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Vibration Fundamentals Episode 10

Tham khảo tài liệu 'vibration fundamentals episode 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 264 Vibration Fundamentals D-Mag Spec-Al Figure 28.7 Standard free-run spectrum analysis performed with 1000 spectrum averages. Figure 28.8 Sync averaged spectrum of same signal shown in Figure 28.7. takes place theoretically the cleaner the signal gets until the only signal left is the trigger or synchronizing frequency and its harmonics. The spectrum shown in Figure 28.7 is the result of 1000 averages of a free-running signal input. The only apparent signal is a peak at 40 Hz. However it is suspected that there might be a signal contributing at approximately 37 times the nominal 40-Hz component. To verify this a synchronous time average was performed with a reference signal of 1466 Hz. The time synchronous spectrum shown in Figure 28.8 was performed with 3400 time averages followed by a single FFT. This technique makes it apparent that a clear signal exists at 1466 Hz. Also note that the amplitude of this 1466 Hz component is less than half that of the amplitude of the 1466 Hz component in Figure 28.7. This indicates that the desired signal is at least 6 dB below the level of the surrounding noise in the original broadband spectrum. Chapter 29 ZOOM ANALYSIS Zoom analysis provides the means to separate quickly machine-train components such as gear sets from a complex vibration signature. The technique lets the user select a specific range of vibration frequencies which the real-time analyzer converts to a high-resolution narrowband signature. This capability is unique to real-time analyzers and is not available in general-purpose single-channel vibration analyzers. Real-time zoom analysis can be performed with no data gaps up to a range of 10 kHz with most microprocessor-based real-time analyzers. However the center frequency plus one-half of the selected frequency span cannot exceed 10 kHz. Above this range pseudo-real-time processing occurs which means that data required to perform the zoom transform are acquired until the extended recorded memory of the .