Tuning and Operating, Chapter 5
WATLOW Series 965 User's Manual
21
Chapter 5
How to Tune and Operate
Auto-tuning (Heat and/or Cool)
The Series 965 can automatically tune the PID parameters to fit the character-
istics of your particular thermal system.
The auto-tuning procedure operates on a thermal response value — slow,
medium, or fast. Use the slow thermal response when your process does not
need to reach set point too rapidly, or if it usually does not often exceed set
point. A fast thermal response produces a rapid temperature change over a
short period of time.
Once the auto-tune sequence has begun, the Output 1 heat proportional band
is set to 0 and the control goes into an on/off mode of control at 90% of the
established set point. The displayed set point remains unchanged.
Once the control finishes "learning" the system, it returns to a standard PID
control with the PID values automatically set as a result of auto-tuning. See
Manual Tuning on the next page to set the cool PID parameters. Any change
of the set point, while in auto-tune, re-initiates the auto-tune procedure.
Tuning
NOTE:
Set the HSC parame-
ter under the Setup
Menu to 3
°F/2°C
before auto-tuning
your control.
Figure 25 -
Auto-tuning at a
Set Point of 200
°F.
In order for the 965 to successfully complete auto-tune, the process must cross
90% of set point four times within 80 minutes after auto-tune has started. If this
does not happen within the 80 minute time limit, the Pb remains at 0 and the
control functions in an on/off mode.
200
°Temp
Set Point
100
Process
180
Auto-tune
Begins
Auto-tune
Complete
90% of
Set Point
Auto-tuning at a Set Point of 200°F
°Time
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