Analog to DINT

[sheperd9]

I'm working on a project where I have to take a reading of a +/- 5V Analog DC signal and convert it to a DINT for some calculations. I'm using a compactlogix controller and have most of the code written out but I can't figure out how this will work. Is there any reading I can do on something similar, or a similar project I could look at?

Thanks in advanced

 

[AustralIan]

I assume you have the data in a REAL.
You can use a Move instruction (MOV) to move the data into a DINT.
If you want to multiply the value first, you can use a MUL instruction, and just have the destination type a DINT.
eg. MUL REAL1 1000.0 DINT1

 

[sheperd9]

Thanks I will probably do the latter, because I have to do some converting after that. The inputs are LVDTs so I think there might be not be an exact number it will read at any given point. Do you know if there is any way around this?

 

[TConnolly]

From you earlier posts I'm guessing you are using a compact logix with 1769IO. The compact logix does not support scaling on the analog cards. You will need to scale your raw analog input with a CPT instruction, a ST statement if you have the ST extension, or with a scale function block if you have the FB extension. You could also download an SCP AOI or write your own to perform the scaling. Since you will be doing the scaling in the software then just make the destination your DINT tag.

 

[sheperd9]

You are correct, right now my scaling is just a simple

d := 39.3701*(.001*LVDT+.005); //A specific LVDT's compression in inches

Does that look plausible for my situation?