[KenWittlief]

Disar,

Please elaborate on the problem.

Is the spike causing a problem or could it only be something you are seeing on a scope that looks odd, but doesnt affect the process?

Is the spike at the start, near the end...?

Usually with a PID loop you will see rapid changes in the control signal, esp if you have a D with a large gain. Another place where spikes are introducted is when you first start the process, or you make a step change in the input signal.

Another posssiblity, we tend to think of PID control as if we have infinite response from our system, but real componets, like voltage amps for example, have a maximum output voltage, sensors have a max and min input. If one of your signals is hitting the max of an amp output, or a sensor input, then the PID equation starts to fall apart. Even if you are testing it open loop (with no PID feedback enabled), if you max out an amp or sensor, then very weird things will start to happen.

If you cant post details of your work you can send PM's to mentors on this forum and we can discuss things privately, or arrange an email converstation. If you are working as a co-op you can also consult with professors or TA's at school.

BTW, Engineering in Buffalo = SUNY Bflo?

Another thought, if this process uses a lot of power or voltage, you could have a ground loop or a sensor that is susecptable to nearby energy flow, or a poor ground path that spikes the sensor reading when current surges.