  This paper deals with sensors which compute and report linguistic assessments
of their values.Such sensors, called symbolic sensors are a natural extension
of smart ones when working with control systems which use artificial
intelligence based technics. After having recalled the smart sensor concepts,
this paper introduces the symbolic sensor ones. Links between the physical
world and the symbolic one are described. It is then shown how Zadeh's
approximate reasoning theory provides a smart way to implement symbolic
sensors. Finally, since the symbolic sensor is a general component, a
functional adaptation to the measurement context is proposed.
