This paper presents the generic model of intelligent

instruments and specifies it for intelligent sensors, from a functional

point of view, i.e., from the point of view of the services they

offer to the system designer. Basic services are concerned with data

estimation and data characterization, both based on local transducers

and on the availability of remote signals. Advanced services

are concerned with data validation, through fault detection and isolation procedures, and with fault tolerance, by means of accommodation

and reconfiguration strategies. Finally, the integration of intelligent sensors in distributed control systems is discussed.