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**OPTIMUM
PID CALCULATION**

based on Cohen-Coon's tuning
rule

1. Draw a tangent line at
the steepest point of an open loop response curve

2. Estimate the dead time,
Td.

3. Estimate the time constant,
Tc, as shown in the figure above.

4. Calculate the uncontrolability
parameter as defined below.

5. Select the controller
mode i.e. P only, PI or PID

6. Calculate the PIDs based
on the following:

**For
P only control**

**For
PI control**

**For
PID control**

Note: RR is the process rate
per controller output as defined in "Optimum
PID calculation for SR and NSR process".

16 October
99 / updated: 15 Aug. 2001