NI DIAdem analysis panel tutorial

Introduction to Analysis

The ANALYSIS panel allows you to perform analysis on the data loaded into the Data Portal (memory). Dialogs assist you in setting up and performing an extensive scope of standard mathematical functions for data analysis. These mathematical functions are organized into groups that you can browse via the menus, or the group bars. The DIAdem Calculator allows you to define your own custom formula based functions. The Calculation Manager will allow you to define a set of calculations to execute where the output from one calculation may be passed as input to the next calculation.

ANALYSIS Panel GUI

When you activate the ANALYSIS panel by clicking on it, the graphical user interface (GUI) changes, displaying a blank output area in the middle of the application. The menu structure at the top of the DIAdem application window, and the group bars along the inside left organize the mathematical functions available for data analysis. The function group names are: Basic Mathematical, Channel Calculations, Curve Fitting, Signal Analysis, Statistical and Classification, 3D Analysis, and Crash Analysis. Make sure the Data Portal is visible by using the keystrokes 'Alt-F6' if it is not.

The Calculation Manager is accessed by either clicking on the ANALYSIS 'File' menu and then choosing 'Calculation Manager...', or by clicking on the toolbar icon labeled 'Calculation Manager'. The calculator is activated by clicking on the ANALYSIS toolbar icon labeled 'Calculator', or from the menu 'Basic', 'Calculator...'.

Choosing a mathematical function from the menu or the group bar launches a dialog that will typically accept one or more channels for input.

Find the example file that comes with the DIAdem installation named 'Example.tdm' located in 'C:\PROGRAM FILES\NATIONAL INSTRUMENTS\DIADEM 2021\Libr\Data\Example.tdm' and load that file into memory (the Data Portal).

Calculating Descriptive Statistics on a Channel

From the ANALYSIS menu 'Statistics', choose the option 'Descriptive Statistics...'. In the 'Descriptive Statistics' dialog, under 'Object to be analyzed', click on the button labeled '...' to the right of the 'Channels:' label and input field. Another dialog will appear named 'Select Channels'. Use the button labeled 'X' to delete any channels already in the list. Then expand the channel group named 'Noise data', and then drag and drop the channel 'Noise_2' to the channel list area in the 'Select Channels' dialog. When done, click 'OK'.

On the 'Characteristic Values 1' tab, click the 'All Off' button, and then in the 'Mean values' section, enable the checkbox labeled 'Root mean square'. The calculation will appear immediately in the 'Result data' section.

Click on the tab labeled 'Result Storage' and make sure the checkbox labeled 'Store results in channels' is not checked. Calculation of the RMS, as well as all other calculations available from this dialog result in a single numeric value. The default is to add that result to the channel(s) being analyzed as a new property. Click the 'Calculate' button, and then the 'Close' button.

Examine the properties for the channel 'Noise_2' in the Data Portal. Under 'Custom Properties', you will see the RMS result saved under the property named 'Result~Statistics~MeanValues~SquareMean'. Note that the tilde '~' character is used here to indicate the property hierarchy. The results of all ANALYSIS functions in DIAdem are either stored as properties or new channels.

Note also that in the ANALYSIS window, a sort of log was written, indicating what calculation was performed, on what channel, the DIAdem script function used to perform the calculation ('ChnStatisticsCalc()'), and the numerical result for the root mean square.

The Time Series Data Mangement System is an application built on NI DIAdem that can calculate channel statistics on a set of channels automatically across thousands of individual files, and then generate a report with those results. An always free 'Base Edition' is available for download.

Smoothing A Channel

DIAdem has three smoothing filters to assist with managing signal noise. From the 'Curve Fitting' menu, you can see them at the top with the labels 'Smooth...', 'Smooth with 4353H filter...', and 'Smooth with Savtizky-Golay Filter...'. Unfortunately, DIAdem has not integrated these three filter options that have evolved over time into a single interactive dialog. You need to try each one manually to find the best result for your needs. We will explore using each of these filters on the channel 'Noise_2' in the channel group 'Noise data'.

From the ANALYSIS panel menu 'Curve Fitting', choose the filter option 'Smooth...'. Drag and drop the 'Noise_2' channel into the channel input area. Make sure the 'Calculation parameters' are set to the default values of: 'Max smoothing width on one side (no of points):' to 12, 'Select points:' to 'Maximum number', 'Smoothing procedure' is 'Smooth over mean value', and 'Result channel' does not have the checkbox 'Store result in original channel checked. A plot will be shown in the dialog to give you an idea what impact the filter will have on the data. Unfortunately, you cannot zoom in and see specific sections of the data, but in this case you can see that the filter is too aggressive. Try changing the 'Max smoothing width on one side' option, and the other parameters as well. When finished, click the 'Cancel' button so that no changes are saved.

From the ANALYSIS menu 'Curve Fitting', choose the filter 'Smooth with 4253H Filter'. Drag and drop the 'Noise_2' channel to the channel input control. Notice that this filter is much less aggressive than the 'Smooth' filter. The spikes in the signal are filtered to some degree, but it is not clear from the preview if the outcome will be acceptable. Choose the 'Smooth with 4253H-twice-filter' option, make sure the checkbox 'Store result in original channel' is not checked, and then click the 'Calculate' button, observing what happens in the Data Portal, and then click the 'Cancel' button to close the 'Smooth with 4253H Filter' dialog.

A new channel will be added to the default channel group in the Data Portal. Move that channel back under the channel group 'Noise data' by selecting the channel 'Smoothed4253H', right click and choose 'Cut' from the pop up window. Then navigate back up to the 'Noise data' channel group, click on the channel group, and then right click and choose 'Paste'.

Lets examine the filtered results more closely by using the VIEW panel. Activate the VIEW panel, and choose the 'File', 'New' option to clear out the worksheet area (don't save anything that was left behind). Click on the channel 'Noise_2' and then the channel 'Smoothed4253H' and then drag and drop in to the empty VIEW worksheet. Choose the '2D Axis System' option. Use the Band Cursor to zoom in to the section between 3.908 and 3.91 seconds. Note by toggling the checkbox for the green curve (Smoothed4253H), you can see the effect of the filter on the signal. You would need to decide if this filtering is good. Note that if you calculate RMS on the filtered channel, you will see that it has changed from 0.128 to 0.120.

Try the final filter named 'Smooth with Savitzky-Golay Filter'. Drag and drop the 'Noise_2' filter to the channel input control. Notice that in the preview area, the a message states the preview has been aborted because the channel has many values (325000 in fact). Therefore, the only way to see the result is to plot it in the VIEW panel. Make sure the defaults are set to: 'Smoothing width on one side:' to 12, 'Order of the polynomial:' to 1, and 'Weighting channel' checkbox is unchecked. ' After confirming that the 'Store result in original channel' is unchecked, click the 'Calculate' button to execute the filtering, and then the 'Close' button to close the dialog. Drag the channel created 'FilteredSignal' back to the channel group 'Noise data'.

Activate the VIEW panel and then drag and drop the channel 'FilteredSignal' to the 2D chart. Note that the effect of the 'Savitzky-Golay' filter is significantly different than the '4253H' filter.

Try the 'Savitzky-Golay' filter again, but this time change the 'Smoothing width on one side:' to 3. Plot that result in the VIEW panel as done before. You can see that the 'Savitzky-Golay' filter with a value of 3 (channel 'FilteredSignal1') produces a result that is somewhere between the 'Smoothed4253H' result, and the 'Savitzky-Golay' filter value 12 (channel 'FilteredSignal').

Clear out the VIEW sheet by clicking on the VIEW menu options 'File' and 'New' (don't save). Clear out the Data Portal by clicking on the NAVIGATOR panel and then the menu options 'File' and 'New' (don't save). Load the 'Example.tdm' file again by choosing 'File' and 'Recent Files'.

Finding A Channel Event

This tutorial will demonstrate how DIAdem can identify a channel event based on criteria for two channel conditions. DIAdem has two dialogs to assist with an event search task. From the ANALYSIS panel, browse the menu option 'Channel Functions', and select either 'Event Search' or 'Event Search (Free Formula)'. It is the author's opinion that 'Event Search (Free Formula)' is easier to use.

From the ANALYSIS panel, browse the menu option 'Channel Functions', and select 'Event Search (Free Formula)'. The dialog 'Event Search (Free Formula) will appear. Clear out the dialog inputs so they appear as shown below.

We want to look for the condition where the channel 'Speed' has a value greater than 40 m/s, and the channel torque is greater than 200 Nm. Under the section 'Channels to be analyzed', click on the first row in the table to the right of the label '1' under the column 'Identifier' and assign the value of 'A'. To the right of that, drag and drop the channel 'Example/Speed' from the Data Portal into the field labeled 'Channel'. Click on the '+' icon to add another condition and then repeat the process for the channel 'Torque', but assigning the 'Identifier' of value 'B'. At the bottom of the dialog, the tab 'Result Storage' and options 'Condition fulfilled' and 'Condition not fulfilled' establish what the result channel output will be. You want the value to be '1' when fulfilled (true), and '0' when not fulfilled (false). At the top of the dialog, enter the 'Formula' value of '(A>40) AND (B>200)'. The dialog should appear as shown below.

The 'Result data' plot on the bottom right will show graphically when the data will meet the conditions for the 'Selected channel' plotted above. Click the 'Calculate' button at the bottom of the screen, and then click the 'Close' button.

DIAdem will create a new channel named 'EventStatus' in the last channel group in the Data Porta. Drag this channel up to the channel group 'Example' where it belongs.

Visualizing Event Search Results

This tutorial will use the 'EventStatus' channel created from the prior tutorial event search to visually identify where in the 'Speed' and 'Torque' channels the events occurred. The visualization will be performed in a VIEW 2D Axis System using 'Background Segments'.

Click on the VIEW panel to activate it. Clear out the worksheet by choosing the menu option 'File', 'New'. Select the 'Time', 'Speed', and 'Torque' channels in the 'Example' channel group and then drag and drop them to the empty VIEW worksheet. When the pop up menu appears, choose '2D Axis System'. Access the 2D Axis System toolbar 'Y-Axis' and select the option 'n Systems [linear]'.

From the VIEW panel menu, choose 'View' and 'Settings' (or double click inside the 2D Axis System area, but not the legend area). Click on the button 'Background Segments...'.

Delete any existing segment definitions if they exist. Click on the '+' button labeled 'New Entry' when you hover your mouse over it. The 'Add Segment' dialog will appear. Drag and drop the 'Time' channel from the Data Portal to the 'Add Segment' dialog 'X-channel' channel input control. Drag and drop the 'EventStatus' channel from the Data Portal to the 'Add Segment' dialog 'Y-channel' channel input control. Make sure the 'Type:' is set to 'X', the 'Color' is set to grey, and the 'Transparency' is set to '0'. Click the 'OK' button to close the 'Add Segment' dialog. Click the 'OK' button to close the 'Color Background Segments' dialog. Click the 'OK' button to close the '2D Axis System' dialog.

The 2D chart now displays the 'EventStatus' channel in the background, allowing you to visualize when the where the channel 'Speed' has a value greater than 40 m/s, and the channel torque is greater than 200 Nm.

Clear the VIEW worksheet by accessing the menu 'File', 'New'. Clear out the Data Portal by clicking on the NAVIGATOR panel and then the menu options 'File' and 'New' (don't save). Load the 'Example_data.tdm' file again by choosing 'File' and 'Recent Files'.

Calculator & Calculation Manager

You can perform custom channel calculations using the 'Calculator' and the 'Calculation Manager'. The Calculation Manager is recommended over the Calculator several reasons, as will be demonstrated by the examples that follow.

The tutorial that follows will calculate power from the RPM and Torque channels from the 'Example.tdm' DIAdem sample file. Find the example file that comes with the DIAdem installation named 'Example.tdm' located in 'C:\PROGRAM FILES\NATIONAL INSTRUMENTS\DIADEM 2021\Libr\Data\Example.tdm' and load that file into memory (the Data Portal).

Channel References for Calculator & Calculation Manager

DIAdem uses the format of Ch("group name / channel name") to reference a channel within formulas for both the Calculator and the Calculation Manager. For example, if you wanted to reference a channel named 'Noise_1' in the channel group named 'Noise data', then the reference would be: Ch("Noise data/Noise_1") . If the channel "Noise_2" is a unique name to all channels currently in the Data Portal, then you can simplify the reference to just the channel name, e.g. Ch("Noise_1") . When you are creating a new channel to receive the results of the calculation, make sure to always include the channel group name.

Both the Calculator and the Calculation manager will create a new channel in an existing default channel group, or a new channel group. Using 'Ch("NewChnGrp/NewChn") = PI' for example as the formula (exclude the outer single quotes) will result in a new channel group named 'NewChnGrp' and a new channel named 'NewChn' to be created in the Data Portal (assuming neither already exist). If the channel already exists, it will be overwritten.

Calculating Power Using Calculator

The general formula to calculate power in kW from Torque in N-m and speed in RPM is:

Power [kW] = 2 * Pi() * (1 min / 60 sec) * (1 kW / 1000 W) * (Speed [rpm]) * (Torque [N-m])

Access the Calculator by clicking on the ANALYSIS panel toolbar labeled 'Calculator', or from the menu 'Basic', 'Calculator...'. Click in the 'Formula' window, and enter the following formula (excluding the leading and trailing single quotes): 'Ch("Example/Power_kW") = Ch("RPM") * Ch("Torque") * 2 * PI * (1/60) * (1/1000)'

If you press the enter key on your keyboard after entering / pasting the formula, then the formula will execute. Otherwise, you can perform the calculation by click the 'Calculate' button.

After the calculation executes, a new channel named 'Power_kW' will be created in the Data Portal with the result. Note that no units are assigned to this channel, and it is necessary to enter constants in order to convert the speed from RPM to rotations per second, and the power from watts to kilowatts. As a convenience, the 'Description' property for the channel is updated with the formula from the Calculator.

Calculating Power Using Calculation Manager

Click on the channel 'Power_kW' created by the prior exercise and then right click and choose 'Delete' to remove the channel. Launch the Calculation Manager by either using the menu option 'File', 'Calculation Manager...', or clicking on the calculation manager icon.

Create a new Calculation Group by clicking on the 'Add Calculation Group' toolbar button. Name the calculation group 'Power' and click the 'OK' button.

