I wrote this booklet in the middle 80’s when pneumatic controls ruled in the HVAC Industry and DDC was just beginning to appear. (We were all fascinated with what can be done with a microprocessor based control with 16k bytes of memory!) Although the content is a little dated, I still think it should serve very useful for people trying to figure out just what a PID controller does and how it is different from a straight Proportional only controller.
I will post this booklet in 3 parts: Part-1 Introduction and Proportional. Part-2 Integral. Part-3 Derivative.
I hope you find it useful. Please click on the PDF link below and then come back here for your comments.