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irrespective of any accelerometer placement is defined as shown in Figure 3-9 and Figure 3-10. All accelerometers are attached using wax.


                (a) blower                                 (b) pump
Figure 3-9 Accelerometers mounted at possible vibration sources, i.e. at the (a) blower and the (b) pump respectively.


Figure 3-10 Accelerometer mounted approximately at the midpoint of the test section to detect vibration levels. Flow direction is along X. A signal conditioner is used prior to acquiring the data from the accelerometers. A HUP E1433 16 channel 52 k~lz digitizer is used for acquiring the data. Each channel has a built-in programmable anti-aliasing filter whose cutoff span, fi, is determined by the sampling frequencyjf, as


                                        f~/2.5 6                                 (3.1)