Control Algorithm, continued
How control algorithms are characterized
Control algorithms are characterized by plotting the output as a function of the input under open-loop conditions, that is, when no feedback is present. The figure below shows plots of the open-loop response functions
for the three basic control algorithms.
The y-axis is the output control voltage (typically the 0- to 10- Volt signal to the dimming ballast). The x-axis is the optical signal received by the photosensor. Loosely speaking, this optical signal can be thought
of as the illuminance on the photosensor, but the distinction between sensor signal and sensor illuminance is important because a photosensor does not necessarily respond to illuminance. In fact, most photosensors have response characteristics quite different from an illuminance meter (see sections on spectral and spatial responses).