Click on the dialog toolbar 'Add Calculation'. The dialog 'Calculation Manager - Add Calculation' will appear. Two buttons are at the top, 'Calculation' and 'Script'. Click the 'Calculation' button at the top. Assign a name to the calculation. Set the 'Formula:' to : 'Ch("Example/Power_kW") = Ch("RPM") * Ch("Torque")' Make sure the 'Quantity-based' checkbox is checked, and then to the right of that at 'Result unit:', click on the '...' button and find the 'Quantity' of 'Power' and assign the value of 'kW'. Click on the 'Script' button at the top of the dialog and observe the VBScript code that is shown to replicate the calculation. Click the 'OK' button when finished.

Note that the formula 'Ch("Example/Power_kW") = Ch("RPM") * Ch("Torque")' does not contain any constants for unit conversion. This is because the 'Quantity-based' checkbox is selected, and a target final unit of 'kW' was assigned. The conversions required to convert torque in N-m and speed in rotations per minute (rpm) to kilowatts is automatically figured out by DIAdem. HOWEVER, if the 'Torque' or 'RPM' channel didn't have units, then this option would generate an error, and it would be necessary to input the unit conversions as was done with the Calculator.

The dialog should be configured as shown in the image below. Click on the toolbar 'Run' button to execute the calculation. Observe that the 'Power_kW' channel is created in the Data Portal.

In order to demonstrate a sequence of calculations, we will add one more calculation that will convert power and speed (rpm) back to torque. Click the 'Add Calculation' button. Assign a 'Name:' of 'Torque_Nm'. Enter the formula: 'Ch("Example/Torque_Nm") = Ch("Power_kW") / Ch("RPM")' Check the checkbox 'Quantity-based' and set the 'Result unit' to 'N-m' by looking under 'Quantity' = 'Torque' and selecting '[Nm] newton meter'. Click the 'Run' button at the top right toolbar to see the result. Click the 'OK' button to close the 'Calculation Manager - Add Calculation' dialog.

With the 'Calculation Manger' dialog still visible, click the save button on the toolbar and give it the name 'Power_Torque.tca', taking note where the file was saved. Click the 'OK' button to close the dialog. In the Data Portal, select the 'Power_kW' and 'Torque_Nm' channels and then click the keyboard key 'Del' to delete those two channels (or right click and choose 'Delete'). Click on the ANALYSIS toolbar button 'Execute Calculations' button. Select the first row labeled 'Power' (in the 'Calculation' column it shows '--- 2 Calculation(s) ---'). Click on the toolbar button 'Run'. Observe that both calculations run. First the 'Power_kW' channel is created, and then it is followed by the 'Torque_Nm' calculation.

As demonstrated, you can sequence a series of calculations, where one depends on the result of a prior calculation to generate a new output. This is a powerful no script method of automating calculations.

What You Learned

DIAdem has a wide scope of powerful analysis functions. Dialogs guide you through the use of each of the functions.
You can use event search to identify when one or more channels both meet a particular condition, and then visualize the result in the VIEW panel using Background Segments.
The Calculation Manger is a tool that allows you to easily chain a sequence of calculations where one calculation result becomes another calculation's input (script / code writing not required).

Custom Unit Set 'US_TestLab'
Quantity	Units
Angular velocity	rad/s, 1/s °/s
Power	hp, Btu/h
Speed	mph
Torque	ft-lb

FFT

The Fast Fourier Transform (FFT) provides you with the frequency content of time domain signal(s) in the frequency domain. Any signal can be thought of as a sum of a series of simple sinusoids of different frequencies, amplitudes, and phases. Fourier analysis or spectrum analysis will deconstruct a signal into its individual sine wave components. The result is the vibration amplitude as a function of frequency. The highest frequency that can be analyzed from a signal is limited by the one half the sample rate of the signal (Nyquist frequency). The duration of the signal analyzed will limit the frequency resolution. For a sample rate of Fs in Hz, and a recording duration of T in seconds, The frequency resolution in Hz will be Fs / T, and the maximum frequency in Hz that can be analyzed will be Fs/2. For the best FFT results, record the data at 10x the highest frequency you expect to analyze.

DIAdem provides several FFT calculations, including 'FFT (One Time Signal)', 'Inverse FFT', 'FFT (Two Time Signals)', and 'Full Spectrum FFT'. All of these functions except for 'Inverse FFT' support various window functions, time interval options, and amplitude options of peak amplitude, RMS amplitude, power spectrum, autospectrum, and power spectral density (PSD). It is important to choose the correct amplitude option, otherwise the results might be incorrectly interpreted. The table below will help you to identify the best calculation and options, based on the application.

Identify Calculation by Application
The Data	Analysis	Calculation
Rotational Vibration	Identify the finite number of dominate frequency components. 'Characterize Oscillation' calculates the frequency with the greatest amplitude. (See also rotating shaft analysis)	FFT (One Time Signal) peak amplitude
Rotating Shaft Analysis	Calculate full spectrum FFT for accelerometers positioned perpendicular to positions on a shaft. Analyze the movement of shaft center. Evaluate tachometer pulse signals measured by a sensor on a shaft. Calculate the amplitude and phases for each order for a Bode diagram.	(Ex of all below) Full Spectrum FFT Shaft Centerline Pulse Detection Order Analysis for Bode Display
Random Vibration FFT Comparison	Calculate the frequency content for a signal with no dominate frequency components. Compare FFT of signals with with different sample rate and recorded duration.	FFT (One Time Signal) power spectral density
Third/Octave Analysis	Examine the volume in frequency intervals, not the exact frequency distribution in the signal.	FFT (One Time Signal) Third/Octave
Stimulation & Response Signal Pairs	A forcing function (stimulation) is measured in addition to the response	FFT (Two Time Signals) peak amplitude
Shock Response Spectrum (SRS)	Determine how a single degree-of-freedom system with different hypothetical natural frequencies would respond to a shock.	Shock Response Spectrum (SRS)
Oscillation Characteristics	Characterize an oscillation signal in terms of the frequency with the greatest amplitude, and determine the phase angle. Calculate the ratio of the total signal power to the distortion signal power in decibels.	Characterize Oscillation SINAD Analysis
Sound	Characterize the volume in human perception terms.	FFT (One Time Signal) peak amplitude Third/Octave
Acoustic	Apply frequency weighted digital filtering to a noisy signal. The frequency weighting A,B,or C as defied by IEC 61672-1:2003 and DIN EN 61672-1:2003-10 norms can be applied. The human ear has varying sensitivity to differrent frequencies and acoustic pressures.	Frequency Weighting (A-B-C-Filtering)
Environmental Vibrations	Characterize how vibrations affect the human body relative to industry standards.	Frequency-Weighted Acceleration
Signal-to-Noise and Distortion Ratio	Calculate the ratio of the total signal power to the distortion signal power in decibels.	SINAD Analysis
DC Bias Removal	Remove the DC bias from a signal.	AC/DC Coupling

'Calculation' - the specific name assigned in the ANALYSIS panel menu 'Signal Analysis'.

FFT (One Time Signal)

Calculates the real part and the imaginary part of the transformed signal. Thereafter, calculates the phase and amplitudes of the frequency response. The amplitude may be calculated as peak amplitude, RMS amplitude, power spectrum, autospectrum, or power density spectrum (details follow). The window options of 'Rectangle' or 'Hanning' are usually the best choice. A pulse that decays over time is best analyzed with a 'Exponential' window. Applications involving a forcing function (stimulation) that is measured in addition to the response should use the 'FFT (Two Time Signals)' calculation option. The examples below are organized by the amplitude calculation options.

Peak Amplitude

The most common amplitude option. This is the best choice when analyzing a single signal with a finite number dominate frequency components. However, if you need to compare signals with different sample rates and recorded durations, then the 'power spectral density' (PSD) amplitude option is a better choice.

This first example will analyze a signal consisting of a composite of two sine waves with a frequency of 3 Hz and 40 Hz. Generate simulated acceleration data by running the script below.


'Generate simulated acceleration data that consists of 2x sine waves added 
'together.  The first sine wave is 3 Hz with an amplitude of 2 g. 
'The second sine wave is 40 Hz with an amplitude of 0.5 g.

Dim oGrp, oChnTime, oChnAcceleration
Call Data.Root.Clear()
Set oGrp = Data.Root.ChannelGroups.Add("FFT SIN7Hz40Hz")

'Generate simplated simulated acceleration data channels...
Set oChnAcceleration = oGrp.Channels.Add("Acceleration",DataTypeChnFloat64)
oChnAcceleration.UnitSymbol = "m/s^2"
Call SigGenAccelUpsPkg(oChnTime, oChnAcceleration)

'Compare the curves in the VIEW panel 
Call View.NewLayout()
Dim oSheet, oAreaTop, oAreaCenter, oAreaBottom, o2DCurve
Set oSheet = View.ActiveSheet
Set oAreaTop = oSheet.ActiveArea
oAreaTop.Name = "Top"
Set oAreaBottom = oAreaTop.SplitBottom("BottomArea",0.33)
Set oAreaCenter = oAreaTop.SplitBottom("CenterArea",-1)

oAreaTop.DisplayObjType = "CurveChart2D"   
' "1 system [phys.]"  "n systems [phys.]"  "n axes [phys.]"  
oAreaTop.DisplayObj.YScaling = "1 system [phys.]"
Set o2DCurve = oAreaTop.DisplayObj.Curves2D.Add(oChnTime.GetReference(eRefTypeIndexName),oChnAcceleration.GetReference(eRefTypeIndexName))

Call WndShow("VIEW")

Sub SigGenAccelUpsPkg(oChnX, oChnY)
  ' Generate a simulated acceleration signal for UPS package shipment 
  ' consisting of a 3 Hz sine wave with an amplitude of 2 g, and a 
  ' 40 Hz sine wave with an amplitude of 0.5 g.
  ' FFT peak amplitude and power spectral density analysis will detect the 
  ' 3 Hz and 40 Hz frequencies. 

  Dim oGrp, oElementList, oChnSine3Hz, oChnSine40Hz
  Dim bUIAutoRefresh, bViewAutoRefresh: bUIAutoRefresh = UIAutoRefresh: bViewAutoRefresh = View.AutoRefresh
  Call UIAutoRefreshSet(False): View.AutoRefresh = False
  
  Set oGrp = oChnY.ChannelGroup
  
  '1 kHz sample rate, 3 hZ sine, 2 g amplitude
  Set oChnSine3Hz = oGrp.Channels.Add("Sine3Hz",DataTypeChnFloat64)
  oChnSine3Hz.UnitSymbol = "m/s^2"
  'ChnGenSignal(GenSignalFunction, GenSignalNoOfValues, GenSignalSamplingRate, ResultChannel, GenSignalFrequency, GenSignalAmplitude, GenSignalPhaseShift, GenSignalOffset, GenSignalTimeUnit, GenSignalUnit, GenSignalDutyCycle) 
  Call ChnGenSignal("Sine", 1024, 1000, oChnSine3Hz, 3, 2.0*9.81, 0, 0, "s", oChnSine3Hz.UnitSymbol, 50)
  'oChnSine3Hz is a waveform channel. Convert it to numeric, and assign the time channel to oChnX
	If ProgramRevision => 2100 Then 
		Set oElementList =  ChnConvertWaveformToNumeric(oChnSine3Hz, False, "WfXRelative")
	Else
		Set oElementList =  WfChnToChn(oChnSine3Hz, False, "WfXRelative")
	End If
  Set oChnX = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceNameName))
  Call ChnValExpand(oChnX)
  oChnX.UnitSymbol = "s"
  Call Data.Move(oChnX, oGrp, 1)
  
  '1 kHz sample rate, 40 hZ sine, 0.5 g amplitude
  Set oChnSine40Hz = oGrp.Channels.Add("Sine40Hz",DataTypeChnFloat64)
  oChnSine40Hz.UnitSymbol = "m/s^2"
  'ChnGenSignal(GenSignalFunction, GenSignalNoOfValues, GenSignalSamplingRate, ResultChannel, GenSignalFrequency, GenSignalAmplitude, GenSignalPhaseShift, GenSignalOffset, GenSignalTimeUnit, GenSignalUnit, GenSignalDutyCycle) 
  Call ChnGenSignal("Sine", 1024, 1000, oChnSine40Hz, 40, 0.5*9.81, 0, 0, "s", oChnSine40Hz.UnitSymbol, 50)
  'Convert oChnSine40Hz from waveform to numeric
	If ProgramRevision => 2100 Then 
		Set oElementList =  ChnConvertWaveformToNumeric(oChnSine40Hz, False, "WfXRelative")
	Else
		Set oElementList =  WfChnToChn(oChnSine40Hz, False, "WfXRelative")
	End If
  Call oGrp.Channels.Remove(oElementList.Item(1).Name)
  
  'Add the two sine channels to create the acceleration channel
  Call ChnAdd(oChnSine3Hz, oChnSine40Hz, oChnY)
  Set oChnY.XRelation = oChnX
  oChnY.UnitSymbol = oChnSine40Hz.UnitSymbol
  
  'Delete the two sine channels
  Call oGrp.Channels.Remove(oChnSine3Hz.Name)
  Call oGrp.Channels.Remove(oChnSine40Hz.Name)
  
  Call UIAutoRefreshSet(bUIAutoRefresh): View.AutoRefresh = bViewAutoRefresh': Call View.Refresh()
End Sub 'SigGenAccelUpsPkg()

From the ANALYSIS panel, choose the menu options 'Signal Analysis', 'FFT (One Time Signal)...'. Drag and drop the 'Acceleration' channel from the Data Portal to the dialog channel control labeled 'Signal channels:'. The channel control 'Time channel:' should be automatically assigned to '[1]/Time' because the XRelation is set for 'Acceleration', otherwise make the assignment manually. Configure the dialog options exactly as shown below. Click the 'Calculate' button to perform the analysis, and then close the dialog.

Review the dominate frequencies identified by plotting the generated channels in a VIEW panel sheet. Activate the VIEW panel. In the Data Portal, select the 'Frequency' channel first, and then the 'AmplitudePeak' channel. Drag and drop the channels into the VIEW sheet center area. A popup menu will appear, choose the '2D Axis System' option. (help). Use the 2D Axis System toolbar 'Band Zoom' to zoom into the range of 0 to 100 Hz (help). Use the VIEW toolbar 'View Cursor' to see the values for the highest peak in the channel (help). The maximum amplitude is 19.2 mm/s^2 at 2.93 Hz. Use the VIEW toolbar 'View Cursor' to see the values for the second highest peak in the channel of 4.83 m/s^2 at 40.0 Hz.

