Getting Started with Order Analysis
Contents
1. speed profile p gt speed profile olormay colormap Speed profile GH ab Control h 4 i 1 Order Spectrum es gt input signal gt speed profile rder power spectrum spectrum _ Prad i Ej y gt gt e Order Tracking fo gt input signal a gt speed profile lagnitude magnitudes gt tei Figure 9 Creating the Magnitude Plot 8 Run the Getting Started Exercise VI to compute and display the magnitude of the seventh order of the computer fan run up data 9 Save this VI On the front panel click the Order Tracking tab to display the Magnitude plot for the seventh order of the computer fan run up data You can see that this order has greater amplitude around 2 600 RPM with a dip between 2 450 RPM and 2 650 RPM as shown in Figure 10 This dip is difficult to observe with the colormap alone National Instruments Corporation 13 Getting Started with Order Analysis Magnitude Magnitude g rms j ans 1 j 1 1 j j 1 1 1 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 Speed RPM Figure 10 Magnitude Plot of the Seventh Order You also can use the Order Tracking Express VI to compare the magnitudes of different orders For example if you add a second element to the Orders to track input and set the element to 8 the Magnitude plot displays the seventh and e2. H gt speed profile olormay i colormap i Speed profile Tab Control i ol H Order Spectrum gt input signal gt speed profile rder power spectrum spectrum _ Figure 6 Creating the Order Power Spectrum 9 Run the Getting Started Exercise VI to compute and display the order power spectrum of the computer fan run up data 10 Save this VI Getting Started with Order Analysis 10 ni com On the front panel click the Order Power Spectrum tab to display the Order power spectrum plot for the computer fan run up data as shown in Figure 7 Order power spectrum Power SSS See Teal 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Order Figure 7 Order Power Spectrum at 2 600 RPM The Order power spectrum plot displays the order amplitudes at 2 600 RPM Notice that the seventh order has the strongest amplitude on the plot The fourth order also is strong at 2 600 RPM The seventh and fourth orders correspond to the seven blades of the fan and four coils of the electric motor respectively Similarly as you observed with the RPM Order plot in the Spectral Map Express VI the seventh order loses amplitude at around 2 900 RPM and the eighth order gains amplitude around this rotational speed Complete the following steps to compute and display the order power spectrum of the computer fan run up data around 2 900 RPM 1 On the block diagram double click the Order Spectrum
3. National Instruments Corporation 9 Getting Started with Order Analysis Complete the following steps to compute and display the order power spectrum of the computer fan run up data at 2 600 RPM 1 On the Order Analysis Express Measurements palette select the Order Spectrum Express VI and place it on the block diagram A configuration dialog box appears On the Processing Settings page set the Processing mode to Delta Speed In the Limit range options set the Start speed RPM to 2600 and set the End speed RPM to 2600 On the Spectrum Settings page set Linear dB to Linear Click the OK button to save the current configuration and close the configuration dialog box Wire the waveform signal output of the oax_Load Data Analog Tacho single channel VI to the input signal input of the Order Spectrum Express VI Wire the speed profile output of the Analog Tacho Processing Express VI to the speed profile input of the Order Spectrum Express VI Wire the spectrum output of the Order Spectrum Express VI to the Order power spectrum indicator The block diagram should appear similar to Figure 6 loax_Load Data Analog Tacho single channel vi ard pease l Order ist 1 ea Analog Tacho y Processing q Spectral Map t analog tacho sign SS gt input signal speed profile p
4. Analog Tacho Processing amp analog tacho sign eed profile speed profile gt Tab Control Figure 2 Creating the Speed Profile 6 Run the Getting Started Exercise VI to calculate the rotational speed of the computer fan and to display the information in the Speed profile plot 7 Save this VI On the front panel the Waveform and Speed tab displays vibration signal and speed profile plots of the example data From the Input signal plot you can see that the vibration amplitude of the computer fan generally increases over 15 seconds The Speed profile plot shows that the rotational speed of the computer fan increases steadily from approximately 1 400 RPM to 3 700 RPM over 15 seconds The Input signal and Speed profile plots therefore illustrate that the vibration amplitude is approximately linearly related to the rotational speed of the computer fan Getting Started with Order Analysis 6 ni com Analyzing the Colormap A colormap is a three dimensional display of a sound or vibration spectrum as a function of time or speed The spectrum can be a frequency or order spectrum Use the Spectral Map Express VI to compute the spectral map of a sound or vibration signal This Express VI can return the spectral map in a colormap or a waterfall graph You can use this Express VI to create a colormap of the computer fan run up data Complete the following steps
