Performing Order Analysis in LabVIEW with Sound and Vibration Software

^{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.

The Sound and Vibration Measurement Suite includes easy-to-use Example VIs for the most common applications including:

• Analog Tachometer Signal Processing
• Order Power Spectrum
• Spectral Map Analysis for Waterfall and Colormap Plots
• Order Tracking - Magnitude and Phase
• Order Waveform Extraction

The following VI is an example that uses the Sound and Vibration Measurement Suite. This VI demonstrates how to compute an order power spectrum with averaging. This VI uses DAQmx VIs to acquire sound or vibration signals and an analog tachometer signal and displays the order power spectrum continuously.

Instructions for running this VI:

1. On the DAQ Configurations page on the front panel, specify the device and channel configurations, time settings, and tachometer channel information. 
2. On the Order Power Spectrum page on the front panel, specify the window type, block size or order resolution, and averaging parameters for power in band computation.  
3. Run the VI.

Also see Sound and Vibration Software Overview and Feature Comparison to learn more about which Sound and Vibration distribution meets your needs.

• Tachometer Processing
• Order Power Spectrum
• Order Tracking
• Order Extraction
• Angular Resampling
• Waterfall Plot
• Orbit & Shaft Centerline Plot
• Polar & Bode Plots
• Envelope Detection

• Patented Order-Tracking Algorithm
• Four Practical Applications of Joint Time-Frequency Analysis
• LabVIEW for Measurement and Data Analysis

• Sound and Vibration Measurement Suite and Pricing