Note that many analog controllers used reset settings in repeats per minute instead of reset time for the integral mode tuning setting. Repeats per minute indicate the number of repeats of the proportional mode contribution in a minute. Today’s reset time settings are minutes per repeat or seconds per repeat which gives the time to repeat the proportional mode contribution. Often the “per repeat” term is dropped giving a reset time setting in minutes or seconds.
Seconds per repeat = 60 / repeats per minute
Integral Mode Advantages
• Eliminate offset
• Minimize integrated error
• Smooth movement of output
• Integral Mode Disadvantages
• Limit cycles
• Overshoot
• Runaway of open loop unstable reactors