5. 9 Analyzing the Magnitude Plot cee eeceeseeseeeteeeneeeneeeeaees 12 Extracting Order Waveforms ececeeeeseeseeseeeeeeeeeeeeseenes 15 SUMMATY serron ccs vane ds cunts xp eoviverbtvstoctesuss scedvevsssevevetenesiasavert sees bees 18 7 NATIONAL p INSTRUMENTS Introduction to Order Analysis Order analysis is a technique for measuring and analyzing sound and vibration signals generated by rotating or reciprocating machinery such as engines compressors turbines and pumps These machines have a variety of parts and each part contributes a unique sound and vibration pattern to the sound and vibration pattern of the whole machine With order analysis you can identify and isolate these sound and vibration patterns to analyze the performance and quality of each machine part individually The information you gather with order analysis often is difficult to acquire with traditional sound and vibration analysis methods Traditional sound and vibration analysis methods such as Fast Fourier Transform FFT analysis cannot detect mechanical characteristics that change with speed Order analysis on the other hand enables you to identify data at various orders or harmonics of the rotational speed The first order refers to the speed at which the machine rotates Each order thereafter is a corresponding multiple of the rotational speed The second order is twice the rotational speed and the third order is three times the rotational speed
6. Express VI to display the configuration dialog box 2 On the Processing Settings page of the configuration dialog box set the Start speed RPM to 2900 and set the End speed RPM to 2900 3 Click the OK button to save the current configuration and close the configuration dialog box 4 Run the Getting Started Exercise VI National Instruments Corporation 11 Getting Started with Order Analysis On the front panel you can see that the eighth order now has a much greater amplitude than the seventh order does as shown in Figure 8 Order power spectrum 0 016 0 014 0 012 0 01 Power 0 008 0 006 0 004 0 002 Spe Se SS ES ee See see re ero See 0O 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Order Figure 8 Order Power Spectrum at 2 900 RPM Again the fourth order also is significantly strong at around 2 900 RPM The eighth order and other order multiples of four correspond to the four coils of the electric motor of the computer fan An order power spectrum plot therefore provides detailed information about the strength of each order at a specific speed You also can use the Order Spectrum Express VI to compute the strength of each order at a specific time and to perform spectrum averaging Analyzing the Magnitude Plot A magnitude plot can help you analyze a sound or vibration signal by focusing on particular orders Use the Order Tracking
7. Getting Started Exercise VI to compute and display the colormap of the computer fan run up data Save this VI 7 Getting Started with Order Analysis On the front panel click the Colormap tab to view a colormap of the computer fan run up data as shown in Figure 4 Colormap 2E 3 1 8E 3 1 6E 3 apnyydwy 1 4E 3 1 2E 3 1E 3 Frequency 800 600 400 200 0 0 Figure 4 Frequency Time Plot By default this plot displays frequency against time Red portions of the colormap indicate areas of strong amplitudes Notice that several red lines appear on this colormap These red lines correspond to strong vibrations at different frequencies in the data Notice that the strongest vibrations occur at frequencies between 150 Hz and 400 Hz This range most likely includes several resonant frequencies from the DUT You also can customize a colormap to display RPM against order Complete the following steps to compute a colormap for the example data that displays RPM against order 1 On the block diagram double click the Spectral Map Express VI to display the configuration dialog box 2 On the Configuration page of the configuration dialog box change the Plot type to RPM Order An RPM Order plot displays how the vibration amplitude at different orders changes with the rotational speed From the Colormap plot in Figure 5 you can see that the amplitude of the seventh order is the strongest aro
8. analysis you perform can be in understanding the behavior of the system The DUT for the exercises in this section is a computer fan with four coils and seven blades The example data you use represents a 15 second run up test of the computer fan Run up and run down tests are useful for identifying orders that generate significant amplitude only when the DUT approaches or surpasses the critical speed or resonant frequency National Instruments Corporation 3 Getting Started with Order Analysis Analyzing the Example Data The Order Analysis Express Measurements VIs provide common analysis methods you can use to acquire information about the orders in a sound or vibration signal You can use these Express VIs to analyze the computer fan run up data In the following exercises you use the Getting Started Exercise Empty example VI as a template to build an order analysis application with the Order Analysis Express Measurements VIs You can access the Getting Started Exercise Empty example VI by selecting Help Find Examples from the pull down menu and selecting Toolkits and Modules Order Analysis Getting Started in the NI Example Finder window When you complete these exercises the block diagram of the Getting Started Exercise Empty example VI should appear similar to the block diagram of the Getting Started Exercise Completed example VI as shown in Figure 1 ao ray gt Analog Tacho Processing analog
