Red Lion TSC - Manual (Page 71)

AUTO-TUNE
Auto-Tune is a user initiated function in which the
controller automatically determines the optimum
PID settings based upon the process characteristics.
The desired temperature setpoint should be entered
first. Auto-Tune may then be initiated at start-up,
from setpoint, or at any other process temperature
point. Auto-Tune may be invoked while a profile is
running and after Auto-Tune is complete, the profile
resumes operation.
After Auto-Tune is complete, the PID settings
remain constant until user modified. As shown in the
Auto-Tune Operation figure, Auto-Tune cycles the
process at a control point 3/4 of the distance between
the current process temperature where Auto-Tune
was initiated and the temperature setpoint. The 3/4
control point was selected to reduce the chance of
temperature overshoot at setpoint when
Auto-Tuning at start-up. If Auto-Tuning from
setpoint and temperature overshoot is unacceptable,
place the controller in the user (manual) mode and
reduce the power to lower the process temperature.
Allow the temperature to stabilize and execute
Auto-Tune from the lower temperature. After
starting Auto-Tune, the secondary display indicates
the current phase (Aut1, Aut2, Aut3, Aut4, & Aut5).
If the controller remains in an Auto-Tune phase
unusually long, the process or connections may be faulty. Auto-Tune may be
terminated at any time without disturbing the previous PID constants. As an
alternative to auto-tuning, the manual tuning procedure can be used to give
satisfactory results.
Prior to initiating Auto-Tune, it is essential that the controller be configured
to the application. In particular, control hysteresis (CHYS) and Auto-Tune
damping code (tcod) must be set in the Output Parameters section. Generally,
control hysteresis of 2 - 5 degrees is adequate. The damping code may be set to
yield the response characteristics shown in the damping code figure.
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AUTO-TUNE OPERATION FIGURE