Pease HELP with simatic step 7

I would be very gratefully if somebody vould help me…



Im trying to learn STL programming in simatic step 7 and I got one learning task that I don’t know even how to start solving L



We have one pipe in wich is steam with the pressuere from ccc 20-30 bar.

On this pipe there is a water colling device regulated with valve.



I should make DB with steam saturation tablle (temperature and pressure of steam for saturation point), and STL programme wich should for measured pressure and temerature of steam compare is the temperature of steam bigger that temeperature of saturation temperature for that measured pressure (from DB table).

The problem is also that in the table should be pressure for ccc 20, 21,22..30 bar and the temperature for that and the values for the pressure beetwen for example 22 and 23 bar should be linear interpolated.



Does anybody have a idea how to make this? Im just start to leard PLC programing and for now I don’t have somebody to ask…

thnx

There are table functions in the library (TI library if i remember well) , you can seach for the temperature in this table the result would be an index

use the index and indirect addressing to see corresponding value

good luck

The function Amr Hassan mentions is FC103. I can't remember off-hand exactly where it is stored, but it's somewhere in the Standard Library.

If you search for "CDT FC103" you'll find an old Thread of mine which discusses some of the problems I had working with FC103 and you'll also find there a rewritten version of it by S7Guy which does everything, but is a bit neater and easier.