9. and so on Using order analysis you therefore can analyze signal variations due to changes in speed Order Analysis Applications In general you can perform order analysis in the following types of applications e machine condition monitoring MCM e noise vibration and harshness NVH testing MCM applications typically analyze vibration response data to identify defective parts and ensure continuous performance NVH applications typically analyze sound and vibration data to verify the quality of a system and identify parts that produce unwanted sound or vibration Unlike MCM applications NVH applications generally analyze the sound and vibration of machine parts that function properly For example commercial airplane engineers might use NVH analysis to reduce cabin noise With NVH analysis the engineers can isolate and identify the source of the unwanted noise such as the aircraft engines The engineers then can redesign the rotating part of the engines and verify the improvement again using NVH analysis You can use the order analysis tools in the NI Sound and Vibration Measurement Suite to develop both MCM and NVH applications This document focuses on using these order analysis tools for NVH applications The Sound and Vibration Measurement Suite provides Order Getting Started with Order Analysis 2 ni com Analysis VIs and indicators with which you can develop a complete NVH application from the logging of online data to
10. data analysis and presentation Refer to the LabVIEW Help for more information about order analysis theory and applications Performing Order Analysis with Example Vis The Sound and Vibration Measurement Suite includes examples to help you get started with order analysis Select Help Find Examples in LabVIEW to launch the NI Example Finder Select Toolkits and Modules Order Analysis in the Browse tab to view all of the available examples or use the Search tab to locate a specific example You use an example VI that the Sound and Vibration Measurement Suite provides to perform the exercises in the Building an Order Analysis Application section Building an Order Analysis Application In this section you use the order analysis tools in the NI Sound and Vibration Measurement Suite to build a noise vibration and harshness NVH testing application You use these tools to perform offline order analysis on example data This example data represents the speed and vibration amplitude of a computer fan during a run up test The exercises in this section illustrate the common analysis methods you can use to acquire information about the orders in the data You can complete the exercises in this section in approximately 40 minutes Description of the Device under Test An effective order analysis application requires a thorough knowledge of the device under test DUT The more information you have about the DUT the more useful the
11. orders list press the lt Ctrl gt or lt Shift gt key to select the fourth seventh and eighth orders simultaneously Click the Export button to export the combined order waveform of the fourth seventh and eighth orders to the block diagram Clicking the Export button also adds the combination of the fourth seventh and eighth orders to the Output list Click the OK button to save the current configuration and close the dialog box 17 Getting Started with Order Analysis 10 Run the Getting Started Exercise VI 11 Save this VI On the front panel the Order waveform plot now displays both the waveform of the seventh order and the waveform of the combination of the fourth seventh and eighth orders as shown in Figure 14 Order waveform 0 6 0 4 0 2 Amplitude o I 0 2 0 4 0 6 0 8 1 1 1 1 1 1 1 i 0 2 4 6 8 10 12 14 16 Time s Figure 14 Comparing Order Waveforms You can add different order waveforms together in different combinations You then can play back the resulting waveforms as sounds and determine which combination is the most pleasing to the ear This way you can determine how to reduce the harshness of the signal and how to remove undesirable sounds and vibrations Summary You can use the Order Analysis Express Measurements VIs to perform most common types of order analysis You can use these VIs and the following plots to display data from different perspectives e V
