Hello there

programming in SCL

My main OB is just  :  CALL fc1

and function 1 is :

"Y0":=0.45;

"X0":=0.2;

"r1":=0.35;

"r2":=0.6;

"r3":=0.62;

"c1":="r1"**2+"Y0"**2+("X0"+"r3")**2-"r2"**2+2*("X0"+"r3")*"r1";

"c2":="r1"**2+"Y0"**2+("X0"-"r3")**2-"r2"**2+2*("X0"-"r3")*"r1";

All the variables are real . c1 is different from c2 inside the ( ).  My question is : when i run it on my s7-300 plc like this and when i run the same program with the only difference c2 is above c1 ,i get different values from the first program. ???????????

stavrina

Hello there

programming in SCL

My main OB is just  :  CALL fc1

and function 1 is :

"Y0":=0.45;

"X0":=0.2;

"r1":=0.35;

"r2":=0.6;

"r3":=0.62;

"c1":="r1"**2+"Y0"**2+("X0"+"r3")**2-"r2"**2+2*("X0"+"r3")*"r1";

"c2":="r1"**2+"Y0"**2+("X0"-"r3")**2-"r2"**2+2*("X0"-"r3")*"r1";

All the variables are real . c1 is different from c2 inside the ( ).  My question is : when i run it on my s7-300 plc like this and when i run the same program with the only difference c2 is above c1 ,i get different values from the first program. ???????????

 Dear staverina

For such a problem you need to monitor both the FC with call up path and nedd to see whats going on inside and you will be able to diagnose the problem 

stavrina

Hello there

programming in SCL

My main OB is just  :  CALL fc1

and function 1 is :

"Y0":=0.45;

"X0":=0.2;

"r1":=0.35;

"r2":=0.6;

"r3":=0.62;

"c1":="r1"**2+"Y0"**2+("X0"+"r3")**2-"r2"**2+2*("X0"+"r3")*"r1";

"c2":="r1"**2+"Y0"**2+("X0"-"r3")**2-"r2"**2+2*("X0"-"r3")*"r1";

All the variables are real . c1 is different from c2 inside the ( ).  My question is : when i run it on my s7-300 plc like this and when i run the same program with the only difference c2 is above c1 ,i get different values from the first program. ???????????

 Similar Problem I have faced ,but there I was compare two values ,mathematically both were same but when I compare (==) it was not successful.

huggy_d1

What is the difference between the two versions?  Perhaps it is simple round-off error?  Are  you saying it is like they are solving completely different problems or the round-off is slight but not negligible?

Change all your values to LREAL and compare the results.

 

stavrina

Hello there

programming in SCL

My main OB is just  :  CALL fc1

and function 1 is :

"Y0":=0.45;

"X0":=0.2;

"r1":=0.35;

"r2":=0.6;

"r3":=0.62;

"c1":="r1"**2+"Y0"**2+("X0"+"r3")**2-"r2"**2+2*("X0"+"r3")*"r1";

"c2":="r1"**2+"Y0"**2+("X0"-"r3")**2-"r2"**2+2*("X0"-"r3")*"r1";

All the variables are real . c1 is different from c2 inside the ( ).  My question is : when i run it on my s7-300 plc like this and when i run the same program with the only difference c2 is above c1 ,i get different values from the first program. ???????????

 

 well it seemS it's different. In any other programming logic the problem is the same ( i mean its the same if you compute the c1 first and then the c2 or the other way ). But here something is going on ... I don't remember the option LREAL in the Tia V11.

Hi!

As huggy_d1 said, it is probably a round-off error coming from the way real numbers are represented in memory. Could you share a print-screen with us?

Also, check this thread:

https://support.industry.siemens.com/tf/cy/en/posts/comparing-real-numbers/143136?page=0&pageSize=10

Hi stravina, i think you  must have an error in some place of your code,  it may be useful if you take a SS from your variable table...

Have you checked the real result of the operation?

C1 = 0.0634  or   0.0633999

C2 = 0.4354

I can see that some numbers are quite different... you can make a test code, as the following image, making that operation in 4 steps, checking every result and looking where the error starts. Use a calculator if possible.