Tuning Assistant

The Tuning Assistant menu option will allow the user to automatically generate the PID loop settings for the temperature control loops in the 9125 controller.  Select the loop to tune and click on the Edit button to auto tune that loop.

 

Note: The four buttons at the bottom of the screen: Use  UD (Under Damped), Use  CD (Critically Damped), Use  OD (Over Damped), and Use PI will be inaccessible until some PID settings are loaded into the PID settings list above the buttons.  The Return button in the bottom right of the screen will display the previous screen.

 

The “Conservative” option will allow the user to minimize, if not remove, the possibility for an overshoot of the setpoint.  If a small overshoot is acceptable, leave the “Conservative” checkbox unchecked.  If, however, no overshoot is desired, then checking the “Conservative” checkbox will accomplish this.

 

The “Max Output” checkbox allows you to set a maximum output percentage; this feature is useful when output may need to be limited due to physical characteristics of the furnace.

 

The current PV value, along with the setpoint, is listed above the PID settings list.

 

Pressing the Start button will begin the auto tune process.  Note:  The process may take a few seconds to start.  The “Idle” line will change to display the process for the auto tune.  The line will display a pointer value. 

 

Note: The Start button will be disabled while the tuning is running.  Pressing the Abort button will abort the process.  If the Cancel button is pressed while a tuning is running, a message box will be displayed confirming the action.

 

During the tuning, the temperature will oscillate around the setpoint 3 times before Tuning Assistant suggests tuning parameters. Depending on the heating and cooling abilities of the equipment, this can take a few minutes up to a few hours.

 

When the tuning is finished, the PID settings list will be populated with suggested values and the four buttons underneath will be enabled.  The line above the PID settings list will read “Idle” again as well.

 

The user has the option to select only one of these sets of values: either the Under Damped set, the Critically Damped set, the Over Damped set, or the PI set.  To select the set of values, press the corresponding button.  For example, to select the Critically Damped set of values, press the Use CD button.

 

The under damped values will reach the setpoint faster, but there will be more overshoot involved. 

The over damped values will work to minimize the overshoot, but it will be slower than the under damped values. 

 

The critically damped values provide a balance between the underdamped and overdamped values with regard to time and overshoot. 

 

The PI values are the proportional band and the reset value (the P and the I from PID).

 

Once a set of values has been accepted, the user can press the Return button to exit the screen.  The accepted values can be viewed on the PID Loop Setup menu option.  In future tuning sessions, the most recent tuning parameters will be retained and adjusted PID sets will be offered.