12. tacho sign g speed profile gt F Spectral Map input signal speed profile olormap colormap gt ab Control ee gt Order Spectrum m gt input signal gt speed profile spectrum gt PLA gt E rerev a Order Tracking p input signal jeee speed profile magnitudes levels E Hececeelh bc Order Waveform gt input signal speed profile Prder waveform order waveform gt E Figure 1 Block Diagram of the Getting Started Exercise Completed Example VI The Getting Started Exercise Completed example VI uses the colormap order power spectrum magnitude and order waveform plots to analyze the sound and vibration data from the computer fan Each plot displays the Getting Started with Order Analysis 4 ni com same information from a different perspective You can use these plots to analyze the example data and gain a fuller understanding of the DUT Loading the Example Data You can use the Getting Started Exercise Empty example VI as a template VI to build an order analysis application that analyzes the example data with a variety of plots Complete the following steps to load the computer fan run up data to use in the Getting Started Exercise Empty example VI 1 Launch the Getting Started Exercise Empty example VI 2 Click the Browse button next to the Data path text box and
13. to compute and display the colormap of the computer fan run up data 1 Press the lt Ctrl E gt keys to switch to the block diagram of the Getting Started Exercise VI On the Order Analysis Express Measurements palette select the Spectral Map Express VI and place it on the block diagram A configuration dialog box appears Click the OK button to save the current configuration and close the configuration dialog box In this application you can use the default configuration settings when you run the Spectral Map Express VI for the first time Wire the waveform signal output of the oax_Load Data Analog Tacho single channel VI to the input signal input of the Spectral Map Express VI Wire the speed profile output of the Analog Tacho Processing Express VI to the speed profile input of the Spectral Map Express VI Wire the colormap output of the Spectral Map Express VI to the Colormap indicator The block diagram should appear similar to Figure 3 ab Control lagnitude Prder list Order waveform E babe 1 Prde power spectrum i p Analog Tacho Processing i Spectral Map t analog tacho sign eeren gt input signal speed profile gt gt speed profile olormay colormap gt eed profile 7 8 National Instruments Corporation Figure 3 Creating the Colormap Run the
14. Express VI to compute the magnitude of designated orders Recall that the Colormap plot showed the seventh order of the computer fan run up data has a strong amplitude at 2 600 RPM You can use a magnitude plot to observe this order in more detail Complete the following steps to compute and display the magnitude of the seventh order of the computer fan run up data 1 Press the lt Ctrl E gt keys to switch to the block diagram of the Getting Started Exercise VI 2 On the Order Analysis Express Measurements palette select the Order Tracking Express VI and place it on the block diagram A configuration dialog box appears 3 On the Configuration page set the Orders to track to 7 Getting Started with Order Analysis 12 ni com 4 Click the OK button to save the current configuration and close the configuration dialog box 5 Wire the waveform signal output of the oax_Load Data Analog Tacho single channel VI to the input signal input of the Order Tracking Express VI 6 Wire the speed profile output of the Analog Tacho Processing Express VI to the speed profile input of the Order Tracking Express VI 7 Wire the magnitudes output of the Order Tracking Express VI to the Magnitude indicator The block diagram should appear similar to Figure 9 gS list Bo waveform gt Spectral Map input signal Analog Tacho Processing i f analog tacho sign S
15. al an analog tachometer signal and information about the tachometer You also can see several indicators on the block diagram of the Getting Started Exercise VI You will use these indicators in later sections National Instruments Corporation 5 Getting Started with Order Analysis Complete the following steps to compute the rotational speed of the computer fan and to display the information in a speed profile plot 1 On the Order Analysis Express Measurements palette select the Analog Tacho Processing Express VI and place it on the block diagram of the Getting Started Exercise VI A configuration dialog box appears 2 On the Configuration page of the configuration dialog box set Pulse Revolution to 2 Recall that you acquire the pulse per revolution information in the Tacho info indicator when you run the Getting Started Exercise VI for the first time 3 Click the OK button to save the current configuration and close the configuration dialog box 4 Wire the analog tacho signal output of the oax_Load Data Analog Tacho single channel VI to the analog tacho signal input of the Analog Tacho Processing Express VI 5 Wire the speed profile output of the Analog Tacho Processing Express VI to the Speed profile indicator The block diagram should appear similar to Figure 2 g Tacho single channel vi pnput xara Ram olormap Order power spectrum Magnitude Order list Order waveform A bod H