The largest amplitude may also be obtained by using the DIAdem ANALYSIS function 'Characterize Oscillation'. Activate the ANALYSIS panel and choose the menu options 'Signal Analysis', 'Characterize Oscillation...'. Drag and drop the 'Acceleration' channel from the Data Portal to the dialog channel control labeled 'Signal channels:'. The channel control 'Time channel:' should be automatically assigned to '[1]/Time' because the XRelation is set for 'Acceleration', otherwise make the assignment manually. Set the 'Search criteria' to 'Browse entire frequency domain'. In the lower right of the dialog, you will see the results of 19.6 m/s^2 at 3.0 Hz and phase angle of 0.0 degrees. Click the 'Calculate' button and the result data will be added as properties to the channel 'Acceleration'. Click the 'Close' button to close the dialog.

The script below will replicate the manual actions performed above, generating the VIEW sheet and areas as shown following the VBScript code.


'Generate simulated acceleration data that consists of 2x sine waves added 
'together.  The first sine wave is 3 Hz with an amplitude of 2 g. 
'The second sine wave is 40 Hz with an amplitude of 0.5 g.
'Perform a FFT (One Time Signal) calculation on the channels.
'Perform a FFT (Characterize Oscillation) calculation on the channels.

Dim oGrp, oChnTime, oChnAcceleration, oElementList
Call LogFileDel()
Call Data.Root.Clear()
Set oGrp = Data.Root.ChannelGroups.Add("FFT SIN7Hz40Hz")

'Generate simplated simulated acceleration data channels...
Set oChnAcceleration = oGrp.Channels.Add("Acceleration",DataTypeChnFloat64)
oChnAcceleration.UnitSymbol = "m/s^2"
Call SigGenAccelUpsPkg(oChnTime, oChnAcceleration)

'Plot the channels created in the VIEW panel 
Call View.NewLayout()
Dim oSheet, oAreaTop, oAreaCenter, oAreaBottom, o2DCurve
Set oSheet = View.ActiveSheet
Set oAreaTop = oSheet.ActiveArea
oAreaTop.Name = "Top"
Set oAreaBottom = oAreaTop.SplitBottom("BottomArea",0.33)
Set oAreaCenter = oAreaTop.SplitBottom("CenterArea",-1)

'Plot channels oChnTime and oChnAcceleration in the VIEW sheet top area
oAreaTop.DisplayObjType = "CurveChart2D"   
' "1 system [phys.]"  "n systems [phys.]"  "n axes [phys.]"  
oAreaTop.DisplayObj.YScaling = "1 system [phys.]"
Set o2DCurve = oAreaTop.DisplayObj.Curves2D.Add(oChnTime.GetReference(eRefTypeIndexName),oChnAcceleration.GetReference(eRefTypeIndexName))

FFTIndexChn      = False
'----------- Window Functions -----------
FFTWndFct        = "Rectangle"
FFTWndPara       = 10
FFTWndChn        = oChnAcceleration.GetReference(eReferenceIndexName)
FFTWndCorrectTyp = "No"
'------------ FFT Functions -------------
FFTCalc          = False
FFTAmpl          = True
FFTPhase         = False
FFTCepstrum      = False
FFTAmplType      = "Ampl.Peak"
FFTAverageType   = "No"
FFTAmplExt       = "No"
FFTAmplFirst     = "Amplitude"
'------------ Time Intervals ------------
FFTIntervUser    = "all"
FFTIntervOverl   = 0
FFTNoV           = False
FFTIntervPara(1) = 1
FFTIntervPara(2) = oChnAcceleration.Size
FFTIntervPara(3) = 1
'------------ Command -------------------
Set oElementList = ChnFFT1(oChnTime, oChnAcceleration)

'Plot channels Frequency and AmplitudePeak in the VIEW sheet center area
oAreaCenter.DisplayObjType = "CurveChart2D"   
' "1 system [phys.]"  "n systems [phys.]"  "n axes [phys.]"  
oAreaCenter.DisplayObj.YScaling = "1 system [phys.]"
Set o2DCurve = oAreaCenter.DisplayObj.Curves2D.Add(oElementList.Item(1).GetReference(eRefTypeIndexName),oElementList.Item(2).GetReference(eRefTypeIndexName))
oSheet.Cursor.X1 = 0.0
oSheet.Cursor.X2 = 60.0
oAreaCenter.DisplayObj.XScalingMode = "RangeZoom"
oSheet.Cursor.Type="Band"
'Perform a 'Characterize Oscillation' calculation...
Call ChnSingleToneExtract(oChnTime, oChnAcceleration, 0, 10)
Call LogFileWrite("Max amplitude of " & Str(oChnAcceleration.Properties("Result~SingleTone~Amplitude").Value,"AutoAdj") & " " & oChnAcceleration.UnitSymbol & " at "  & Str(oChnAcceleration.Properties("Result~SingleTone~Frequency").Value,"AutoAdj") & " " & Data.GetChannel(oElementList.Item(1).GetReference(eRefTypeIndexName)).UnitSymbol & " and a phase angle of " & Str(oChnAcceleration.Properties("Result~SingleTone~Phase").Value,"AutoAdj") & " degrees")
'Show the 'Characterize Oscillation' calculation results in the VIEW panel sheet bottom area
oAreaBottom.DisplayObjType = "TextBox"   
oAreaBottom.DisplayObj.Alignment = "Center"
oAreaBottom.DisplayObj.Font.Size = 14
oAreaBottom.DisplayObj.Text = "Max amplitude of " & Str(oChnAcceleration.Properties("Result~SingleTone~Amplitude").Value,"AutoAdj") & " " & oChnAcceleration.UnitSymbol & " at "  & Str(oChnAcceleration.Properties("Result~SingleTone~Frequency").Value,"AutoAdj") & " " & Data.GetChannel(oElementList.Item(1).GetReference(eRefTypeIndexName)).UnitSymbol & " and a phase angle of " & Str(oChnAcceleration.Properties("Result~SingleTone~Phase").Value,"AutoAdj") & " degrees"

Call View.Refresh()
Call WndShow("VIEW")



Sub SigGenAccelUpsPkg(oChnX, oChnY)
  ' Generate a simulated acceleration signal for UPS package shipment 
  ' consisting of a 3 Hz sine wave with an amplitude of 2 g, and a 
  ' 40 Hz sine wave with an amplitude of 0.5 g.
  ' FFT peak amplitude and power spectral density analysis will detect the 
  ' 3 Hz and 40 Hz frequencies. 

  Dim oGrp, oElementList, oChnSine3Hz, oChnSine40Hz
  Dim bUIAutoRefresh, bViewAutoRefresh: bUIAutoRefresh = UIAutoRefresh: bViewAutoRefresh = View.AutoRefresh
  Call UIAutoRefreshSet(False): View.AutoRefresh = False
  
  Set oGrp = oChnY.ChannelGroup
  
  '1 kHz sample rate, 3 hZ sine, 2 g amplitude
  Set oChnSine3Hz = oGrp.Channels.Add("Sine3Hz",DataTypeChnFloat64)
  oChnSine3Hz.UnitSymbol = "m/s^2"
  'ChnGenSignal(GenSignalFunction, GenSignalNoOfValues, GenSignalSamplingRate, ResultChannel, GenSignalFrequency, GenSignalAmplitude, GenSignalPhaseShift, GenSignalOffset, GenSignalTimeUnit, GenSignalUnit, GenSignalDutyCycle) 
  Call ChnGenSignal("Sine", 1024, 1000, oChnSine3Hz, 3, 2.0*9.81, 0, 0, "s", oChnSine3Hz.UnitSymbol, 50)
  'oChnSine3Hz is a waveform channel. Convert it to numeric, and assign the time channel to oChnX
	If ProgramRevision => 2100 Then 
		Set oElementList =  ChnConvertWaveformToNumeric(oChnSine3Hz, False, "WfXRelative")
	Else
		Set oElementList =  WfChnToChn(oChnSine3Hz, False, "WfXRelative")
	End If
  Set oChnX = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceNameName))
  Call ChnValExpand(oChnX)
  oChnX.UnitSymbol = "s"
  Call Data.Move(oChnX, oGrp, 1)
  
  '1 kHz sample rate, 40 hZ sine, 0.5 g amplitude
  Set oChnSine40Hz = oGrp.Channels.Add("Sine40Hz",DataTypeChnFloat64)
  oChnSine40Hz.UnitSymbol = "m/s^2"
  'ChnGenSignal(GenSignalFunction, GenSignalNoOfValues, GenSignalSamplingRate, ResultChannel, GenSignalFrequency, GenSignalAmplitude, GenSignalPhaseShift, GenSignalOffset, GenSignalTimeUnit, GenSignalUnit, GenSignalDutyCycle) 
  Call ChnGenSignal("Sine", 1024, 1000, oChnSine40Hz, 40, 0.5*9.81, 0, 0, "s", oChnSine40Hz.UnitSymbol, 50)
  'Convert oChnSine40Hz from waveform to numeric
	If ProgramRevision => 2100 Then 
		Set oElementList =  ChnConvertWaveformToNumeric(oChnSine40Hz, False, "WfXRelative")
	Else
		Set oElementList =  WfChnToChn(oChnSine40Hz, False, "WfXRelative")
	End If
  Call oGrp.Channels.Remove(oElementList.Item(1).Name)
  
  'Add the two sine channels to create the acceleration channel
  Call ChnAdd(oChnSine3Hz, oChnSine40Hz, oChnY)
  Set oChnY.XRelation = oChnX
  oChnY.UnitSymbol = oChnSine40Hz.UnitSymbol
  
  'Delete the two sine channels
  Call oGrp.Channels.Remove(oChnSine3Hz.Name)
  Call oGrp.Channels.Remove(oChnSine40Hz.Name)
  
  Call UIAutoRefreshSet(bUIAutoRefresh): View.AutoRefresh = bViewAutoRefresh': Call View.Refresh()
End Sub 'SigGenAccelUpsPkg()

The last example demonstrated clearly how the DIAdem FFT (One Time Signal) calculation is able to identify the dominate frequencies in a signal of a known composition (3 Hz and 40 Hz sine waves). The next example will perform the same calculation on a signal with random vibration. Clear the Data Portal using the NAVIGATOR panel menu 'File', 'New'. Load the DIAdem example file 'FFT_Expl_1.TDM' located in the folder: 'C:\PROGRAM FILES\NATIONAL INSTRUMENTS\DIADEM ####\Examples\Data\'

From the ANALYSIS panel, choose the menu options 'Signal Analysis', 'FFT (One Time Signal)...'. Drag and drop the 'Oscillation' channel from the Data Portal to the dialog channel control labeled 'Signal channels:'. The channel control 'Time channel:' should be automatically assigned to '[1]/Time' because the XRelation is set for 'Oscillation', otherwise make the assignment manually. Configure the dialog options exactly as shown below. Click the 'Calculate' to perform the analysis, and then close the dialog.

Review the dominate frequencies identified by plotting the generated channels in a VIEW panel sheet. Activate the VIEW panel. In the Data Portal, select the 'Frequency' channel first, and then the 'AmplitudePeak' channel. Drag and drop the channels into the VIEW sheet center area. A popup menu will appear, choose the '2D Axis System' option. (help). Use the 2D Axis System toolbar 'Band Zoom' to zoom into the range of 0 to 40 Hz (help). Use the VIEW toolbar 'View Cursor' to see the values for the highest peak in the channel (help). The maximum amplitude is 1.69 mm/s^2 at 0.49 Hz.

RMS Amplitude

The quadratic integral mean value of an oscillation. This calculation is typically used to determine the RMS sound pressure from a sound vibration signal.

Power Spectrum

This is the square of the RMS amplitude. A typical application is the calculation of the RMS sound pressure from the measured sound vibration. See also Frequency Weighting (A-B-C Filtering)

Autospectrum

This is the square of the peak amplitude.

Power Spectral Density (PSD)

The calculated power spectrum is normalized to the frequency intervals (bins). As a result, the calculation is not sensitive to the source signal sample rate or duration. PSD spectra are not summed, they are integrated in order to retain the cumulative curve. A PSD is the ideal option for comparing spectra between one or more signals with different durations and/or sample rates. It is also a good choice when no finite number of dominate frequency components exist in the signal (random vibration). Many test standards will describe their vibration environment with a PSD.

In this tutorial, a DIAdem example vibration signal will be resampled to consist of 2.5x the sample rate and number of samples of the original signal. Then a FFT (One Time Signal) analysis will be performed on both channels to confirm that the results are the same, despite the fact that the sample rate and the number of samples (channel values) is different between the two signals.

Prepare the sample data for this tutorial be completing all of the steps from the Resampling tutorial, or simply run the script presented at the end of that tutorial. The Data Portal should appear as shown in the image below.

Activate the ANALYSIS panel and choose the menu options 'Signal Analysis', 'FFT (One Time Signal)...'. Configure the 'FFT with One Time Signal' dialog exactly as shown in the images below, including the options for the 'Window Functions', 'FFT Functions', and 'Time Intervals' tabs. IMPORTANT: In the 'Time Intervals' tab, toggle the options under 'Parameters to be entered' from what is currently selected, to another option in order to force the dialog to update the interval options. Before continuing, make sure the 'All' option for 'Parameters to be entered' is selected. Click the 'Calculate' button to generate the FFT PSD result channels. Click the 'Close' button to close the dialog.

Rename the channels as follows:

'Frequency' -> 'Vibration2525Hz_Freq'
'PowerSpectralDensity' -> 'Vibration2525Hz_PSD'
'Frequency1' -> 'Vibration6313Hz_Freq'
'PowerSpectralDensity1' -> 'Vibration6313Hz_PSD'

Visually compare the PSD results in a VIEW sheet 2D Axis System. Activate the VIEW panel and create a new layout with the 'File', 'New' menu options. Choose the 'Regular Worksheet Partitions' group bar and then the option 'Two Areas'.

In the Data Portal, select the channel 'Vibration2525Hz_Freq' first, and then the channel 'Vibration2525Hz_PSD'. Drag and drop them into the VIEW sheet upper area, and then choose the '2D Axis System' from the popup menu that appears. Use the '2D Axis System' toolbar option 'Band Zoom' to zoom in to the X axis range of 0 to 200 Hz.

In the Data Portal, select the channel 'Vibration6313Hz_Freq' first, and then the channel 'Vibration6313Hz_PSD'. Drag and drop them into the VIEW sheet lower area, and then choose the '2D Axis System' from the popup menu that appears. Use the '2D Axis System' toolbar option 'Band Zoom' to zoom in to the X axis range of 0 to 200 Hz. You can visually see that the two PSD results are very similar, despite the 2.5x difference in the sample rate and the number of samples between the two signals analyzed.

