thermocouples

120 degrees in the same plane (circular), especially if there has not been sufficient thermal mixing of the process at the point of measurement. In this case, the average of the temps should be used for control (as opposed to the middle of 3) in addition to any deviation checking used to detect a failed TC.

If any thermal streaming is occurring, then mounting the TCs linearily down the pipeline reduces your chances of measuring it.

This approach may be overly cautious depending on your application, but this was a real world headache for me that I thought I'd share.

Agreed and complete answer