Remote sensors with self-test: New opportunities to improve the performance of physical transducers

Men addressing the question on how to operate sensors in a remote environme nt, i.e., in non-accessible places, the issue of reliability becomes of ext reme importance. Especially in the case where miniaturisation is essential, often the physical geometries become that small that the sensor performanc e degrades to yield only very weak signal levels. Matching circuits are an essential element. Monitoring physical quantities from a remote and difficu lt to access location requires high standards for the sensors and their cir cuits involved: it is essential that the data remains reliable at all times . This is a hard requirement, and many sensors used in such applications ca nnot cope with such severe specifications, as there are: low drift, high st ability in time, immunity to cross sensitivies, etc. This paper focuses on a double solution: first by adding circuitry improving the intelligence of the entire sensor system. Secondly, it is shown how the sensor design in it self can be modified to improve the interface circuit performance. An essen tial element is the addition of built-in self-test features to verify the c orrect operation of the sensor at any given moment in time. Crucial in thes e novel developments is that the measurand itself is used to verify the ope ration of the sensor, and not a related actuation as is done in many existi ng devices.