Dear All,
            I would like to thank Mr.Russell McMahon, Mr. Marcel Du Champ and Mr.Sergio for their kind help. I was successfully able to develop the PIC based ORP circuit. I am sorry that I was not able to thank them earlier since I have a very restricted access to the internet. 

I am currently trying to use the same op amp circuit to modify such that I am able to read signals from probe between -2V to +2V. I wanted to level shift the signal such that I am able to read the signal against a scale of 0-4V. I removed the 40K resistor and I replaced the same with a 10K resistor such that my opamp gain is 2 in the first stage. Now when I set an offset voltage such that my output is 4V for a -2V input, I see that I am not able to find linearity in the output. When I provide a 2V input to my opamp, the output reads zero. When I provide a -1V input to my opamp, the output is close to 3.81V and 4.1V for     -2V. Have I adopted a wrong technique for level shifting my signal? Please find the circuit diagram in the link given below:
http://mechatronicscraze.files.wordpress.com/2010/03/orp-circuit1.jpg

Please correct me if I am wrong.

Yours Sincerely,
Sairam


      
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist