Proportional Integral Derivative Controllers One of the biggest control discussions in the coffee industry lately has
revolved around proportional integral derivative (PID) controllers: logicbased controllers that allow the user to input temperature set points, and influence the logic. The PID’s ability to control heating functions is well known but not well understood by most coffee professionals. Happily, roasters and baristas alike are trying to figure out how to use these tools to better control their respective processes. Most new coffee roasters delivered today have at least a simple PID controller installed as standard equipment, and many come with fairly sophisticated PID profiling controllers. Most roaster operators, however, have no clue as to what PID stands for or, more importantly, how to use this technology to their benefit.
Those who don’t understand the technology may use their PID controllers for set point controlling, or simply as digital temperature readers. When roasters use a PID as a set point controller, they input a set point in their controller and allow the bean or air temperature to rise to that point at which time the controller either sounds an alarm, shuts off gas to the burner or both. Although this can work very well and is a great improvement in controllability, repeatability and safety from the stopwatch and trier systems of the past, it is in fact an underutilization of a PID controller. A properly set PID controller, with a controllable gas train, can help make coffee roasting a much more exact and repeatable process, thereby freeing the roaster to work on other elements of quality control (namely green coffee and blending) that are so essential in
the creation and sustainability of great coffee.