Figure 1: Frequency-Time and RPM-Order Data Plotted Using NI Sound and Vibration in LabVIEW
Order analysis is a powerful tool used to study, design and monitor rotating or reciprocating machinery for which the rotational speed might change over time. As with frequency-domain analysis, you can think of order analysis as a signal scalpel that can dissect sound, vibration, and other dynamic signals into components that relate to physical elements of mechanical systems. From this, you gain a better understanding of the system and can identify characteristics that change with time and operating conditions. Unlike the power spectrum and other frequency-domain analysis standards, order analysis works even when the signal source undergoes rotational speed variations or frequency/Doppler shifts.
The Order Analysis VIs included in the Sound and Vibration Measurement Suite present the capability to calculate and examine rotational speed and extract the order components from the original noise or vibration signal. Power distribution can be measured as a function of either time or rotational speed and measuring the phase and magnitude of any order component as a function of rotational speed is made easy. Data is displayed in waterfall, orbit, polar, or bode plots.
In addition to several advanced VIs that provide flexibility and increased control of the analysis process, this toolkit also includes a set of Express VIs which allow you to perform simple without much programming. The toolkit also comes with extensive examples which demonstrate fundamental order analysis tasks such as data acquisition, data presentation, Gabor order tracking, and resample order tracking for both analog and digital tachometer signal processing. By leveraging these examples, you can develop applications much quicker.
You can apply order analysis to dynamic signals generated by mechanical systems that include rotating or reciprocating components, such as turbines, compressors, pumps, and engines. It is common to use order analysis in applications such as machine condition monitoring (MCM) and noise, vibration, and harshness (NVH) testing. With the added capability for online processing, you can easily create flexible applications for condition-based monitoring and predictive maintenance. The National Instruments NI Dynamic Signal Acquisition devices are ideal for acquiring sound and vibration signals with 24-bit A/D converters and anti-aliasing filters.