On-Line Trial and Error

To tune a controller on line, a good instrument mechanic follows a procedure something like the following  

With the controller on manual, take all the integral and derivative action out of the controller, i.e., set tj at maximum minutes per repeat and minimum minutes. 

Make a small setpoint or load change and observe the response of the con trolled variable. The gain is low so the response will be sluggish, 

Reduce the PB by a factor of 2 (double the gain) and make another small change in setpoint or load, 

Now start bringing in integral action by reducing by factors of 2, making small disturbances at each value of i to see the eifect. 

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