've got a hunch that some of our members might misunderstand what is being shown in Post #18 ...

the picture shown there is not a "flow chart" type of drawing - that would be followed while writing "the code" ... that picture IS the code ... if you're not familiar with it, you might want to look up Function Block Diagrams ...

here's a handy link for anyone who's interested ...

https://literature.rockwellautomation.com/idc/groups/literature/documents/pm/1756-pm009_-en-p.pdf

drbitboy · Mar 3, 2020

Ron Beaufort said:
I might be wrong - but I've got a hunch that some of our members might misunderstand what is being shown in Post #18 ...

I for one got it.

Shoot, to my mind every instruction on a rung, every function block, and every line in ST, is, in a metaphorical sense at a minimum, some form of "multiplying by one."

ndzied1 · Mar 3, 2020

Looks like the OP has gone AWOL on this one... Wondering if he was helped or scared away?

PLCnovice61 · Mar 3, 2020

Hi Ken, if you may have thought by my previous post that l thought that was a flow chart drawing, that is used to assist in writing the code, that's not the case. I am well aware of function blocks and how they are wired. I just like things to be precise and unambiguous.
Unfortunately dcam's FBD page could lead to some confusion to the less experienced, thanks dcam for rectifying the FBD wires/gaps.

Scaling

dcam

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PLCnovice61

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dcam

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drbitboy

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Ron Beaufort

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drbitboy

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ndzied1

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PLCnovice61

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