Great way to explain PID Control Loop

[airman00]

From wikipedia

A familiar example of a control loop is the action taken to keep one's shower water at the ideal temperature, which typically involves the mixing of two process streams, cold and hot water. The person feels the water to estimate its temperature. Based on this measurement they perform a control action: use the cold water tap to adjust the process. The person would repeat this input-output control loop, adjusting the hot water flow until the process temperature stabilized at the desired value.

[guru]

Thats a good explaination of closed-loop systems, of which PID is an example. But it's not really a good explaination of PID specifically. I don't integrate or derivate each time I run my shower!

[guru]

Btw: another good example of a closed loop systems which we all understand is cruise control in our cars. The odometer is the measuring device, an actuator pulls the gas pedal down, and we set the desired speed with a button.

[arixrobotics]

One of the easiest to understand and then implement PID control tute that I've found is on the Lets Make Robots site;
http://letsmakerobots.com/node/865

[piercent]

Fluke just published a paper on troubleshooting automation and process control loops http://www.newark.com/images/en_US/marketing/pdf/ondemand092011/TroubleshootLoops.pdf.  It covers speed issues, tracing problems, checking i/o cards, malfunctions, calibration and more.  Also, here is the main process control page which may be helpful.