Ziegler-Nichols Loop Tuning
The Ziegler-Nichols loop tuning protocol1) is a simple method to establishing the loop parameter values for a PI or PID control loop. This protocol is designed to optimize the loop for disturbance rejection.
Links
Instructions
| There is the possibility for the loop to go unstable at too high gain. Use caution as gain is increased. |
From the Home Screen, touch the Channel icon for the loop to be tuned
Touch Settings > PID Params
Choose a Set Point temperature
Set Proportional Gain (KP) to 0
Turn off Integral and Differential portions of the loop (TI & TD, respectively)
While monitoring the error in temperature on rolling graph on the SLICE-QTC display or an
external oscilloscope,
slowly increase (~10% per increment) K
P until the error begins to oscillate
Use the

and

icons, to scale displayed response appropriately
Use the

icon to pause the graph
Note: the pause icon only pauses the graph, not the servo control
Note KP where oscillations of increasing amplitude begin; this is KP, cr, the critical proportional gain.
Use the Cursors enabled by touching the

icon to measure the period of oscillation, T
cr
You can use the two rotary knobs or touch & drag the cursors on the touch screen
Use the following table to set the values of KP, TI, and TD
Type of Control Loop | KP | TI | TD |
PI | 0.45•KP, cr | 0.83•Tcr | 0 |
PID | 0.6•KP, cr | 0.5•Tcr | 0.125•Tcr |
Tab. 1: Ziegler-Nichols loop values