Super-conducting sensor

Citation

(2003), "Super-conducting sensor", Sensor Review, Vol. 23 No. 1. https://doi.org/10.1108/sr.2003.08723aab.003

Super-conducting sensor

Super-conducting sensor

Keywords: Metals, Fatigue, Super conductors, Sensors

A new super-conducting sensor has been jointly developed by Japan’s Seiko Instruments Inc. and its Shimizu Corp. It is used to pinpoint metal fatigue in steel structures such as bridges and aircraft before cracks actually appear. The various types of nondestructive tests already available detect the actual cracks once they have been formed. The sensor, which is based on a super-conducting quantum-interference device that exploits the zero resistance of super-conducting materials, to detect even very faint magnetic fields, is placed some 6 mm above the steel sample, and scanned across the surface while taking readings every 1 mm. These readings are used to create a magnetic contour map that shows the distribution of changes in the magnetic properties of the inside of the material.

Steel has an orderly composition in which the magnetism of neighboring regions normally cancel each other out, so that only a weak magnetism is detected. However, the strength of the magnetism increases where the steel is strained, and it is these places that show up on the map.

Nevertheless, there are drawbacks with the system, one being that the system uses a niobium-type super conductor that must be cooled to −269°C to achieve its super-conducting state. Seiko and Shimizu are considering to design a similar sensor that will be based on a high-temperature super conductor but in the meantime they are continuing the development of the existing sensor.