The VBScript below will replicate all of the prior manual steps.


' FFT (One Time Signal) with amplitude option 'Power Spectral Density' (PSD)

Call LogFileDel()
Dim oChnX1, oChnY1, oChnDelta, dSampleRateHz, oChnY2, oChnX2, oElementList
Dim oChnX1Freq, oChnY1PSD, oChnX2Freq, oChnY2PSD
Dim oChnFFT
Dim sPathDocuments, sPathData
sPathDocuments = ProgramDrv & "Examples\Documents\"
sPathData      = ProgramDrv & "Examples\Data\"
Call Data.Root.Clear()
Call DataFileLoadSel(sPathData & "Harmonic_Cursor.tdm","TDM","[1]/[1,2]","Load|ChnXYRelation")
Data.Root.ChannelGroups(1).Name = "FFT1_PSD"
Set oChnX1 = Data.GetChannel("FFT1_PSD/Time")
oChnX1.Name = "Time1"
Set oChnY1 = Data.GetChannel("FFT1_PSD/Vibration")
Set oChnY1.XRelation = oChnX1

If Not ChnIsEquidistant(oChnX1, True, "CheckAll") Then
  Call LogFileWrite("Rebuilding time channel '" & oChnX1.GetReference(eReferenceIndexName) & "' because it is not equidistant..")
  Call ChnLinGen(oChnX1, oChnX1.Values(1), oChnX1.Values(oChnX1.Size), oChnX1.Size, "s")
End If
If Not ChnIsEquidistant(oChnX1, True, "CheckAll") Then Call Err.Raise(65535,,"ERROR: Unable to rebuild non-equidistant channel '" & oChnX1.GetReference(eReferenceIndexName) & "'")

'Calculate the sample rate
Set oChnDelta = oChnX1.ChannelGroup.Channels.Add("TimeDelta",DataTypeChnFloat64)
Call ChnDeltaCalc(oChnX1, oChnDelta)
Call ChnStatisticsChannelCalc(oChnDelta, eStatsMedian, NoValue, NoValue, False, False, False, "NameName")
dSampleRateHz = 1/oChnDelta.Properties("Result~Statistics~Quantiles~Median").Value
Call oChnY1.ChannelGroup.Channels.Remove(oChnDelta.Name)
Call oChnY1.Properties.Add("SampleRateHz",dSampleRateHz,DataTypeFloat64)

'Create a new channel w/ 2.5x the sample rate of oChnY1
dSampleRateHz = 2.5*dSampleRateHz
Set oChnY2 = oChnX1.ChannelGroup.Channels.Add(oChnY1.Name & Str(Fix(dSampleRateHz)) & "Hz",DataTypeChnFloat64)
oChnY2.UnitSymbol = oChnY1.UnitSymbol
oChnY1.Name = oChnY1.Name & Str(Fix(oChnY1.Properties("SampleRateHz").Value)) & "Hz"

'Resample oChnY1 and output the result to oChnY2
Call ChnResampleFreqBased(oChnX1, oChnY1, oChnY2, dSampleRateHz, "Automatic", False, False, "Akima")
Call oChnY2.Properties.Add("SampleRateHz",dSampleRateHz,DataTypeFloat64)

'Convert oChnY2 from waveform to numeric
If ProgramRevision => 2100 Then 
	Set oElementList =  ChnConvertWaveformToNumeric(oChnY2, False, "WfXRelative")
Else
	Set oElementList =  WfChnToChn(oChnY2, False, "WfXRelative")
End If
Set oChnX2 = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceIndexName))
oChnX2.Name = "Time2"
Call ChnValExpand(oChnX2)
Set oChnY2.XRelation = oChnX2

'oChnY2 has a different sample rate and duration (length) from oChnY1
Call LogFileWrite("Channel '" & oChnY1.GetReference(eReferenceIndexName) & "' sample rate: " & Str(oChnY1.Properties("SampleRateHz").Value,"AutoAdj") & " Hz")
Call LogFileWrite("Channel '" & oChnY1.GetReference(eReferenceIndexName) & "' # samples: " & Str(oChnY1.Size,"AutoAdj"))
Call LogFileWrite(vbTab)
Call LogFileWrite("Channel '" & oChnY2.GetReference(eReferenceIndexName) & "' sample rate: " & Str(oChnY2.Properties("SampleRateHz").Value,"AutoAdj") & " Hz")
Call LogFileWrite("Channel '" & oChnY2.GetReference(eReferenceIndexName) & "' # samples: " & Str(oChnY2.Size,"AutoAdj"))

'Execute FFT (One Time Signal) with PSD amplitude option on oChnX1/oChnY1
FFTIndexChn      = False
'----------- Window Functions -----------
FFTWndFct        = "Rectangle"
FFTWndPara       = 10
FFTWndChn        = oChnX1.GetReference(eReferenceIndexName)
FFTWndCorrectTyp = "No"
'------------ FFT Functions -------------
FFTCalc          = False
FFTAmpl          = True
FFTPhase         = False
FFTCepstrum      = False
FFTAmplType      = "PSD"
FFTAverageType   = "No"
FFTAmplExt       = "No"
FFTAmplFirst     = "Amplitude"
'------------ Time Intervals ------------
FFTIntervUser    = "all"
FFTIntervOverl   = 0
FFTNoV           = False
FFTIntervPara(1) = 1
FFTIntervPara(2) = oChnY1.Size
FFTIntervPara(3) = 1
'------------ Command -------------------
Set oElementList = ChnFFT1(oChnX1, oChnY1)
Set oChnX1Freq =  Data.GetChannel(oElementList.Item(1).GetReference(eReferenceIndexName))
oChnX1Freq.Name = oChnX1.Name & "_Freq"
Set oChnY1PSD =  Data.GetChannel(oElementList.Item(2).GetReference(eReferenceIndexName))
oChnY1PSD.Name = oChnY1.Name & "_PSD"


'Execute FFT (One Time Signal) with PSD amplitude option on oChnX2/oChnY2
FFTIndexChn      = False
'----------- Window Functions -----------
FFTWndFct        = "Rectangle"
FFTWndPara       = 10
FFTWndChn        = oChnX2.GetReference(eReferenceIndexName)
FFTWndCorrectTyp = "No"
'------------ FFT Functions -------------
FFTCalc          = False
FFTAmpl          = True
FFTPhase         = False
FFTCepstrum      = False
FFTAmplType      = "PSD"
FFTAverageType   = "No"
FFTAmplExt       = "No"
FFTAmplFirst     = "Amplitude"
'------------ Time Intervals ------------
FFTIntervUser    = "all"
FFTIntervOverl   = 0
FFTNoV           = False
FFTIntervPara(1) = 1
FFTIntervPara(2) = oChnY2.Size
FFTIntervPara(3) = 1
'------------ Command -------------------
Set oElementList = ChnFFT1(oChnX2, oChnY2)
Set oChnX2Freq =  Data.GetChannel(oElementList.Item(1).GetReference(eReferenceIndexName))
oChnX2Freq.Name = oChnX2.Name & "_Freq"
Set oChnY2PSD =  Data.GetChannel(oElementList.Item(2).GetReference(eReferenceIndexName))
oChnY2PSD.Name = oChnY2.Name & "_PSD"

'Plot the FFT PSD results in the VIEW panel as 2D Axis System
Dim oSheet, oAreaTop, oAreaBottom, o2DCurve, o2Dtbl
Call View.NewLayout
Set oSheet = View.ActiveSheet
Set oAreaTop = oSheet.ActiveArea: oAreaTop.Name = "Top": Set oAreaBottom = oAreaTop.SplitBottom("Bottom",-1)
oAreaTop.DisplayObjType = "CurveChart2D"
oAreaTop.DisplayObj.YScaling = "1 system [phys.]"   ' "1 system [phys.]"  "n systems [phys.]"  "n axes [phys.]"  
oAreaTop.DisplayObj.XScalingMode = "RangeFull"
Set o2DCurve = oAreaTop.DisplayObj.Curves2D.Add(oChnX1Freq.GetReference(eReferenceNameName),oChnY1PSD.GetReference(eReferenceNameName))
oSheet.Cursor.X1 = -5.0: oSheet.Cursor.X2 = +200.0
oAreaTop.DisplayObj.XScalingMode = "RangeZoom"
oSheet.Cursor.Type="Band"

oAreaBottom.DisplayObjType = "CurveChart2D"
oAreaBottom.DisplayObj.YScaling = "1 system [phys.]"   ' "1 system [phys.]"  "n systems [phys.]"  "n axes [phys.]"  
oAreaBottom.DisplayObj.XScalingMode = "RangeFull"
Set o2DCurve = oAreaBottom.DisplayObj.Curves2D.Add(oChnX2Freq.GetReference(eReferenceNameName),oChnY2PSD.GetReference(eReferenceNameName))
oSheet.Cursor.X1 = -5.0: oSheet.Cursor.X2 = +200.0
oAreaBottom.DisplayObj.XScalingMode = "RangeZoom"
oSheet.Cursor.Type="Band"

oSheet.Cursor.Type="Crosshair": oSheet.Cursor.Mode="arbitrary"
Call View.Refresh: Call WndShow("VIEW")

Third/Octave

This amplitude option will examine the volume from sound data in frequency intervals, not the exact frequency distribution in a signal. The third/octave analysis sums up the amplitude values in the FFT in standardized logarithmic frequency intervals. When DIAdem runs a third or an octave analysis, DIAdem checks the measurement signal for one or more thirds or octaves. DIAdem runs the third and octave analysis in stages while filtering and reducing the data. Reducing the data, leads DIAdem to three thirds or to one octave. When the lowest specified average frequency is reached, DIAdem ends the data reduction.

FFT (Two Time Signals)

When a forcing function (stimulation) is measured in addition to a response, then this analysis should be employed. With this calculation, the transfer function determines the relation of the stimulus to the response.

Coherence

DIAdem calculates the linear relation between two signals from the averaged cross spectrum and autospectrum of the signals. This option is only appropriate when the same measurement is repeated and is then overlaid with distortion signals.

Cross Spectrum

This calculation option is the complex product of two time signals transformed into the frequency domain. It represents the similarity of the signals in the frequency domain and corresponds with the cross correlation in the time domain.

Transfer Function

The transfer function calculation considers the two signals acquired simultaneously as the stimulus signal and response signal from a dynamic system. The stimulation signal is either noise with all frequencies, or an abrupt impulse/shock input such as a hammer impact.

Inverse FFT

This is the reverse operation of the 'FFT (One Time Signal)' calculation.

Full Spectrum FFT

This calculation executes various separate FFT analysis for the two vibration sensors on a rotating shaft, and connects the spectra to a complex FFT. Any DC bias is removed first from every input channel using 'AC/DC Coupling'. An example of the Full Spectrum FFT is can be found within the rotating shaft analysis), specifically here. WARNING: Always convert waveform channels to numeric before using this calculation from the ANALYSIS dialog 'Full Spectrum FFT'.

Shock Response Spectrum

The shock response spectrum (SRS) calculates and defines how a single degree-of-freedom system with different theoritical natural frequencies would respond to a shock. The calculated acceleration in the frequency domain will tell you what frequencies are dampening the input, and which are amplifying it.

The dialog options of pulse duration and time range specify which section of the measured acceleration signal to use as the stimulation. The pulse duration specifies a section defined from the signal start. The time range settings 'primary range', 'residual range', and 'complete range' refer to the pulse duration. If the pulse duration is 0, the complete acceleration signal is used.

The result type dialog options determine whether the shock response spectrum calculates the acceleration, the relative velocity, or the relative displacement from the acceleration signal in m/s2. The SRS is calculated in accordance with the ISO norm 18431-4:2007.

The algorithm that NI DIAdem uses to calculate the SRS per ISO-Norm 18431-4:2007 is named 'Ramp Invariant (Smallwood)'.

The signal analyzed by SRS should be centered about the the y-axis. If a DC bias exists, it should be removed prior to an SRS analysis.

Find, load, and run the NI DIAdem example script file 'ShockResponseSpectrum_Automated.vbs' located in the folder: 'C:\PROGRAM FILES\NATIONAL INSTRUMENTS\DIADEM ####\Examples\Data\'. The VBScript will calculate acceleration, velocity and displacement from the acceleration signal 'Pyro', with separate curves for the section of the source signal used as the stimulation.

The following manual calculation example will use the 'Shock Response Spectrum (SRS)' dialog to calculate the SRS of a signal as maximum absolute acceleration between 0 and 1 kHz. The input signal from 0 to 0.01 sec will be used as the stimulation. The frequency resolution will be set to 12 frequencies per octave, and a damping factor of 0.05 will be applied.

Activate the ANALYSIS panel and choose the menu options 'Signal Analysis', 'Shock Response Spectrum (SRS)...'. Configure the dialog exactly as shown in the image below. Click the 'Calculate' button to perform the analysis, and then close the dialog.

The 'Shock Response Spectrum (SRS)' will generate two numeric channels, 'SRSFrequency', and 'SRSAccelerationMaxiMax'. Plot these generated results in the VIEW panel. Activate the VIEW panel, create a new layout ('File','New'), and then from the group bar 'Regular Worksheet Partitions' and the option 'Two Areas'. Drag and drop the channel 'Pyro' from the Data Portal to the VIEW sheet upper area. Choose the popup box option '2D Axis System' option. In the Data Portal, select the channel 'SRSFrequency' first, and then the channel 'SRSAccelerationMaxiMax'. Drag and drop the channels from the Data Portal to the VIEW sheet lower area. Choose the popup box option '2D Axis System' option. Change the x-axis and y-axis scaling to logarithmic by right clicking on the lower 2D Axis System plot and choosing the menu option 'X-Axis' 'X-Axis [Log.]'. Right click on the lower 2D Axis System plot and choosing the menu option 'Y-Axis' 'Y-Axis [Log.]'.

The VBscript below will reproduce the prior manual commands.


