Watlow Series D8 - Manual (Page 110)

Chapter 4: Operation and Setup Series D8 User’s Guide
92 Watlow Anafaze Doc. 0600-3120-2000
and there must be sufficient time for the controller to deter-
mine the new PID parameters.
Prerequisites
Before autotuning, the controller must be installed with con-
trol and sensor circuitry and the thermal load in place. It must
be safe to operate the thermal system, and the approximate de-
sired operating temperature (set point) must be known.
The technician or engineer performing the autotune should
know how to use the controller keypad or HMI software inter-
face to do the following:
•
Select a loop.
• Change the set point.
• Change the control mode (manual, automatic, off or
tune).
• Read and change the setup parameters.
How to Autotune a Loop
NOTE! The loop must be stable at a temperature well
below the set point in order to successfully
autotune. The controller will not complete
tuning if the temperature exceeds 80 percent
of set point before the new parameters are
found.
To autotune a loop:
1. Go to the loop display (see Loop Display on page 80) and
press p to choose the loop to autotune.
2. Verify that process is stable.
3. Put the loop into manual control mode (see page 85).
4. Enter a set point value as near the normal operating tem-
perature as is safe for the system (see page 84).
WARNING! During autotuning, the controller sets the
output to 100 percent until the process vari-
able rises to 80 percent of set point. Enter a
set point that is within the safe operating lim-
its of your system.