That depends on incline, wind, and so on. It is this position on a scale of possible values that we seek to control. Although diverse uses of certain terminology probably preclude calling the variable a quantitative measurement, the concept of the variable representing a current location on a scale of possible values, a status quo, seems to hold up. Figure 1B illustrates how a change in controller output, dCO, when written as system input, is a change in the rate of a system input. Following an increase in the system input rate, however, the change in the variable, dV, could, as noted, continue indefinitely.
Applications exist where it is many times greater.
Figure 2 shows a plot of run data from an actual application with the Controller controlling the temperature of water in a beaker. Consider, as a thought model, a tank level control application where, initially, level, system input, and system output are constant. Note the initial values for the variable, V O , and the controller output, CO O . From these values, much can be discerned about the model's system and the process controller's relationship thereto, for example, Model . Using the above developed concepts and formulae, it is possible to simulate the dynamics of a system controlled by the Controller.