' Shock Response Spectrum (SRS)

Dim sPathDocuments, sPathData
sPathDocuments = ProgramDrv & "Examples\Documents\"
sPathData      = ProgramDrv & "Examples\Data\"
Call Data.Root.Clear
Call DataFileLoad(sPathData & "ShockResponseSpectrum.tdm", "TDM", "Load|ChnXYRelation")

'Calculate the SRS of the 'Pyro' signal as maximum absolute acceleration from 0 to 1 kHz. 
'Include the input signal from 0 to 0.01 sec as the stimulation.
'Use 12 frequencies per octave (determines the frequency resolution)
'Use a damping factor of 0.05     SRS damping = 1 / 2*Q, where Q = quality factor
SRSRangeType = "All"                'The "Complete range" of the pulse duration (0 to 0.01 s)
                                    'time domain will be used for the stimulation. 
SRSAmplitudeType = "AmpMaxiMax"     'Shock response amplitude type of absolute maxima
SRSResultType = "Acceleration"      'Shock response result type of acceleration
SRSStartFrequency = 0
SRSEndFrequency = 1000              '1000 Hz or 1 kHz
SRSFreqPerOctave = 12               'Higher number = finer resolution / more narrow frequency spacing
SRSDamping = 0.05
SRSPulseDuration = 0.01             'Pulse duration from 0 to 0.01 s for the shock response

'ChnShockResponseSpectrum(XW, Y, ResultChannel, ResultChannel, SRSRangeType, SRSAmplitudeType, SRSResultType, SRSStartFrequency, SRSEndFrequency, SRSFreqPerOctave, SRSDamping, SRSPulseDuration) 
Call ChnShockResponseSpectrum("","[1]/Pyro","/SRSFrequency","/SRSAccelerationMaxiMax","All","AmpMaxiMax","Acceleration", 0, 1000, 12, 0.05, 0.01) 

'Plot the FFT PSD results in the VIEW panel as 2D Axis System
Dim oSheet, oAreaTop, oAreaBottom, o2DCurve, o2Dtbl
Call View.NewLayout
Set oSheet = View.ActiveSheet
Set oAreaTop = oSheet.ActiveArea: oAreaTop.Name = "Top": Set oAreaBottom = oAreaTop.SplitBottom("Bottom",-1)
oAreaTop.DisplayObjType = "CurveChart2D"
oAreaTop.DisplayObj.YScaling = "1 system [phys.]"   ' "1 system [phys.]"  "n systems [phys.]"  "n axes [phys.]"  
oAreaTop.DisplayObj.XScalingMode = "RangeFull"
Set o2DCurve = oAreaTop.DisplayObj.Curves2D.Add("",Data.GetChannel("[1]/Pyro").GetReference(eReferenceNameName))
oSheet.Cursor.X1 = 0.0: oSheet.Cursor.X2 = 0.01
oSheet.Cursor.Type="Band"

oAreaBottom.DisplayObjType = "CurveChart2D"
oAreaBottom.DisplayObj.XScalingMode = "RangeFull"
Set o2DCurve = oAreaBottom.DisplayObj.Curves2D.Add(Data.GetChannel("[1]/SRSFrequency").GetReference(eReferenceNameName),Data.GetChannel("[1]/SRSAccelerationMaxiMax").GetReference(eReferenceNameName))
oAreaBottom.DisplayObj.XScalingType = "logarithmic"
oAreaBottom.DisplayObj.YScaling = "1 system [log.]"

Call View.Refresh(): Call WndShow("VIEW")

Other Related Calculations

AC/DC Coupling

Remove the DC bias from an AC signal using the DIAdem calculation AC/DC Coupling.

Clear the Data Portal using the NAVIGATOR panel menu 'File', 'New'. Load the DIAdem example file 'FFT_Expl_1.TDM' located in the folder: 'C:\PROGRAM FILES\NATIONAL INSTRUMENTS\DIADEM ####\Examples\Data\'

Create two channels from the source channel 'Oscillation', one channel with a + 5 mm/s offset, and the other with a - 5 mm/s offset. From the DIAdem ANALYSIS panel, choose the menu options 'Basic', 'Offset Correction...'. In the 'Offset Correction' dialog, drag and drop the 'Oscillation' channel from the Data Portal to the dialog channel input control labeled 'Channel:'. Under the 'Offset' options, choose the 'Add any offset' and enter a value of '5' for the 'Value [mm/s]:'. Make sure the checkbox 'Store result in original channel' is not checked. Click the 'Calculate' button to create the new channel with the offset. Click the 'Close' button to close the dialog. In the Data Portal, rename the 'Offset' channel to 'Offset_Plus_5'.

From the DIAdem ANALYSIS panel, choose the menu options 'Basic', 'Scale'. In the 'Scale' dialog, drag and drop the 'Oscillation' channel from the Data Portal to the dialog channel input control labeled 'Channel:'. Set the 'Factor' to 1, and the 'Offset' to -5. Make sure the checkbox 'Store result in original channel' is not checked. Click the 'Calculate' button to create the new channel with the offset. Click the 'Close' button to close the dialog. Rename the channel 'LinearScaled' to 'Offset_Minus_5'.

The Data Portal now contains two new channels, one with a positive offset of 5 mm/s, and the other with a negative offset of 5 mm/s.

From the DIAdem ANALYSIS panel, choose the menu options 'Signal Analysis', 'AC/DC Coupling'. Drag and drop the 'Offset_Plus_5' channel from the Data Portal to the 'AC/DC Coupling' dialog channel control labeled 'Channel:'. Set the 'Window type:' to 'Rectangle'. Make sure the checkbox 'Store result in original channel' is not checked. Click the 'Calculate' button to create the new channel with the offset removed, as shown in the 'Result data' preview 2D axis plot.

Repeat the process for the 'Offset_Minus_5' channel. Click the 'Close' button to close the dialog when finished.

Rename the channel 'ACCoupled' to 'ACCoupled_Plus_5'. Rename the channel 'ACCoupled1' to 'ACCoupled_Minus_5'. Activate the REPORT panel. Choose the menu options 'File', 'New' to clear the report area. Load the report layout 'AC-DC-Coupling.TDR' from the folder: 'C:\PROGRAM FILES\NATIONAL INSTRUMENTS\DIADEM ####\Examples\Documents\' or ''C:\Users\Public\Documents\National Instruments\DIAdem ####\Documents\' (location varies by DIAdem version). Refresh the report by either pressing the 'F5' key, or access the REPORT panel menu 'View', 'Refresh'. The report shows the removal of the +/- 5 mm/s bias from each signal.

The script below derived from the DIAdem example script file 'AC-DC-Coupling.VBS will replicate the actions above.


Dim sPathDocuments, sPathData
sPathDocuments = ProgramDrv & "Examples\Documents\"
sPathData      = ProgramDrv & "Examples\Data\"

Call Data.Root.Clear()
Call DataFileLoad(sPathData & "FFT_Expl_1.TDM", "TDM", "Load|ChnXYRelation") 

' Create a new channel with a positive 5 mm/s DC bias
Call ChnOffset("[1]/Oscillation","/Offset_Plus_5",5,"free offset")

' Create a new channel with a negative 5 mm/s DC bias
Call ChnOffset("[1]/Oscillation","/Offset_Minus_5",-5,"free offset")

' Decouple new offset channels
Call ChnACDCCoupling("[1]/Offset_Plus_5","/ACCoupled_Plus_5","Rectangle")
Call ChnACDCCoupling("[1]/Offset_Minus_5","/ACCoupled_Minus_5","Rectangle")

Call Report.LoadLayout(sPathDocuments & "AC-DC-Coupling.TDR")
Call Report.Refresh

Characterize Oscillation & SINAD Analysis

Determine the frequency with the largest amplitude and the phase of that frequency. Calculate the ratio of the total signal power to the distortion signal power in decibels.

Clear the Data Portal using the NAVIGATOR panel menu 'File', 'New'. Selective load the channels 'Data/Time' and 'Data/Measurement Data' from the file 'WaveCharacteristics.tdm' located in the folder: 'C:\PROGRAM FILES\NATIONAL INSTRUMENTS\DIADEM ####\Examples\Data\'. (For help with selective channel loading, see selective file loading example).

Identify the fundamental frequency and phase angle. Activate the ANALYSIS panel and choose the menu options 'Signal Analysis', 'Characterize Oscillation...'. Drag and drop the 'Time' and 'Measurement Data' channels to the dialog channel controls as shown in the image below. Set the 'Search criteria' to 'Browse entire frequency domain'. The results are immediately shown in the bottom right of the dialog (frequency = 60 Hz, amplitude = 5.0, phase = 240 degrees). Click the 'Calculate' button to add those calculated values as properties to the channel 'Measurement Data'. Click the 'Close' button to close the dialog.

In the Data Portal, select the channel 'Measurement Data' and then review the custom properties added by 'Characterize Oscillation'.

Calculate the harmonic distortion. Activate the ANALYSIS panel and choose the menu options 'Signal Analysis', 'SINAD Analysis...'. Drag and drop the 'Time' and 'Measurement Data' channels to the dialog channel controls as shown in the image below. Note that the results are immediately displayed in the bottom right of the dialog. Click the 'Calculate' button to add those calculated values as properties to the channel 'Measurement Data'. Click the 'Close' button to close the dialog.

The calculations 'Characterize Oscillation' and 'SINAD Analysis' don't leave behind any generated channels from the FFT analysis. If you need those FFT channels (frequency & amplitude), then you need to perform the 'FFT (One Time Signal)' analysis.

The script below derived from the NI DIAdem example script file 'C:\PROGRAM FILES\NATIONAL INSTRUMENTS\DIADEM ####\Examples\Documents\WaveCharacteristics.vbs' will replicate the prior manual commands.


' DIAdem example:  Characteristics of an oscillation

Call LogFileDel()
Dim oChnX, oChnY, oChnFrequency, oChnAmplitude, oElementList
Dim sPathDocuments, sPathData
sPathDocuments = ProgramDrv & "\Examples\Documents\"
sPathData      = ProgramDrv & "\Examples\Data\"
Call Data.Root.Clear()
Call DataFileLoadSel(sPathData & "WaveCharacteristics.TDM", "TDM", "[1]/[1,2]", "Load|ChnXYRelation")
Set oChnX = Data.GetChannel("Data/Time")
Set oChnY = Data.GetChannel("Data/Measurement Data")
Set oChnY.XRelation = oChnX
oChnY.UnitSymbol = "V"

'Calculate the FFT peak amplitude  (dialog is 'FFT (One Time Signal)')
FFTIndexChn      = False
'----------- Window Functions -----------
FFTWndFct        = "Rectangle"
FFTWndPara       = 10
FFTWndChn        = oChnX.GetReference(eReferenceIndexName)
FFTWndCorrectTyp = "No"
'------------ FFT Functions -------------
FFTCalc          = False
FFTAmpl          = True
FFTPhase         = False
FFTCepstrum      = False
FFTAmplType      = "Ampl.Peak"
FFTAverageType   = "No"
FFTAmplExt       = "No"
FFTAmplFirst     = "Amplitude"
'------------ Time Intervals ------------
FFTIntervUser    = "NumberStartOverl"
FFTIntervOverl   = 0
FFTNoV           = False
FFTIntervPara(1) = 1
FFTIntervPara(2) = oChnY.Size
FFTIntervPara(3) = 1
Set oElementList = ChnFFT1(oChnX, oChnY)
Set oChnFrequency = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceIndexname))
Set oChnAmplitude = Data.GetChannel(oElementList.Item(2).GetReference(eReferenceIndexname))

Call Report.LoadLayout(sPathDocuments & "WaveCharacteristics.TDR")

'Get the fundamental frequency (dialog is 'Characterize Oscillation')
Call ChnSingleToneExtract(oChnX,oChnY,0,10)
Call LogFileWrite("Max amplitude of " & Str(Data.GetChannel("Data/Measurement Data").Properties("Result~SingleTone~Amplitude").Value,"AutoAdj") & " " & Data.GetChannel("Data/Measurement Data").UnitSymbol & " at " & Str(Data.GetChannel("Data/Measurement Data").Properties("Result~SingleTone~Frequency").Value,"AutoAdj") & " Hz with phase of " & Str(Data.GetChannel("Data/Measurement Data").Properties("Result~SingleTone~Phase").Value,"AutoAdj") & " degrees")
' Max amplitude of 5.00 V at 60.00 Hz with phase of 240.35 degrees

'Calculate the harmonic distortion  (dialog is 'SINAD Analysis')
Call ChnSINAD(oChnX,oChnY,0,10)
Call LogFileWrite("Signal / noise ratio (SINAD): " & Str(oChnY.Properties("Result~SINAD~Value").Value,"AutoAdj") & " dB")
Call LogFileWrite("Fundamental frequency:= " & Str(oChnY.Properties("Result~SINAD~DetectedFrequency").Value,"AutoAdj") & " Hz")
Call LogFileWrite("Harmonic Distortion: " & Str(oChnY.Properties("Result~SINAD~THDPlusNoise").Value,"AutoAdj"))
'  Signal / noise ratio (SINAD): 3.93 dB
'  Fundamental frequency:= 60.00 Hz
'  Harmonic Distortion: 0.405

Call Report.Refresh

Rotating Shaft Analysis

A complete analyis of rotating shaft vibration, including the generation of an interactive VIEW panel is available via the DIAdem help example 'Vibration Data Analysis with Parallel Processing'. This example demonstrates the following:

Calculate full spectrum FFT for accelerometers positioned perpendicular to positions on a shaft.
Analyze the movement of shaft center.
Evaluate tachometer pulse signals measured by a sensor on a shaft.
Calculate the amplitude and phases for each order for a Bode diagram.

Find, load, and run the NI DIAdem example script file 'C:\PROGRAM FILES\NATIONAL INSTRUMENTS\DIADEM ####\Examples\Documents\RotatingShaftAnalysis.vbs'. NOTE: This example requires that the DIAdem example data folder is indexed by My DataFinder.

The manual use of the individual DIAdem calculations 'Full Spectrum FFT', 'Shaft Centerline', 'Pulse Detection', and 'Order Analysis for Bode Display' are each shown below.

Full Spectrum FFT

This calculation executes various separate FFT analysis for the two vibration sensors on a rotating shaft, and connects the spectra to a complex FFT. Any DC bias is removed first from every input channel using 'AC/DC Coupling'. WARNING: Always convert waveform channels to numeric before using this calculation from the ANALYSIS dialog 'Full Spectrum FFT'.

Clear the Data Portal. Load the file 'RotatingShaftAnalysis_000.tdm' located in the folder 'C:\Program Files\National Instruments\DIAdem ####\Examples\Data\Sound & Vibration\'.

Convert the channels 'Pulse', Sensor_X', and 'Sensor_Y' from type waveform to numeric (waveform to numeric channel conversion example). Convert the 'Time' channel from implicit to explicit by using the 'Expand Channel' Data Portal option. Set the XRelation (XY-channels) for the channels 'Pulse', Sensor_X', and 'Sensor_Y' by using the 'Channel Functions' menu option 'Channels <-> XY-Channels' option.

