Watlow PM PLUS 6 - Chapter 8: Features; Autotune

Watlow PM PLUS™ 6 • 77 • Chapter 8: Features
Chapter 8: Features
Autotune
When an autotune is performed on the PM PLUS™ the set point is used to calculate the tuning set point.
For example, if the active set point is 200° and Autotune Set Point is 90 percent, the autotune function uses
180° for tuning.
Autotuning calculates the optimum heating and/or cooling PID parameter settings based on the system's
response. The PID settings generated by the autotune will be used until the autotune feature is rerun, the
PID values are manually adjusted or TRU-TUNE+
is enabled.
Start Autotune
1. Navigate to: Operations
2. Scroll to select Yes .
3. Use the slider or +/- keys to set the set point for the tune.
4. Press the Home icon to return to the Home Screen.
Manual Tuning
In some applications, the autotune process may not provide PID parameters for the process characteristics
you desire. If that is the case, you may want to tune the controller manually.
1. Apply power to the controller and use the numeric slider or the +/- keys to select a set point for your
process.
2. Navigate to Operations — Setup - Control Loop , then scroll to and select Heat Proportional Band Heat
Prop. Band
and/or Cool Proporational Band Cool Prop. Band , then use the numeric slider or +/- keys to
change the value to
25 .
3. Press the Left Back Arrow to return to the Control Loop List, then scroll to and select Time Integral , then
use the numeric slider or +/- keys to change the time integral to
0 .
4. Press the Left Back Arrow to return to the Control Loop List, then scroll to and select Time Derivative , then
use the numeric slider or +/- keys to change the time derivative to
0 .
5. When the system stabilizes, watch the process value. If it fluctuates, double the Heat Proportional Band or
Cool Proportional Band value until it stabilizes, allowing time for the system to settle between adjustments.
6. When the process has stabilized, open Operations — Monitor and watch Heat Power or Cool Power. It
should be stable ±2%. At this point, the process temperature should also be stable, but it will have stabi-
lized before reaching the set point.
7. The difference between the set point and actual process value can be eliminated with Integral.
WARNING!
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During autotuning, the controller sets the output to 100 percent and attempts to drive the Process Value toward the
set point. Enter a set point and heat and cool power limits that are within the safe operating limits of your system.