Analog Scaling

Hi, all.

I need some help with an analog scaling algorithm.

Basically, I have a digital signal that's 0 to full scale, which correlates to 0 - 10000 on my PLC.

My full scale values are 2.5, 4, 6.5, 10, and 15.

Basically, I'm trying to make a simple statement that depending on which full scale I am at, I can increase a value by 0.1 at a time, and it correlates to my 0 - 10000 count signal.

Standard questions:
What brand and model PLC?
Are you using Ladder, Structured Text or Function Block?
Is this a Homework Assignment?

Bullzi said:

Standard questions:
What brand and model PLC?
Are you using Ladder, Structured Text or Function Block?
Is this a Homework Assignment?

Click to expand...

This isn't a PLC like Allen Bradley or Siemens. I am using a custom device that has a standard Modbus RTU protocol built into it. I am connecting it to a HMI and rather than doing a bunch of hide and show functions on the HMI; I was hoping to use a macro built into the HMI and a local parameter, and then translate accordingly.

Which custom device and which language? Which HMI?

Bullzi said:

Standard questions:
What brand and model PLC?
Are you using Ladder, Structured Text or Function Block?
Is this a Homework Assignment?

Click to expand...

Diameter157 said:

Which custom device and which language? Which HMI?

Click to expand...

If is using a Maple Systems HMI.

This may not be correct but with limited information given . Map range comes to mind. Here's a quick Google link.

http://stackoverflow.com/questions/345187/math-mapping-numbers

Cheers
Marcus

Sorry I don't know maple HMI. Some HMI's have linear scaling built in I think. Myself I have always done it in the PLC because there are built in functions already that do it.


As mysum says, if your PLC doesn't already have such a function, you could easily write one using basic maths. Google "linear equation" or use this web calculator

If I understand you correctly you want 0-10000 to scale to 0-2.5 for example.

Your equation would then be : y=4000 * x + 0

So you would times 0.1 by 4000 to get your 0.1 value on the 0-2.5 to scale to 0-10000