4. In order to tune an important PID control loop on a large unit operation, the plant engineer sets the controller to proportional mode only and then begins to collect data from the process. He makes a small adjustment in the controller set-point to 'bump' the process and then gradually increases the controller gain every three hours. The schedule of tests is shown in Table Q4 and a chart recorder view of the process output over the duration of the testing period is shown in Figure Q4. Table Q4 Test Schedule (a) What tuning method is the engineer using? (b) Estimate the value of the ultimate gain in this situation and explain the reasons for your choice. (c) Estimate the value of the ultimate period in this situation and explain how the value was calculated as accurately as possible. (d) Calculate appropriate controller settings for the PID controller. (e) Briefly discuss the practical issues that surround the use of this technique for tuning controllers in industrial situations