a method of temperature control for maintaining actual temperature at a set point uses a learning period from which to acquire parameters that are used to control temperature . the method defines a learning period as one complete oscillation of the actual temperature about the set temperature . during such an oscillation period , the actual temperature will have been exclusively above and below the set temperature for one segment each . the invention provides a method for adjusting a variable in order to maintain a process measurement at a predetermined constant value , the method defining a sample period , wherein the sample period is a period of time represented by a complete oscillation of the process measurement about the predetermined constant value and wherein the complete oscillation includes a first time period during which the adaptable measurement is continuously above the predetermined constant value and a second time period during which the adaptable measurement is continuously below the predetermined value and wherein the first time period and second time period occur substantially sequentially .