In all the tests, vibration accelerometers were mounted in four different locations, to record radial and axial vibration signals as shown in Fig. 1.2. Two pick-ups with magnetic bases were mounted radially, one on the outer race and the other on the end shield. In addition, one pick-up with a magnetic base was mounted axially on the end shield, while one pick-up with a stud base was mounted radially on the end shield to assess the attenuation of the signal. The signals from the different pick-ups were recorded on the four-channel B&K tape recorder in acceleration mode, to carry out further detailed analysis of the signatures by using a real-time analyser in the laboratory.
A number of resonances can be detected by an accelerometer mounted on the bearing surface. The signal from accelerometer, after some amplification, is tape recorded for high-frequency resonance analysis at a later time. When setting up such an analysis system, the output signal from the accelerometer is directly analysed in the real-time frequency spectrum analyser. This step helps in determining the carrier (resonant) frequencies, which are being most strongly modulated by the defect frequencies. The accelerometer signals are then envelope-detected about these frequencies in order to determine which of them is the best carrier for the particular defect frequency.
The system comprises an input amplifier, a multiplier,...
TABLE OF CONTENTS 
