For the automatic monitoring of machine components a system, consisting of a glass fibre based interferometer and a computer for the digital signal analysis, will be described. The interferometer is entirely composed of glass fibre components, starting with a diode laser, internal glass fibre components and a detector head. This set-up, which is very flexible, results in an almost adjustment and maintenance free optical system. Since it is a contact-free monitoring system, moving components such as rotating shafts can be supervised. The heterodyne laser interferometer detects vibrations in a broad spectrum from DC to 20 MHz. The first signal coming from the interferometer will be digitised and further processed with digital signal analysis methods. In particular, the first signal is demodulated and the spectrum is analysed. The basis of the spectrum analysis is the calculation of characteristical numbers and their graphical display. Changes within the characteristical numbers lead to the conclusion that the vibration pattern of the supervised machine has changed. These changes may be caused by uncritical different operating modes, as well as developing material defects. After the software has been calibrated for each application, such changes can be automatically detected, correctly interpreted and the appropriate information will be displayed. The operator will be informed either about the correct machine operation, displayed in green colour, or about a material defect, displayed in red.
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