Access the ANALYSIS panel menu 'Signal Analysis', 'Full Spectrum FFT...'. Configure the 'Full Spectrum FFT' dialog as shown below, including both the 'Window Functions' and the 'Time Intervals' tab options. &Nbsp; Click the 'Calculate' button to perform the calculation, and then close the dialog when finished.

A new waveform channel named 'FullSpectrum' is created by the 'Full Spectrum FFT' calculation. Plot the channel 'FullSpectrum' in the VIEW panel. Activate the VIEW panel, create a new layout ('File','New'), and then from the group bar 'Regular Worksheet Partitions' and the option 'Two Areas'. Drag and drop the channel 'FullSpectrum' from the Data Portal to the VIEW sheet upper area. Choose the popup box option '2D Axis System' option. Use the area toolbar 'Band Zoom' option to zoom into the area between approximately X = -400 and +400 Hz.

The signal is very noisy. Filter the signal using a 'Savitzky-Golay Filter', creating a new filtered channel. When finished, drag and drop the filtered channel named 'FilteredSignal' to the VIEW lower sheet and choose the '2D Axis System' option.

The signal is still noisy and will not work well with the 'Find Peaks' ANALYSIS tool. Filter the channel 'FilteredSignal' again, this time using the 'Smooth' filter. From the ANALYSIS panel, choose the menu 'Curve Fitting', 'Smooth...'. Configure the 'Smooth' dialog as shown below and then click the 'Calculate' button. Close the dialog.

Use the area toolbar 'Band Zoom' option to zoom into the area between approximately X = -400 and +400 Hz. Using the VIEW toolbar 'Maximum Values Cursor', identify the dominate frequencies of +240, -231, and 0.5 Hz.

Use the 'Find Peaks' ANALYSIS tool to identify the three dominate frequencies in the channel named 'FilteredSignal'. Activate the ANALYSIS panel and choose the menu options 'Channel Functions', 'Find Peaks'. Configure the 'Find Peaks' dialog as shown below and then click the 'Calculate' button. Close the dialog when finished.

The 'Find Peaks' ANALYSIS tool will create two new channels named 'PeakX', and 'PeakY'. If you look at these channels as a Channel Table in a VIEW sheet area, you will see that they contain the X (PeakX), and Y (PeakY) values corresponding to the three peak values from the channel 'FilteredSignal'. These three X/Y pairs are the dominate frequencies identified by the Full Spectrum FFT calculation. In the Data Portal, select the 'PeakX' channel and then the 'PeakY' channel. Drag and drop these channels into the VIEW sheet lower area where the channel 'FilteredSignal' is currently plotted in a 2D Axis System. Right click on the 2D Axis System and choose the 'Settings...' menu option. In the curve list, change the color for the No. 2 curve to 'No Color'. Then to the right of that list, click the '...' button under 'Properties'. Click on the 'Markers' tab and configure the markers as shown below. Click on the 'Labels' tab and configure the labels as shown below. Click the 'OK' button when finished to close the 'Curve Properties' dialog, and then again to close the '2D Axis System' dialog.

The script below will replicate the prior manual commands.


' Rotating Shaft Analysis - Full Spectrum FFT

'Performs a 'Full Spectrum FFT' on a signal. 
'Filters the channel result with Savitzky-Golay and Smooth filter.
'Identifies the three dominate frequencies using 'Find Peaks'.
'Plots the channels to a VIEW sheet. 

Call LogFileDel()
Dim oChnSensorX, oChnSensorY, oChnPulse, oChnTime, oElementList, oChnFFTX, oChnFFTY, oChnFFTYfil
Dim oChnPeakX, oChnPeakY, o2Dtbl
Dim sPathDocuments, sPathData
sPathDocuments = ProgramDrv & "Examples\Documents\"
sPathData      = ProgramDrv & "Examples\Data\Sound & Vibration\"
Call Data.Root.Clear()
Call DataFileLoad(sPathData & "RotatingShaftAnalysis_000.tdm", "TDM", "Load|ChnXYRelation") 
Set oChnPulse = Data.GetChannel("[1]/Pulse")
Set oChnSensorX = Data.GetChannel("[1]/Sensor_X")
Set oChnSensorY = Data.GetChannel("[1]/Sensor_Y")

'Convert the waveform channels to numeric
'Note: Not necessary for ChnFullSpectrum() function, only the Full Spectrum FFT dialog.
Set oElementList = Data.CreateElementList()
Call oElementList.Add(oChnPulse)
Call oElementList.Add(oChnSensorX)
Call oElementList.Add(oChnSensorY)
If ProgramRevision => 2100 Then 
	Set oElementList =  ChnConvertWaveformToNumeric(oElementList, False, "WfXRelative")
Else
	Set oElementList =  WfChnToChn(oElementList, False, "WfXRelative")
End If
Set oChnTime = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceIndexName))
'Convert the time channel from read-only implicit to explicit
Call ChnValExpand(oChnTime)
'Assign the XRelation (Channels <-> XY Channels)
Set oChnPulse.XRelation = oChnTime
Set oChnSensorX.XRelation = oChnTime
Set oChnSensorY.XRelation = oChnTime

Set oElementList = ChnFullSpectrum(oChnTime, oChnSensorX, oChnSensorY, "Rectangle", "No", "NoOfIntervals", 1, 20000)
Set oChnFFTY = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceIndexName))

'Convert waveform channel to numeric
If ProgramRevision => 2100 Then 
	Set oElementList =  ChnConvertWaveformToNumeric(oChnFFTY, False, "WfXRelative")
Else
	Set oElementList =  WfChnToChn(oChnFFTY, False, "WfXRelative")
End If
Set oChnFFTX = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceIndexName))
'Convert the time channel from read-only implicit to explicit
Call ChnValExpand(oChnFFTX)
'Assign the XRelation (Channels <-> XY Channels)
Set oChnFFTY.XRelation = oChnFFTX

'Filter the channel 'FullSpectrum' with Savitzky-Golay filter, creating a new channel 'FullSpectrum_FIL'
Set oChnFFTYfil = oChnFFTY.ChannelGroup.Channels.Add(oChnFFTY.Name & "_FIL", DataTypeChnFloat64)
Call ChnSavitzkyGolayFilter(oChnFFTY, oChnFFTYfil, 1, 12)
Set oChnFFTYfil.XRelation = oChnFFTX

'Filter channel 'FullSpectrum_FIL' using the Smooth filter
Call ChnSmooth(oChnFFTYfil, oChnFFTYfil, 12, "maxNumber", "byMeanValue")

'Compare the channels in the VIEW panel as a 2D Axis System plot
Call View.NewLayout()
Dim oSheet, oAreaTop, oAreaCenter, oAreaBottom, o2DCurve
Set oSheet = View.ActiveSheet
Set oAreaTop = oSheet.ActiveArea
oAreaTop.Name = "Top"
Set oAreaBottom = oAreaTop.SplitBottom("BottomArea",0.33)
Set oAreaCenter = oAreaTop.SplitBottom("CenterArea",-1)

'Find the three peak values in oChnFFTYfil using 'Calculate Peaks'
Set oChnPeakX = oChnFFTYfil.ChannelGroup.Channels.Add("PeakX",DataTypeChnFloat64)
Set oChnPeakY = oChnFFTYfil.ChannelGroup.Channels.Add("PeakY",DataTypeChnFloat64)
Call ChnPeakFind(oChnFFTX, oChnFFTYfil, oChnPeakX, oChnPeakY, 3, "Max.Peaks", "Amplitude")

'Plot the 'FullSpectrum' channel to the VIEW sheet top area
oAreaTop.DisplayObjType = "CurveChart2D"   
' "1 system [phys.]"  "n systems [phys.]"  "n axes [phys.]"  
oAreaTop.DisplayObj.YScaling = "1 system [phys.]"
Set o2DCurve = oAreaTop.DisplayObj.Curves2D.Add(oChnFFTX.GetReference(eRefTypeIndexName), oChnFFTY.GetReference(eRefTypeIndexName))
oSheet.Cursor.X1 = -400.0: oSheet.Cursor.X2 = +400.0
oAreaTop.DisplayObj.XScalingMode = "RangeZoom"
oSheet.Cursor.Type="Band"

'Plot the 'FullSpectrum_FIL' channel to the VIEW sheet center area
oAreaCenter.DisplayObjType = "CurveChart2D"   
' "1 system [phys.]"  "n systems [phys.]"  "n axes [phys.]"  
oAreaCenter.DisplayObj.YScaling = "1 system [phys.]"
Set o2DCurve = oAreaCenter.DisplayObj.Curves2D.Add(oChnFFTX.GetReference(eRefTypeIndexName), oChnFFTYfil.GetReference(eRefTypeIndexName))
oSheet.Cursor.X1 = -400.0: oSheet.Cursor.X2 = +400.0
oAreaCenter.DisplayObj.XScalingMode = "RangeZoom"
oSheet.Cursor.Type="Band"
'Add the PeakX and PeakY channels to the 2D Axis System
Set o2DCurve = oAreaCenter.DisplayObj.Curves2D.Add(oChnPeakX.GetReference(eRefTypeIndexName), oChnPeakY.GetReference(eRefTypeIndexName))
o2DCurve.Color = ""
o2DCurve.MarkerType = "square"
o2DCurve.MarkerType                 = "square"
o2DCurve.MarkerColorAuto            = false
o2DCurve.MarkerColor                = "blue"
o2DCurve.MarkerColorRGB             = 0
o2DCurve.MarkerFillColorAuto        = false
o2DCurve.MarkerFillColor            = ""
o2DCurve.MarkerFillColorRGB         = 0
o2DCurve.MarkerSize                 = 1
o2DCurve.MarkerAtBegin              = false
o2DCurve.MarkerAtEnd                = false
o2DCurve.MarkerFrequencyMode        = "CalcNPoint"
o2DCurve.MarkerIntervalPoints       = 1
o2DCurve.MarkerIntervalLength       = 10
o2DCurve.MarkerLineWidth            = "0.5"
'
o2DCurve.Type                       = "Line"
o2DCurve.LabelChannelName           = "[1]/PeakX"
o2DCurve.LabelIndexChannelName      = ""
o2DCurve.LabelChannelOrientation    = "automatic"
o2DCurve.LabelMode                  = eVIEWLabelModeChannel
o2DCurve.LabelAtBegin               = false
o2DCurve.LabelAtEnd                 = false
o2DCurve.LabelText                  = ""
o2DCurve.LabelIntervalPoints        = 1
o2DCurve.LabelIntervalLength        = 0
o2DCurve.LabelRepetitionMode        = eVIEWLabelRepetitionEveryPoint
o2DCurve.LabelColorAuto             = false
o2DCurve.LabelColor                 = "blue"
o2DCurve.LabelColorRGB              = 0
o2DCurve.Name                       = "Curve2"
o2DCurve.TagStored                  = ""

'Zoom in to X = -400 to +400
oSheet.Cursor.X1 = -400.0: oSheet.Cursor.X2 = +400.0
oAreaCenter.DisplayObj.XScalingMode = "RangeZoom"
oSheet.Cursor.Type="Band"

'Show the channels PeakX and PeakY in the lower VIEW sheet area as a channel table
oAreaBottom.DisplayObjType = "ChannelTable"   
'oAreaBottom.DisplayObj.IndexColumnWidth = 60
Set o2Dtbl = oAreaBottom.DisplayObj.Columns.Add(oChnPeakX.GetReference(eReferenceNameName))
'o2Dtbl.Width = 60
Set o2Dtbl = oAreaBottom.DisplayObj.Columns.Add(oChnPeakY.GetReference(eReferenceNameName))

oSheet.Cursor.Type="Crosshair": oSheet.Cursor.Mode="arbitrary"
Call View.Refresh(): Call WndShow("VIEW")

Shaft Centerline

The DIAdem calculation 'Shaft Centerline' calculation should be used to determine the movement of the shaft center in the bearing box (imbalance), and if the bearing clearance is critical.

Clear the Data Portal. Load the file 'RotatingShaftAnalsis_000.tdm' located in the folder 'C:\Program Files\National Instruments\DIAdem ####\Examples\Data\Sound & Vibration\'. Note that the channels 'Sensor_X' and 'Sensor_Y' are waveform channels.

From the DIAdem ANALYSIS panel, choose the menu 'Signal Analysis' and the option 'Shaft Centerline...'. Assign the 'Sensor_X' and 'Sensor'Y' channels from the Data Portal to the dialog to the 'Shaft Centerline' dialog as shown below. Configure the 'Shaft Centerline' dialog tabs 'Reference Point' and 'Time Intervals' as shown below, and then click the 'Calculate' button. Click the 'Close' button to close the dialog.

The dialog 'Shaft Centerline' will create two new channels named 'ShaftCenterlineX', and 'ShaftCenterlineY'.

The script below will replicate the manual commands executed in this tutorial.


' Shaft Centerline

Call LogFileDel()
Dim oChnSensorX, oChnSensorY, oChnPulse, oChnShaftCenterlineX, oChnShaftCenterlineY
Dim oChnPeakX, oChnPeakY, o2Dtbl
Dim sPathDocuments, sPathData
sPathDocuments = ProgramDrv & "Examples\Documents\"
sPathData      = ProgramDrv & "Examples\Data\Sound & Vibration\"
Call Data.Root.Clear()
Call DataFileLoad(sPathData & "RotatingShaftAnalysis_000.tdm", "TDM", "Load|ChnXYRelation") 
Set oChnPulse = Data.GetChannel("[1]/Pulse")
Set oChnSensorX = Data.GetChannel("[1]/Sensor_X")
Set oChnSensorY = Data.GetChannel("[1]/Sensor_Y")
Set oChnShaftCenterlineX = oChnPulse.ChannelGroup.Channels.Add("ShaftCenterlineX",DataTypeChnFloat64)
Set oChnShaftCenterlineY = oChnPulse.ChannelGroup.Channels.Add("ShaftCenterlineY",DataTypeChnFloat64)

ShaftCenterlineGapRefX = 0
ShaftCenterlineGapRefY = 0
ShaftCenterlineIntervalType = "IntervalLength"
ShaftCenterlineNoOfIntervals = 20000
ShaftCenterlineIntervalLength = 1
'------------ Command -------------------
Call ChnShaftCenterline(oChnSensorX, oChnSensorY, oChnShaftCenterlineX, oChnShaftCenterlineY, 0, 0, "IntervalLength", 20000, 1)

Pulse Detection

Use 'Pulse Detection' to analyze a tachometer signal measured on a shaft to get the corrected time points of the pulse.

