Sensors are used to gain information about the world that is useful for guiding a robot to achieve a particular goal. Typically, the values returned by sensors have to be interpreted in order for the information to be directly useful for control purposes.
Interpretation involves mapping sensed values to states of the world.
Noise can come from sources in the external world, e.g., ambient light sources when you're trying to measure light from a particular source, or from the sensors themselves or any part of the sensor processing, e.g., degradation in the electrical characteristics of a sensor. In building good sensor systems, we'll have to understand the underlying physics as well as what we intend to use the information for in building a control system. In Wednesday's lab you'll learn more about using the sensors in your robot kit, but today we'll talk about a much wider range of sensors, their limitations and applications in which they have been found to be particularly effective. As one source of additional information, Dave Gasperi has written extensively about the Lego sensors and his web page includes some information on the Lego light sensor drawn from a number of sources including a Japanese fellow who has reverse engineered the Lego light sensor. Gasperi discusses various methods for overcoming the limitations of having only three sensors , including ORing and ANDing sensor inputs together.