16. ees Getting Started with Order Analysis NI Sound and Vibration Measurement Suite Version 5 0 This document provides an introduction to the order analysis tools that the NI Sound and Vibration Measurement Suite provides This document also contains exercises that you can use to learn how to build order analysis applications with the Order Analysis Express Measurements VIs These exercises take a short amount of time to complete and help you get started with the order analysis tools The following resources contain information you might find useful e LabVIEW Help available by selecting Help Search the LabVIEW Help e Getting Started with LabVIEW e LabVIEW Sound and Vibration Analysis User Manual Contents Introduction to Order Analysis eee eceeseesceseeseeeeceeeeseeeeeeseseeeeaeeeees 2 Order Analysis Applications eceeeeseesecseceseseeeeeeeeesseeseeeeeens 2 Performing Order Analysis with Example VIs 0 ee eeeeeeeee 3 Building an Order Analysis Application eee eeeeeeeeesereeeeneeeees 3 Description of the Device under Test 00 0 eee eeeeseeseeereeneeeeeees 3 Analyzing the Example Data 0 eee eeecceeseeeneeeeeeeeeceeeseaeeeneeeeees 4 Loading the Example Data 0 cece eeeeseeseeeeeeeeeseeeeeaes 5 Analyzing the Speed Profile 00 00 eee cece eseeseeeeeeeeeeeneeeaes 5 Analyzing the Colormap ccceecesseceeseeeseeseeeeeeseeeeeeseeseeeaes 7 Analyzing the Order Power Spectrum eee ee eeeeeeeeeees
17. ibration signal plot e Speed profile plot e Colormap e Order power spectrum e Magnitude plot e Order waveform National Instruments NI ni com and LabVIEW are trademarks of National Instruments Corporation Refer to the Terms of Use section on ni com 1legal for more information about National Instruments trademarks Other product and company names mentioned herein are trademarks or trade names of their respective companies For patents covering National Instruments products refer to the appropriate location Help Patents in your software the patents txt file on your CD or ni com patents 2007 National Instruments Corporation All rights reserved 374418A 01 Mar07
18. ighth orders together as shown in Figure 11 Order 7 Iw Magnitude Order 8 Iw Magnitude g rms t 1 1 i j j j 1 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 Speed RPM Figure 11 Magnitude Plot of the Seventh and Eighth Orders As you observed with both the Colormap plot and the Order power spectrum plot the amplitude of the eighth order increases as the amplitude of the seventh order decreases between 2 800 RPM and 3 000 RPM The Magnitude plot provides a detailed view of exactly how the two orders change in magnitude with changing speed In the configuration dialog box of the Order Tracking Express VI you can set the X axis selection of the Magnitude plot to display the order magnitude against time speed or number of revolutions You also can use Getting Started with Order Analysis 14 ni com the Magnitude View options to specify the type of quantitative measurement you want to use to calculate and display the magnitude Whereas an order power spectrum shows the magnitude or power values of all orders at a specific period in time or at a specific speed the Magnitude plot provides detailed information about particular orders that you specify Extracting Order Waveforms You can extract order waveforms to isolate specific orders from a sound or vibration signal The order waveform provides detailed information about the specific order you extracted from the input signal Y
19. navigate to the PC Fan runup dat file in the labview examples Order Analysis Example Data directory Click the OK button The filename appears in the Data path text box 4 Click the Run button to run the Getting Started Exercise Empty example VI 5 Select File Save As and save the VI as Getting Started Exercise vi in an easily accessible location The Getting Started Exercise VI displays the waveform of the computer fan run up data in the Input signal plot on the front panel This VI also returns the tachometer information for the input signal in the Tacho info indicator Notice that the number of pulses per revolution of the tachometer is two Analyzing the Speed Profile The Input signal plot of the Getting Started Exercise VI is a vibration signal plot Vibration signal plots illustrate how sound or vibration signals change over time You can use a speed profile plot to illustrate how rotational speed changes over time You then can use these two plots in parallel to observe how raw sound or vibration changes with speed The Analog Tacho Processing Express VI uses an analog tachometer signal to determine the rotational speed of a DUT You can use this Express VI to compute the rotational speed of the computer fan Press the lt Ctrl E gt keys to switch to the block diagram of the Getting Started Exercise VI Notice that the oax_Load Data Analog Tacho single channel VI loads the example data and returns the vibration sign