This tutorial is a continuation from the Shaft Centerline tutorial. You can quickly replicate the Data Portal contents generated from that tutorial by running the script at the end of that tutorial. Note that the channel 'Sensor_X' is a waveform channel, and 'PulseStartTime' is a numeric channel.

From the DIAdem analysis panel, choose the menu 'Signal Analysis' and the menu option 'Pulse Detection'. Configure the 'Pulse Detection' dialog as shown below and then click the 'Calculate' button.

Configure the 'Pulse Detection' dialog as shown below and then click the 'Calculate' button. Close the dialog.

The script below will replicate the manual commands executed in this tutorial.


' Pulse Detection

Call LogFileDel()
Dim oChnSensorX, oChnSensorY, oChnPulse, oChnShaftCenterlineX, oChnShaftCenterlineY, oElementList
Dim oChnPulseStartTime, oChnPulseDetectedRevolution
Dim oChnPeakX, oChnPeakY, o2Dtbl
Dim sPathDocuments, sPathData
sPathDocuments = ProgramDrv & "Examples\Documents\"
sPathData      = ProgramDrv & "Examples\Data\Sound & Vibration\"
Call Data.Root.Clear()
Call DataFileLoad(sPathData & "RotatingShaftAnalysis_000.tdm", "TDM", "Load|ChnXYRelation") 
Set oChnPulse = Data.GetChannel("[1]/Pulse")
Set oChnSensorX = Data.GetChannel("[1]/Sensor_X")
Set oChnSensorY = Data.GetChannel("[1]/Sensor_Y")
Set oChnShaftCenterlineX = oChnPulse.ChannelGroup.Channels.Add("ShaftCenterlineX",DataTypeChnFloat64)
Set oChnShaftCenterlineY = oChnPulse.ChannelGroup.Channels.Add("ShaftCenterlineY",DataTypeChnFloat64)

ShaftCenterlineGapRefX = 0
ShaftCenterlineGapRefY = 0
ShaftCenterlineIntervalType = "IntervalLength"
ShaftCenterlineNoOfIntervals = 20000
ShaftCenterlineIntervalLength = 1
'------------ Command -------------------
Call ChnShaftCenterline(oChnSensorX, oChnSensorY, oChnShaftCenterlineX, oChnShaftCenterlineY, 0, 0, "IntervalLength", 20000, 1)


' Pulse Detection - pulse start time
PulseDetResultType = "PulseStartTime"
PulseDetThresholdType = "Absolute"
PulseDetThresholdValue = 1
PulseDetPulseRevolution = 1
PulseDetHysteresisType = "Absolute"
PulseDetHysteresisValue = 0
PulseDetPulseWidth = 1
PulseDetSlope    = "Rising"
PulseDetInterpolMissValues = 0
'------------ Command -------------------
Set oElementList = ChnPulseDetection("", oChnPulse, "PulseStartTime", "Absolute", 1, 1, "Absolute", 0, 1, "Rising", 0)
Call LogFileWrite("New result channel '" & oElementList.Item(1).GetReference(eReferenceNameName) & "'")
Set oChnPulseStartTime = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceNameName))

' Pulse Detection - RPM
PulseDetResultType = "PulseDetectedRevolution"
PulseDetThresholdType = "Absolute"
PulseDetThresholdValue = 1
PulseDetPulseRevolution = 1
PulseDetHysteresisType = "Absolute"
PulseDetHysteresisValue = 0
PulseDetPulseWidth = 1
PulseDetSlope    = "Rising"
PulseDetInterpolMissValues = 0
'------------ Command -------------------
Set oElementList = ChnPulseDetection("", oChnPulse, "PulseDetectedRevolution", "Absolute", 1, 1, "Absolute", 0, 1, "Rising", 0)
Call LogFileWrite("New result channel '" & oElementList.Item(1).GetReference(eReferenceNameName) & "'")
Set oChnPulseDetectedRevolution = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceNameName))

Order Analysis for Bode Display

This tutorial requires channels created by the prior tutorial 'Pulse Detection'.

From the DIAdem analysis panel, choose the menu 'Signal Analysis' and the menu option 'Order Analysis for Bode Display'. Configure the 'Order Analysis for Bode Display' dialog as shown below and then click the 'Calculate' button. Assign the channel 'Sensor_Y' to the 'Order Analysis for Bode Display' dialog channel input control named 'Signal channels:' and then click the 'Calculate' once again. Close the dialog when finished.

At this point, one file out of 101 has been manually processed. For the most part, the channel created by the 'Order Analysis for Bode Display' dialog contain a single value that would need to be joined with the same from all of the other files in order to provide a complete data set for the VIEW panel configured by the example script.

The script below will replicate the manual commands executed in this tutorial.


Call LogFileDel()
Dim oChnSensorX, oChnSensorY, oChnPulse, oChnShaftCenterlineX, oChnShaftCenterlineY, oElementList
Dim oChnPulseStartTime, oChnPulseDetectedRevolution, i, oArea, o2Dtbl
Dim sPathDocuments, sPathData
sPathDocuments = ProgramDrv & "Examples\Documents\"
sPathData      = ProgramDrv & "Examples\Data\Sound & Vibration\"
Call Data.Root.Clear()
Call DataFileLoad(sPathData & "RotatingShaftAnalysis_000.tdm", "TDM", "Load|ChnXYRelation") 
Set oChnPulse = Data.GetChannel("[1]/Pulse")
Set oChnSensorX = Data.GetChannel("[1]/Sensor_X")
Set oChnSensorY = Data.GetChannel("[1]/Sensor_Y")
Set oChnShaftCenterlineX = oChnPulse.ChannelGroup.Channels.Add("ShaftCenterlineX",DataTypeChnFloat64)
Set oChnShaftCenterlineY = oChnPulse.ChannelGroup.Channels.Add("ShaftCenterlineY",DataTypeChnFloat64)

ShaftCenterlineGapRefX = 0
ShaftCenterlineGapRefY = 0
ShaftCenterlineIntervalType = "IntervalLength"
ShaftCenterlineNoOfIntervals = 20000
ShaftCenterlineIntervalLength = 1
'------------ Command -------------------
Call ChnShaftCenterline(oChnSensorX, oChnSensorY, oChnShaftCenterlineX, oChnShaftCenterlineY, 0, 0, "IntervalLength", 20000, 1)

' Pulse Detection - pulse start time
PulseDetResultType = "PulseStartTime"
PulseDetThresholdType = "Absolute"
PulseDetThresholdValue = 1
PulseDetPulseRevolution = 1
PulseDetHysteresisType = "Absolute"
PulseDetHysteresisValue = 0
PulseDetPulseWidth = 1
PulseDetSlope    = "Rising"
PulseDetInterpolMissValues = 0
'------------ Command -------------------
Set oElementList = ChnPulseDetection("", oChnPulse, "PulseStartTime", "Absolute", 1, 1, "Absolute", 0, 1, "Rising", 0)
Call LogFileWrite("New result channel '" & oElementList.Item(1).GetReference(eReferenceNameName) & "'")
Set oChnPulseStartTime = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceNameName))

' Pulse Detection - RPM
PulseDetResultType = "PulseDetectedRevolution"
PulseDetThresholdType = "Absolute"
PulseDetThresholdValue = 1
PulseDetPulseRevolution = 1
PulseDetHysteresisType = "Absolute"
PulseDetHysteresisValue = 0
PulseDetPulseWidth = 1
PulseDetSlope    = "Rising"
PulseDetInterpolMissValues = 0
'------------ Command -------------------
Set oElementList = ChnPulseDetection("", oChnPulse, "PulseDetectedRevolution", "Absolute", 1, 1, "Absolute", 0, 1, "Rising", 0)
Call LogFileWrite("New result channel '" & oElementList.Item(1).GetReference(eReferenceNameName) & "'")
Set oChnPulseDetectedRevolution = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceNameName))

' Order Analysis for Bode Display
OrderBodeWndFct  = "Hanning"
OrderBodeWndCorrectType = "No"
OrderBodeIntervalType = "NoOfIntervals"
OrderBodeNoOfIntervals = 1
OrderBodeIntervalLength = oChnSensorX.Size
OrderBodeCalcOrder = "1,2,3,4,5"
OrderBodeBandwidthBegin = "0.8,1.8,2.8,3.8,4.8"
OrderBodeBandwidthEnd = "1.2,2.2,3.2,4.2,5.2"
OrderBodeRunoutCompAmplitudeRef = 0
OrderBodeRunoutCompPhaseRef = 0
'------------ Command -------------------
Set oElementList = ChnOrderBodeCalc("", oChnSensorX, oChnPulseStartTime, "Hanning", "No", "NoOfIntervals", 1, 20000, "1,2,3,4,5", "0.8,1.8,2.8,3.8,4.8", "1.2,2.2,3.2,4.2,5.2", 0, 0)
Call LogFileWrite("New channels created by ChnOrderBodeCalc():")
For i = 1 To oElementList.Count
  Call LogFileWrite(String(1,vbTab) & "'" & oElementList.Item(i).GetReference(eReferenceNameName) & "'")
Next
'Show the channels in a VIEW sheet channel table
Call View.NewLayout
Set oArea = View.ActiveSheet.ActiveArea
oArea.DisplayObjType = "ChannelTable"   
For i = 1 To oElementList.Count
  Set o2Dtbl = oArea.DisplayObj.Columns.Add(oElementList.Item(i).GetReference(eReferenceNameName))
Next
Call View.Refresh: Call WndShow("VIEW")

Frequency Weighting (A-B-C Filtering)

This calculation applies frequency weighted digital filtering on a noisy signal according to standards established to evaluate the sensitivity of the human ear to varying frequencies and acoustic pressures. DIAdem uses transfer functions, which attenuate or amplify specific signal frequencies according to the frequency weighted curve specified. The weighted curves A, B, C comply with IEC 61672-1:2003 and DIN EN 61672-1:2003-10 norms. The A evaluation corresponds with curves of the same volume level at 20-40 phon, the B evaluation corresponds with the volume level at 50-70 phon, and the C evaluation corresponds with the volume level at 80-90 phon. The acoustic pressure from the filtered signals is also calculated. The sampling frequency must be between 4 kHz and 1 MHz.

Clear the Data Portal. Selectively load the channel 'Noise data/Noise_1' from the DIAdem example file 'Example_data.tdm' located in the folder 'C:\Program Files\National Instruments\DIAdem ####\Examples\Data\'. From the NAVIGATOR panel, choose 'File', 'New' to clear the Data Portal. Then choose 'File', 'Open...' and the 'Open' dialog will appear. Navigate to the folder 'C:\Program Files\National Instruments\DIAdem ####\Examples\Data\'. Change the file filter at the bottom to 'National Instruments TDM Files'. In the list of files, select the file 'Example_data.tdm'. At the bottom right of the dialog, click on the dropdownbox at the 'Load' button and choose 'Open Selectively...'.

Expand the tree by clicking the '+' sign until the 'Noise data/Noise_1' channel can be selected. Select the 'Noise data/Noise_1' channel and then click the 'Load' button.

It is recommended to convert waveform channels to numeric. Waveform channels are compact and efficient data structures, but they cannot contain an X part that is non-linear (frequency), and some DIAdem tools work better with numeric channels than waveform.

Convert the channel 'Noise_1' from waveform to numeric. From the ANALYSIS panel, choose the menu 'Channel Functions', 'Numeric Channels <-> Waveform Channels'. In the dialog 'Numeric Channels <-> Waveform Channels', choose the 'Conversion mode' of 'Waveform channels -> Numeric channels'. Drag and drop the 'Noise_1' channel from the Data Portal to the channel input control labeled 'Channels:'. Make sure the checkbox 'Keep as waveform channels' is unchecked. Select the 'X-part' option of 'Generate numeric channel (relative time reference)'. Click the 'Calculate' button to perform the conversion. Close the dialog.

Convert the implicit channel 'Time' to explicit. Select the 'Time' channel in the Data Portal. Right click, and from the popup menu select the menu option 'Expand'.

In the steps that follow, a copy of the channel 'Noise_1' will be converted to sound pressure level. Calculate the RMS of the channel. From the ANALYSIS panel, choose the menu 'Basic', 'Calculate RMS...'. Drag and drop the 'Noise_1' channel from the Data Portal to the 'Calculate RMS' dialog channel control labeled 'Y-channel:'. Drag and drop the 'Time' channel from the Data Portal to the channel control 'X-channel'. Set the 'one-sided interval width as % of channel length:' to '0.01' (1%). Make sure the checkbox 'Store result in original channel' is unchecked. Click the 'Calculate' to perform the calculation. &nbps; Close the dialog. Rename the new channel created 'RMS' to 'Noise_1_Level'.

Create a copy of the channel 'Time' by selecting the channel in the Data Portal, right click on it, and choose the 'Copy' option from the popup menu. Select the channel group 'Noise_data' in the Data Portal and then right click and choose 'Paste'. Drag the channel 'Time1' and move it to a position just prior to 'Noise_1_Level'.

Perform a reducing classificaiton on the channel 'Noise_1_Level'. From the ANALYSIS panel, choose the menu option 'Statistics', 'Reducing Classification...'. Configure the 'Reducing Classification' dialog as shown below, making sure to make changes to both the 'Settings' and 'X-Channel tabs. Then click the 'Calculate' button, and then close the dialog.

Convert the channel units to decibels (dB). From the ANALYSIS panel, click on the 'Calculation Manager' toolbar. In the 'Calculation Manager' dialog, click the 'New' toolbar. Click the 'Add Calculation' toolbar and assign the name 'Pa to dB' to the 'Name:' input. Click on the 'Script' tab to activate it. Activate the 'Calculation Script' tab, and in the input area, enter the following (excluding the outside single quotes): 'Call Calculate("Ch(""Noise data/Noise_1_Level"") = Ch(""Noise data/Noise_1_Level"") / VU(10,""µPa"")",,,"dB")'. Make sure the 'Quantity-based' checkbox is checked. Click the 'OK' button. In the 'Calculation Manager' dialog, click on the 'Save' toolbar and save the calculation to a file named 'Pa to dB'. Run the calculation by clicking the toolbar 'Run'. The units for the channel 'Noise_1_Level' should change from 'Pa' to 'dB'. Click the 'OK' button to close the 'Calculation Manager' dialog. Channel 'Noise_1_Level' has now been converted to acoustic pressure in units of decibels.

