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Publisher Summary This chapter presents the example of fault detection systems. An example is the optical sensor network system, which is characterized by the use of an optical-fiber network connecting optically the devices in the field with the central computer system. In this system, the detection operations themselves are performed directly by means of optical methods or the electric signals from the usual sensors are changed into optical signals in a sensor-interface processor. The other example is the group of new sensors for the detection of faults. These sensors are based on various optical principles. The technical fields required in the development of fault detection systems are divided into two groups: (1) the abnormality and its type and degree are derived from the signals from the usual sensors, which are not specially developed, and (2) on the other hand, the real difficulties arising in fault detection systems, in many cases, have been caused by the difficulties of access for the usual sensors because of physical hazards or narrow spaces, or by the inadequacies of the sensors themselves with respect to the detection of physical data from the faults. In the chapter, an optical-fiber network system and the optical apparatuses used in the network, which are useful for construction of intrinsically safe systems, and optical sensors developed specially for difficult inspection targets have been presented. The optical techniques may be useful for the further development of sensing systems in this field. |
