If you tune PID control loops by trial and error, or even if you tune them using a scientific method, give my PID Loop Analyzer a try. The following description comes out of its documentation: About PID Loop Analyzer.
PID Loop Analyzer is a software tool designed to help you optimally tune your control loops with very little process disruption. You perform an open loop bump test on your production loop and provide the test data to PID Loop Analyzer, and it models your process and suggests PID tuning parameters based on Lambda tuning rules. It allows you to select safe settings from aggressive to conservative. Do you want quarter decay response instead? No problem! You can now tune your loops using Z&N’s Ultimate method without putting your production processes into sustained oscillation!
It currently supports first order plus dead time processes (flows, pressures, etc…) only, but the next version will support integrating processes, too. It now supports both first order plus dead time and integrating processes. Once I implement integrating processes and a couple other features, an offline version will be available for a nominal fee. You can find out how to use PID Loop Analyzer in its documentation, About PID Loop Analyzer. I provide links to both in the left sidebar.
Try it out with the following data files. Note the lower range value, upper range value, and column assignments at the top of each file.