Tempco TEC-2500, Instruction Manual

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The PBu is called the ultimate P band, and the period of oscillation Tu is called the ultimate period in the flow chart in
figure 3.23. When this occurs, the process is said to be in a critical steady state. figure 3.24 shows an example of a
critical steady state.
If the control performance using above tuning is still unsatisfactory, the following rules can be applied for further
adjustment of PID values:
figure 3.25 shows the effects of PID adjustment on process response.