NORM_X function does not give correct values

Hi Guys,

I am using this function

#Normalized_Value := NORM_X(MIN := "DB_SystemSettings".Track_Percentage_Min,
MAX := "DB_SystemSettings".Track_Percentage_Max,
VALUE := "DB_Track_Control".Track_Percentage_Left
);

#Normalized_Value is a real
MIN=-100
MAX=+100
and "DB_Track_Control".Track_Percentage_Left (-100 to +100)

but I don't get any output between 0 to 1, which is supposed to be!!.

Has anybody encountered this problem? Any idea what is wrong?

my plc is S7-1200 and I am using TIA Portal V14

thank you for your support.

Can you change the Mina and Max display format of the monitored values to decimal and see if those are the values you intended. They're out to lunch.

kalabdel said:

Can you change the Mina and Max display format of the monitored values to decimal and see if those are the values you intended. They're out to lunch.

Click to expand...

Hi Kalabdel,

Thank you for your reply. Yes they are not the values I wanted. But why this is happening ?

Here is my data block. Do you see any problem there ?

Thank you in advance.

Mahdiar

You are not monitoring your data block, but DBD96 and DBD100 do not contain valid floating point numbers, hence your normx function is returning the input value.

The start values are as you stated but are the tags being used somewhere that the values are changed?

Why use the Norm_X when your value is already a percentage? Why not divide by 100.0?

Have you cross referenced those limit variables?

kalabdel said:

The start values are as you stated but are the tags being used somewhere that the values are changed?

Click to expand...

Hi Kalabdel


These are settings and for now they are just read for this NORM_X function. No other reference.

For now I have used

#Normalized_Value :=(100-"DB_Track_Control".Track_Percentage_Left)/200;

and it works fine. But I am still curious to see what was the problem. Since our tracks moved by accident and it was almost a close call to incident.

I have attached cross reference snapshot of the tags after I commented the NORM_X code and used constants instead. FYI.

Thank you for your support



Regards,
Mahdiar

cardosocea said:

Why use the Norm_X when your value is already a percentage? Why not divide by 100.0?

Have you cross referenced those limit variables?

Click to expand...

Hi Cardosocea,

thank you for your reply.
I did and they are not used anywhere esle. It is possible and basically I did that for now to solve the issue. This is what I am using now.


// #Normalized_Value := NORM_X(MIN := "DB_SystemSettings".Track_Percentage_Min,
// MAX := "DB_SystemSettings".Track_Percentage_Max,
// VALUE := "DB_Track_Control".Track_Percentage_Left
// )


#Normalized_Value :=(100-"DB_Track_Control".Track_Percentage_Left)/200;


But I am curious to find out what the problem was. It was a close call.
I have attached the cross reference snapshot FYI after i commented NORM_X.

thank you for your help.


regards,
Mahdiar

The monitored snapshots in your first post, we're they taken from the live CPU or a simulation?

You said it was a close call, was the software just deployed or has it been working for a while?

Is there any other non Siemens HMI or Scada or any communication of any sort that has access to the data?

This shouldn't be so mysterious, it's very straight forward. The values you showed us should work and all you have to do is simulate it to prove it and if it does the your code is fine and then either the code on the CPU is different or has been modified or something exterior is changing those values.