Duplicating AB SCP Command in another PLC

[thunderstrike]

How would you aaproach duplicating the Scale with Parameters command in another plc like EzAutomation Touch PLC of which they do not have any scaling so I assume it all has to be done in straight math. I am having trouble coming up with a good routine that works. Any help on that would be great.

 

[kamenges]

The SCP instruction just actively solves the equation for a line, which is Y = mx + b where, mapped to SCP instruction text:

Y -> SCP Output
m -> SCP ((Scaled Max. - Scaled Min.) / (Input Max - Input Min.)) (slope)
x -> SCP Input
b -> SCP (Scaled Min. - (((Scaled Max. - Scaled Min.) / (Input Max - Input Min.)) * Input Min.)) (y-intercept)

Keith

 

[thunderstrike]

I think you are missing something in your break down. I agree you first simple equation for slope, but your supplemental equations have something wrong. If I plug numbers in as follows:

Input Min = 5
Input Max = 100
Scaled Min = 32
Scaled Max = 60
Input = 25

m = (60-32)/100-5) = 28/96 = .305268
B = (32-(28/95))* 5 = 158.473685

So plug that into your first equation: Where 25 is my in.

y = (.305263 * 25)) + 158.473685 = 166.10526

This is greater the the input max so I know something is wrong...??

 

[kamenges]

You have your parentheses in the wrong spot.

It shouldn't be:

B = (32-(28/95))* 5 = 158.473685

It should be:

B = (32-((28/95)* 5) = 30.542

I added parentheses in places I didn't really need them for clarity. Apparently it didn't make things any more clear.

You can do this all in one fell swoop with substitution:

Output = Scaled Min. + (((Scaled Max. - Scaled Min.) / (Input Max - Input Min.)) * (Input - Input Min.))

after a little moving around of terms.

Keith

 

[Mickey]

See PDF below.

 

[Mickey]

And some more reading material ( by the Master) for your enjoyment. Which should complete
your understanding.

http://www.ronbeaufort.com/y=mx+b_part1.pdf

http://www.ronbeaufort.com/y=mx+b_part2.pdf

 

[504bloke]

( by the Master)

I think Ron Should change his Login / Username

The Master is Good Mickey !