Filter the data with a Savitzky-Golay filter. From the ANALYSIS panel, choose the menu 'Curve Fitting', and then 'Smooth with Savitzky-Golay Filter'. In the dialog, assign the 'Noise_1' channel to the channel control labeled 'Channel:'. Set the 'Smoothing width on one side (no. of points):' to '50'. Set the 'Order of the polynomial:' to '2'. Make sure the checkbox 'Store result in original channel' is checked. Click the 'Calculate' button to apply the filter.

In the steps that follow, three copies of the 'Noise_1' channel will be created, and then frequency weights of A, B, and C will be applied to each channel in order to evaluate the source channel in terms of the sensitivity of the human ear to frequency and acoustic pressure. In the Data Portal, select the channel 'Time', right click on it and choose 'Copy' from the popup menu. Right click again and select 'Paste'. Drag the new channel 'Time2' to the last position in the Data Portal. In the Data Portal, select the channel 'Noise_1', right click on it and choose 'Copy' from the popup menu. Right click again and select 'Paste'. Drag the new channel 'Noise_2' to the last position in the Data Portal. Rename the channel 'Noise_2' to 'Noise_1_C-Weight'.

In the Data Portal, select the channel 'Time', right click on it and choose 'Copy' from the popup menu. Right click again and select 'Paste'. Drag the new channel 'Time3' to the last position in the Data Portal. In the Data Portal, select the channel 'Noise_1', right click on it and choose 'Copy' from the popup menu. Right click again and select 'Paste'. Drag the new channel 'Noise_2' to the last position in the Data Portal. Rename the channel 'Noise_2' to 'Noise_1_B-Weight'.

In the Data Portal, select the channel 'Time', right click on it and choose 'Copy' from the popup menu. Right click again and select 'Paste'. Drag the new channel 'Time4' to the last position in the Data Portal. In the Data Portal, select the channel 'Noise_1', right click on it and choose 'Copy' from the popup menu. Right click again and select 'Paste'. Drag the new channel 'Noise_2' to the last position in the Data Portal. Rename the channel 'Noise_2' to 'Noise_1_A-Weight'.

From the ANALYSIS panel, choose the menu 'Signal Analysis', and then 'Frequency Weighting (A-B-C Filtering)...'. Drag and drop the 'Noise_1_A-Weight' channel from the Data Portal to the 'Frequency Weighting (A-,B-,C-Filtering)' dialog channel input control labeled 'Signal channel:'. Drag and drop the 'Time2' channel from the Data Portal to the 'Frequency Weighting (A-,B-,C-Filtering)' dialog channel input control labeled 'Time channel:'. At the bottom of the dialog, make sure the checkbox 'Store result in original channel' is not checked. In the 'Evaluation' section, choose the option 'A weighting' and then click the 'Calculate' button.

Drag and drop the 'Noise_1_B-Weight' channel from the Data Portal to the 'Frequency Weighting (A-,B-,C-Filtering)' dialog channel input control labeled 'Signal channel:'. Drag and drop the 'Time3' channel from the Data Portal to the 'Frequency Weighting (A-,B-,C-Filtering)' dialog channel input control labeled 'Time channel:'. At the bottom of the dialog, make sure the checkbox 'Store result in original channel' is not checked. In the 'Evaluation' section, choose the option 'B weighting' and then click the 'Calculate' button.

Drag and drop the 'Noise_1_C-Weight' channel from the Data Portal to the 'Frequency Weighting (A-,B-,C-Filtering)' dialog channel input control labeled 'Signal channel:'. Drag and drop the 'Time4' channel from the Data Portal to the 'Frequency Weighting (A-,B-,C-Filtering)' dialog channel input control labeled 'Time channel:'. At the bottom of the dialog, make sure the checkbox 'Store result in original channel' is not checked. In the 'Evaluation' section, choose the option 'C weighting' and then click the 'Calculate' button. Close the dialog.

If you plot the weighted signals in VIEW, you won't see too much of a difference, as shown below. However, after converting them to sound pressures in units of decibels, the differences will be more apparent.

Calculate the RMS of each channel, using a one-sided interval width as 1% of the channel length. From the ANALYSIS panel, choose the menu option 'Basic', 'Calculate RMS'. In the 'Calculate RMS' dialog, drag and drop the channel 'Noise_1_A-Weight' from the Data Portal to the dialog channel control labeled 'Y-channel:'. Drag the channel 'Time2' from the Data Portal to the dialog channel control labeled 'X-channel:'. In the 'Calculation parameters', set the 'One-sided interval width as % of channel length:' to the value '0.01' (1%). Make sure the checkbox 'Store result in original channel' is checked. Click on the 'Calculate' button. Repeat this for the 'Noise_1_B-Weight' and 'Noise_1_C-Weight' channels. Click the 'Close' button to close the dialog when finished.

Perform a reducing classification on the signals. From the ANALYSIS panel, choose the menu 'Statistics', 'Reducing Classification...'. In the 'Reducing Classificaiton' dialog, assign the channel 'Noise_1_A-Weight_Level' to the dialog channel input control labeled 'Y-channels:' Assign the channel 'Time2' to the channel input control labeled 'X-channel'. Click on the 'Settings' tab, and for the 'Reduction mode', choose the 'Mean' option. Click on the 'X-Channel' tab, and set the 'Determination mode' to 'Automatic' and the 'No. of classes' to '10000'. At the bottom of the dialog, make sure the checkbox 'Store result in original channels' is checked. Click the 'Calculate' button.

Repeat this for the 'Noise_1_B-Weight' and 'Noise_1_C-Weight' channels. Click the 'Close' button to close the dialog when finished.

Convert the channel units to decibels (dB). From the ANALYSIS panel, click on the 'Calculation Manager' toolbar. In the 'Calculation Manager' dialog, click the 'Open' toolbar and then select the 'Pa to dB' calculation file. Double click on the 'Pa to dB' calculation in the list, or select it and click the 'Edit Entry' toolbar. In the 'Calculation Manager - Edit Calculation' dialog, click on the 'Calculation Script' tab and then in the input field, edit the channel references, changing 'Noise_1_Level' to 'Noise_1_A-Weight' for both instances. Click the 'Validate' toolbar button at the top right to validate the calculation. Click the 'Run' toolbar button at the top right to perform the calculation (the units for channel 'Noise_1_A-Weight' will change from 'Pa' to 'dB'). Repeat the process for channels 'Noise_1_B-Weight' and 'Noise_1_C-Weight'. Close the dialog when finished by clicking the 'OK' button for both dialogs. Channels have now been converted to acoustic pressure in units of decibels.

Filter the data with a Savitzky-Golay filter. From the ANALYSIS panel, choose the menu 'Curve Fitting', and then 'Smooth with Savitzky-Golay Filter'. In the dialog, assign the 'Noise_1_A-Weight' channel to the channel control labeled 'Channel:'. Set the 'Smoothing width on one side (no. of points):' to '50'. Set the 'Order of the polynomial:' to '2'. Make sure the checkbox 'Store result in original channel' is checked. Click the 'Calculate' button to apply the filter. Repeat the process for the 'Noise_1_B-Weight' and 'Noise_1_B-Weight' channels, and then close the dialog.

If you plot the 'Noise_1_Level' and the 'Noise_1_A-Weight', 'Noise_1_B-Weight', 'Noise_1_C-Weight' channels in the VIEW panel

A step-by-step script to replicate this analysis is shown below.


'-------------------------------------------------------------------------------
' Frequency Weighting (A-B-C Filtering)

'Derived from:
'	DIAdem help example: 'Frequency Weighting (A-, B-, C-Filtering)'
'	A-B-C-Filtering.vbs
'	Exmple_data.tdm

Dim sPathDocuments, sPathData, oChnX, oChnY, oChnLevelX, oChnLevelY, oElementList, sFormula, arrSymbols(1), arrValues(1)
Dim bCalcQuantityBased, oChnWeightA, oChnWeightB, oChnWeightC
bCalcQuantityBased = CalcQuantityBased
sPathDocuments = ProgramDrv & "Examples\Documents\"
sPathData      = ProgramDrv & "Examples\Data\"
Call Data.Root.Clear()
Call DataFileLoadSel(sPathData & "Example_data.tdm", "TDM", "[2]/[1]", "Load|ChnXYRelation") 

'Convert to waveform because ChnClassXRedXY() doesn't work correctly with waveform channels
Set oChnY = Data.GetChannel("[1]/Noise_1")
If ProgramRevision => 2100 Then 
	Set oElementList =  ChnConvertWaveformToNumeric(oChnY, False, "WfXRelative")
Else
	Set oElementList =  WfChnToChn(oChnY, False, "WfXRelative")
End If
Set oChnX = Data.GetChannel(oElementList.Item(1).GetReference(eReferenceIndexName))
Call ChnValExpand(oChnX)

Set oChnLevelX = oChnY.ChannelGroup.Channels.AddChannel(oChnX)
Set oChnLevelY = oChnY.ChannelGroup.Channels.Add(oChnY.Name & "_Level",DataTypeChnFloat64)
'Calculate the sound pressure level...
Call ChnRMS(oChnX, oChnY, oChnLevelY, 0.01)

'Perform a reducing classification..
ClassNo = 10000
Call ChnClassXRedXY(oChnLevelX, oChnLevelX, oChnLevelY, "Automatic", "Mean", True, False, 0)

'Convert to dB
CalcQuantityBased = True
sFormula = "A = A / VU(10, ""µPa"")"
arrSymbols(1) = "A"
Set arrValues(1) = oChnLevelY
Call Calculate(sFormula, arrSymbols, arrValues, "dB")
CalcQuantityBased = bCalcQuantityBased

'Filter the channel
Call ChnSavitzkyGolayFilter(oChnLevelY, oChnLevelY, 2, 50)

'-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
' A-Weight

'Frequency Weighting (A-B-C Filtering) using A-Weight
Set oChnWeightA = oChnLevelY.ChannelGroup.Channels.Add(oChnY.Name & "_A-Weight",DataTypeChnFloat64)
Call ChnWeightFilter(oChnX, oChnY, oChnWeightA, "AWeight")

'Calculate the sound pressure level...
Set oChnLevelX = oChnY.ChannelGroup.Channels.AddChannel(oChnX)
Set oChnLevelY = oChnY.ChannelGroup.Channels.Add(oChnWeightA.Name & "_Level",DataTypeChnFloat64)
Call ChnRMS(oChnX, oChnWeightA, oChnLevelY, 0.01)

'Perform a reducing classification..
ClassNo = 10000
Call ChnClassXRedXY(oChnLevelX, oChnLevelX, oChnLevelY, "Automatic", "Mean", True, False, 0)

'Convert to dB
CalcQuantityBased = True
sFormula = "A = A / VU(10, ""µPa"")"
arrSymbols(1) = "A"
Set arrValues(1) = oChnLevelY
Call Calculate(sFormula, arrSymbols, arrValues, "dB")
CalcQuantityBased = bCalcQuantityBased

'Filter the channel
Call ChnSavitzkyGolayFilter(oChnLevelY, oChnLevelY, 2, 50)

'-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
' B-Weight

'Frequency Weighting (A-B-C Filtering) using B-Weight
Set oChnWeightB = oChnLevelY.ChannelGroup.Channels.Add(oChnY.Name & "_B-Weight",DataTypeChnFloat64)
Call ChnWeightFilter(oChnX, oChnY, oChnWeightB, "BWeight")

'Calculate the sound pressure level...
Set oChnLevelX = oChnY.ChannelGroup.Channels.AddChannel(oChnX)
Set oChnLevelY = oChnY.ChannelGroup.Channels.Add(oChnWeightB.Name & "_Level",DataTypeChnFloat64)
Call ChnRMS(oChnX, oChnWeightB, oChnLevelY, 0.01)

'Perform a reducing classification..
ClassNo = 10000
Call ChnClassXRedXY(oChnLevelX, oChnLevelX, oChnLevelY, "Automatic", "Mean", True, False, 0)

'Convert to dB
CalcQuantityBased = True
sFormula = "A = A / VU(10, ""µPa"")"
arrSymbols(1) = "A"
Set arrValues(1) = oChnLevelY
Call Calculate(sFormula, arrSymbols, arrValues, "dB")
CalcQuantityBased = bCalcQuantityBased

'Filter the channel
Call ChnSavitzkyGolayFilter(oChnLevelY, oChnLevelY, 2, 50)

'-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
' C-Weight

'Frequency Weighting (A-B-C Filtering) using C-Weight
Set oChnWeightC = oChnLevelY.ChannelGroup.Channels.Add(oChnY.Name & "_C-Weight",DataTypeChnFloat64)
Call ChnWeightFilter(oChnX, oChnY, oChnWeightC, "CWeight")

'Calculate the sound pressure level...
Set oChnLevelX = oChnY.ChannelGroup.Channels.AddChannel(oChnX)
Set oChnLevelY = oChnY.ChannelGroup.Channels.Add(oChnWeightC.Name & "_Level",DataTypeChnFloat64)
Call ChnRMS(oChnX, oChnWeightC, oChnLevelY, 0.01)

'Perform a reducing classification..
ClassNo = 10000
Call ChnClassXRedXY(oChnLevelX, oChnLevelX, oChnLevelY, "Automatic", "Mean", True, False, 0)

'Convert to dB
CalcQuantityBased = True
sFormula = "A = A / VU(10, ""µPa"")"
arrSymbols(1) = "A"
Set arrValues(1) = oChnLevelY
Call Calculate(sFormula, arrSymbols, arrValues, "dB")
CalcQuantityBased = bCalcQuantityBased

'Filter the channel
Call ChnSavitzkyGolayFilter(oChnLevelY, oChnLevelY, 2, 50)

'-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

Frequency Weighted Acceleration

Calculates how intensive mechanical vibrations affect the human body. The result values are a frequency-weighted vibration signal or a floating root mean square, also called K-value. The following evaluation filters are supported:

Wk: Vertical whole-body vibration z-axis (ISO 2631-1)
Wd: Horizontal whole-body vibration x-axis or y-axis (ISO 2631-1)
Wf: Low-frequency vertical whole-body vibration z-axis (ISO 2631-1)
Wc: Horizontal whole-body vibration x-axis (ISO 2631-1)
We: Rotating whole-body vibration (ISO 2631-1)
Wj: Vertical head vibration (ISO 2631-1)
Wb: Vertical whole-body vibration z-axis (ISO 2631-4)
Wh: Hand-arm vibration (ISO 5349-1)
W.B.combined: Whole-body vibration on non-specific posture (DIN 45671-1/VDI 2057-1)