Watlow MLS - Manual (Page 70)

58 MLS User’s Guide
Using the MLS
Automatically Tuning a Loop
When you use the Autotune function, the controller automatically sets
the loop to Manual control, 100% output. (If you selected a continuous
output limit, the controller sets the loop to the output limit.) The
autotune function calculates the appropriate PID constants for the loop
and puts the loop in automatic control with the calculated PID values.
The Autotune function will abort if:
• The process variable goes over 75% of the setpoint. (Remember, the
controller is at 100% output or at the output limit you set.)
• The controller has not calculated PID constants after 10 minutes (due
to heater failure, sensor failure, etc.).
If the autotune function aborts, it puts the loop into its previous control
state (Automatic or Manual control) at the previous output percentages.
To automatically tune a loop, follow these steps:
1. Make sure the process is cold (or stable and well below setpoint).
2. Initiate Autotune:
1. Use the front panel keypad to go to Single Loop Display.
2. Press the Man/Auto key.
3. Choose Tune.
4. Press Enter.
The Tune indicator will flash and the controller will return to Single
Loop Display. The Tune indicator will flash as long as the loop is
tuning.