PID Troubleshooting

[Disar]

While there is a wealth of threads on PID's and have searched many of them. I could not find an answer to my problem.

I am currently working on implementing a PID algorithm. We are using a PID algorithm to control the flow of voltage or current during anode formation (for capacitors that my company manufactures).

We use an ATOM chip (based of a 16F876 PIC) and program in MBASIC (a variant of BASIC). I am unable to post any code do to confidentiality.

Our PID algorithm spikes during operation. It does so after the the response has been leveled. I am unsure whether it is periodic (not likely though) and as to what is the cause. We found the spike b/c we use Labview to collect data periodically during operation.

I am new to PID's and have just read "PID without a PhD" and other articles regarding PID algorithms. The code I am working with is one I have inherited from my supervisor who in turn inherited from someone who no longer works for our company (and who did not use a PID algorithm to control this process but he still got spikes during his operation, my supervisor used his code as a foundation for his PID algorithm).

I am a student in my final year of studies (EE). I am trying to determine the source(s) of this spike and how to remedy it. I would like to know if anyone has any troubleshooting tips I could try or any helpful hints.

Note: Rewriting the code is an option and is one I think I may try. But I would like feedback first before I decide to do so.

Thanks!