20. nd close the configuration dialog box Run the Getting Started Exercise VI again to extract and display the waveform of the seventh order of the computer fan run up data Save this VI 16 ni com On the front panel click the Order Waveform tab to display the Order waveform plot of the seventh order as shown in Figure 13 Amplitude O1 0 2 0 3 Order waveform 0 5 0 4 0 3 0 2 7 0 1 0 1 8 16 Time s Figure 13 Waveform of the Seventh Order You also can use the Order Waveform Express VI to extract multiple orders of a signal that generate the greatest amplitude or produce the strongest noise As you observed with the Colormap Order power spectrum and Magnitude plots the fourth seventh and eighth orders have relatively strong amplitudes in the computer fan run up data Complete the following steps to extract and display the waveforms of the combination of the fourth seventh and eighth orders 1 National Instruments Corporation Press the lt Ctrl E gt keys to switch to the block diagram of the Getting Started Exercise VI Double click the Order Waveform Express VI to display the configuration dialog box On the Order Selection page set Order to preview to 4 Click the Extract button to extract the order waveform of the fourth order Set Order to preview to 8 Click the Extract button to extract the order waveform of the eighth order In the Extracted
21. ou then can perform further analysis such as sound playback and sound synthesis on these significant orders Use the Order Waveform Express VI to extract order waveforms As you observed with the Colormap Order power spectrum and Magnitude plots the seventh order is one of the orders that has strong amplitude in the computer fan run up data You can use the Order Waveform Express VI to extract and display the order waveform of the seventh order of the computer fan run up data Complete the following steps to extract and display the order waveform of the seventh order from the computer fan run up data 1 On the Order Analysis Express Measurements palette select the Order Waveform Express VI and place it on the block diagram of the Getting Started Exercise VI A configuration dialog box appears 2 Click the OK button to save the current configuration and close the configuration dialog box In this application you can use the default configuration settings when you run the Order Waveform Express VI for the first time 3 Wire the waveform signal output of the oax_Load Data Analog Tacho single channel VI to the input signal input of the Order Waveform Express VI 4 Wire the speed profile output of the Analog Tacho Processing Express VI to the speed profile input of the Order Waveform Express VI 5 Wire the order list output of the Order Waveform Express VI to the Order list indicator National Instruments Corporation 15 Ge
22. tting Started with Order Analysis 6 Wire the order waveform output of the Order Waveform Express VI to the Order waveform indicator The block diagram should appear similar to Figure 12 ab Control Analog Tacho Processing Spectral Map ana gt input signal ia speed profile Eolormap colormap fi H gt Order Spectrum gt input signal gt speed profile Order power spectrum PLA F d Order Tracking gt input signal gt speed profile magnitudes ppm Psi ae gt Order Waveform acaenani gt input signal iem gt speed profile order waveform w 10 11 12 13 14 15 Getting Started with Order Analysis Figure 12 Extracting Order Waveforms Run the Getting Started Exercise VI Double click the Order Waveform Express VI to display the configuration dialog box You can see the colormap of the computer fan run up data in the Colormap plot On the Order Selection page set Order to preview to 7 Click the Extract button to extract the order waveform of the seventh order Select the seventh order in the Extracted orders list Click the Export button to export the order waveform of the seventh order to the block diagram Clicking the Export button also adds the seventh order to the Output list Click the OK button to save the current configuration a
23. und 2 600 RPM Getting Started with Order Analysis 8 ni com Colormap 8k 3 6k 3 4k 3 2k 3k 2 8k 2 6k 2 4k 2 2k 2k 1 8k 1 6k 6 swa gp apnyjdwy Speed RPM nS ra rE 9 10 11 12 13 14 15 16 17 18 19 20 Order Figure 5 RPM Order Plot With this Colormap plot you also can identify orders that correspond to loud noises or strong vibrations that you observe For example suppose the computer fan generates loud noises between 2 800 RPM and 3 000 RPM From the RPM Order plot you can see that the fourth and the eighth order contribute the most to the loud noises in this speed range 3 Click the OK button to save the current configuration and close the configuration dialog box A colormap plot therefore provides an overview of how the intensity of a signal relates to time speed frequency and order Analyzing the Order Power Spectrum An order power spectrum provides a quantitative description of the rotation related components of a signal You can use an order power spectrum to find and compare significant orders You can use the Order Spectrum Express VI to compute the order power spectrum of a sound or vibration signal As you observed with the Colormap plot the vibration amplitude of the seventh order is the strongest around 2 600 RPM You can use the Order Spectrum Express VI to compute the order power spectrum of the example data at 2 600 RPM and to find the significant orders
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