Module 4 PID Demonstration

Go to the following website in order to complete this activity. It will open a Liquid Flow Rate Controller interactive demo that you will use throughout this activity.

(It may be useful for you to print out these instructions so that you can fill in your responses to the questions and bring them to class)

http://dexautomation.com/pidtutorial.php

Control Loop

Notice the following elements once the page is displayed:

LEAVE PUMP OFF FOR NOW

Proportional Demo

Instructions:

  1. Put controller in AUTOMATIC by clicking A/M button
  2. P is set for 100%
  3. Raising SP has the same effect as on the controller as a falling PV
  4. Try it changing SP to 0 and then 10
  5. Change SP to 20, then 40
    Describe what happens and be prepared to share your answer with with the class:

  1. Set SP to 0
  2. Set P to 50
  3. Change SP to 10. Does output change by 20%? A change of 10 causes a change of 20 or a gain of 2
  4. Put controller back to MANUAL.
  5. Set P to 100
  6. Set OP to 100%
  7. Start pump by clicking START
  8. Put controller back to AUTOMATIC
  9. Change SP to 20
    Does OP change from 100 to 80?

  1. Then decrease P by small amounts and note change in PV.
    Describe what happens if P is set too low and be prepared to share your answer with the class:

  1. Set P to 50 and change SP by small amounts
  2. Set P to 100 or put pump back to MANUAL before it blows the seals!!!!!

Integral Demo

Instructions

  1. SP to 0, OP set to 100, I set to 0, and D set to 0. Pump is OFF.
  2. Put controller in AUTOMATIC
  3. Change SP to 10.OP should change from 100 to 90
  4. Change SP back to 0
  5. Change I from 100 to 90. Note that I takes over and move OP from 90 to 80 for next minute. Make sure the controller is working by verifying the OP is changing every 1 minute.
  6. Put controller in MANUAL
  7. Then put controller in manual and set OP to 100
  8. Set I to 2
  9. Put controller back to AUTOMATIC.
    Describe what happens and be prepared to share your answer with the class:

  1. Repeat the previous steps using the following :
  2. Once familiar with how P and I interact, Start pump and try tuning the controller.
  3. Start with P set to 100 and I set to 0.
    Describe your results and be prepared to share your answer with the class:

Derivative Demo

Instructions

  1. Put controller in AUTOMATIC
  2. Click BLUE button up on signal generator to cause controller input to slowly ramp up.
  3. Note how green and white lines mirror each other. This is the result of the P’s corrective action.
  4. Click STOP on signal generator. This stops the ramping action.
  5. Change controller back to 200 degrees by typing 200 into signal generator window and press “ENTER”
  6. Change D to 0.5
  7. Click up arrow on generator
    Note what happens and be prepared to share you answer with the class (derivative action is a proportional to the rate of change of the process. It is designed to stop the PV from changing and then its job is done):

  1. Click stop on the signal generator.
    Note what happens and be prepared to share you answer with the class:

  1. Experiment with different values for P and D.
    Note what happens and be prepared to share you answer with the class:

Critical thinking Activity

Create a small processing lab. Create a lab that would use the PID to control this process.