Sensor validation:principles and standards

It is widely recognised that internal diagnostics from the industrial sensor (here taken to mean both transducer and transmitter considered as a single unit) will improve the quality of plant control and maintenance. It is less obvious how to present diagnostic information in a standard format for integration into automated systems. Possibly the most comprehensive attempt to define a framework for diagnostic information is the SEVA (SEnsor VAlidation) scheme developed at Oxford University in the 1990s.However,although SEVA has been adopted as a British Standard (BS-7986) it has yet to be widely used within industry.A new SEVA Special Interest Group is being formed to extend its use in industry.In this article the principles behind the SEVA scheme is presented.This provides the basis for an analysis of other approaches to sensor validation,in particular the recent NAMUR document NE107 “Self monitoring and diagnosis of field devices”.