nonlinear scalling for analog signal

dchartier

Hello maher;
If you are dealing with a non-linear signal, and you cannot use a linear section of the curve for your purposes, then you must use some form of linearization, or using a look-up table (for very non-linear curves).
Linearization means approximating the curve as small sections of connected lines, for which you calculate the slope, which you then use to find the value of the point you want to evaluate.
Siemens offers a solution (not free,but the principle is explained so you can use it as a template for your own program if need be):
What should you watch out for when using a resistance thermometer that is not in compliance with DIN standards?

With enough information from the sensor datasheet, you could use the technic=que described in this post from the Web to do your calculations:
Non Linear Sensor, how do I make a conversion?

The lookup table technique requires more work, but it is simpler: you have to create a table representing the (x,y) value for all points in the curve (you must determine the intervals acceptable to you) and use a loop compare instruction to locate the nearest x point, using then the linked y value as your scaled input.

Hope this helps,
Daniel Chartier

At the first of all, thank you Mr. fritz for your advice and i am so sorry for the previous replying because i have spent a lot of times to find out the answer a round this subject but i've failed so i was disappointed.

and special thanking for Mr. dchartierbecause he is following up a lot of subjects with me.

Best Regards,

Maher

mmaher

Hi TAGOLOVER,

where is this block please ( in which library ) because i don't have in my library (modpid )?

you ment i can transact with nonlinear analog signal by PID ( FB15 ) that's right?

thanks in advance,
Maher