Red Lion PCU - Manual (Page 85)

CLOSED LOOP CYCLING METHOD
An alternative to auto-tuning is manual tuning. This tuning method induces
oscillations into the process in the same way as the controller’s auto-tune
function. If oscillations are not acceptable, the open-loop tuning method can
be used.
The following is a manual tuning procedure for determination of the PID
control constants.
1. Connect a chart recorder to log process value and set the paper speed
appropriate for the process.
2. Set the controller to automatic (auto) control mode.
3. Set proportional band to 999.9%. (maximum setting)
4. Set integral time and derivative time to 0 seconds.
5. Decrease proportional band (increase controller gain) by factors of two
until process just begins to oscillate and the oscillations are sustained.
Make a small change in setpoint to provide a stimulus for oscillations.
Allow adequate time for the process to respond. If oscillations appear to
grow, increase proportional band. Adjust the proportional band until
steady oscillations appear.
6. Note the peak-to-peak amplitude of the cycle (a) in degrees and the period
of oscillation (t) in seconds.
Parameter Fast Response
Damped
Response
Slow
Response
Proportional Band (%) 200a/range 400a/range 600a/range
Integral Time (sec) 1t 2t 3t
Derivative Time (sec) 0.2t 0.25t 0.25t
Output Power
Dampening (sec)
t/40 t/30 t/20
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Figure 42, Closed Loop Tuning