Analog Scaling

Hey guys

I have an instrument that reads a 1-5 v analog value back.


My PLC only has a 0 - 10V analog option

The PLC reads -27648 to 27648 int values

Any ideas on how i could make this work.

Thanks team

You should be able to use a scale function if you have one available in your PLC. If not you could use a compute function.

if your span is 55297 for 0 - 10 V then

1 V = (-27648+5530) = -22118

5 V = (-27648+27649) = 1

Scale your output from -22118 to 1 for 0 to 100%

(RSlogix500 Ex. using scale with parameters function:

SCP I:1.0 -22118 1 0 100 N7:0

)

Don't know what PLC your using, but I would just use a built in scale instruction if it's available or role your own. Any hardware that you buy for scaling signals is doing the same thing that you can do in logic. At least when your talking about going from 0-5 to 0-10 volts.

If you need to roll your own you can find many threads here that cover ways to do it.
My preferred way of tackling the problem is to use Y=MX+B

y=mx+b
m=(y2-y1)/(x2-x1)
b=y1-(x1*m)
x1=input min.
x2=input max.
y1=scaled min.
y2=scaled max.
x=input value
y=scaled output value