A/B PLC 5 Non-Linear Analog output

I am in need of creating a Non-linear analog output based on a linear (0-100%) input signal. I have an old version of programming software (A/B 6200 series release 4.3) an I am having a hard time figuring out how to accomplish this through this software platform. I understand the newer platforms make this task easier but Upgrade is not an option. Any information leading in the direction of accoumplishing this task would be greatly appreciated.

Thanks

JP

what kind of equation/function do you need to create your output?

Equation?

The linear input signal (0-100%), needs to be translated to a valve postion output signal, the signal need to match the flow curve of the proportional valve, I cannot identify a equation that will do this. The flow curve is not linear at all.

have you collected any data that you could post? (example: 10% input = 4% output; 11% input = 5% output; etc.) ... and how much resolution do you require? (example: would 100 points be enough?) ... also, you need to tell us what hardware you're using (example: PLC-5/20, 1771-IFE input module, 1771-OFE2 output module, etc.) ...

Hi, there:

I am believed that by dividing your output and input into small segments and using different logic with compare and other math function, it should be OK. The only thing is you have to sample enough data from process.

Hopefully this can help you.

Best regards,

Jason

Ron has the right idea

You could make a piece wise linear look up table.
I don't like look up tables because they are usually harder to code
and slower than computing formulas in ladder.

Calculating the formula takes more work up front though.

The are a few mathematical techniques that can be used to compute the formula from a bunch of points. 100 may be overkill. 10 is probably enough unless there are a lot of inflection points.

If you are serious then supply the points in CSV file so it can be easily imported. It is also easier if the points are space a even increments like 10% or 5%.

Look up least squares identification.

If you are using a pipe with a proportional valve, then I wonder if you could use the simple circular-area equation.
Output = 3.1416 x (input)2

I'd say why bother with math if function is not simple.
Just use lookup table. For valve position it should be ok to
use some 100 points (or more if you want to):
- Create file such as N100 with 100 elements.
- use SCP to scale your signal 0-99 into say N7:10
- use N7:11 as output (you can scale it to whatever you want to
before sending it to output)
- use MOV N100:[N7:10] N7:11 to read lookup table.
- Get a large cold beer and smile at people patting your back.