Main Content

CursorMeasurementsConfiguration

Measure signal values using vertical waveform cursors that track along the signal

Since R2022a

    Description

    Use the CursorMeasurementsConfiguration object to enable waveform cursors. You can control the cursor settings from the toolstrip of the scope or from the command line.

    To display vertical cursors on each signal and to modify the cursor settings in the scope UI, click the Measurements tab and enable Data Cursors. Each cursor tracks a vertical line along the signal. The scope displays the difference between x- and y-values of the signal at the two cursors in the box between the cursors. The cursors appear only when the scope has at least one signal in its display. You can use the mouse to move the vertical cursors left and right.

    Spectrum Analyzer Toolstrip

    Snapshot showing cursor measurements in Spectrum Analyzer toolstrip.

    Time Scope Toolstrip

    Snapshot showing cursor measurements in Time Scope toolstrip.

    Array Plot Toolstrip

    Snapshot showing cursor measurements in Array Plot toolstrip.

    Dynamic Filter Visualizer Toolstrip

    Snapshot showing cursor measurements in Dynamic Filter Visualizer toolstrip.

    Creation

    Description

    cursormeas = CursorMeasurementsConfiguration() creates a cursor measurements configuration object.

    example

    Properties

    expand all

    All properties are tunable.

    x-coordinates of the cursors, specified as a two-element vector of real numbers.

    Scope Window Use

    On the Measurements tab, select Data Cursors and then click Data Cursors to specify the two elements in X location properties.

    Data Types: double

    Position cursors on the signal data points, specified as true or false.

    Scope Window Use

    On the Measurements tab, select Data Cursors and then click Data Cursors to select Snap to data.

    Data Types: logical

    Lock spacing between cursors, specified as true or false. Set this property to true to lock the frequency difference between the cursors.

    Scope Window Use

    On the Measurements tab, select Data Cursors and then click Data Cursors to select Lock cursor spacing.

    Data Types: logical

    Enable cursor measurements, specified as true or false. Set this property to true to enable cursor measurements.

    Scope Window Use

    On the Measurements tab, select Data Cursors.

    Data Types: logical

    Examples

    collapse all

    Create a sine wave and view it in the Time Scope. Enable data cursors programmatically.

    Initialization

    Create the input sine wave using the sin function. Create a timescope MATLAB® object to display the signal. Set the TimeSpan property to 1 second.

    f = 100;
    fs = 1000;
    swv = sin(2.*pi.*f.*(0:1/fs:1-1/fs)).';
    scope = timescope(SampleRate=fs,...
        TimeSpanSource="property",...
        TimeSpan=1);

    Data Cursors

    Enable data cursors in the scope programmatically by setting the Enabled property of the CursorMeasurementsConfiguration object to true.

    scope.CursorMeasurements.Enabled = true;
    scope(swv);
    release(scope)

    Compute and display the power spectrum of a noisy sinusoidal input signal using the spectrumAnalyzer MATLAB® object. Measure the peaks, cursor placements, adjacent channel power ratio, and distortion values in the spectrum by enabling these properties:

    • PeakFinder

    • CursorMeasurements

    • ChannelMeasurements

    • DistortionMeasurements

    Initialization

    The input sine wave has two frequencies: 1000 Hz and 5000 Hz. Create two dsp.SineWave System objects to generate these two frequencies. Create a spectrumAnalyzer object to compute and display the power spectrum.

    Fs = 44100;
    Sineobject1 = dsp.SineWave(SamplesPerFrame=1024,PhaseOffset=10,...
        SampleRate=Fs,Frequency=1000);
    Sineobject2 = dsp.SineWave(SamplesPerFrame=1024,...
        SampleRate=Fs,Frequency=5000);
    SA = spectrumAnalyzer(SampleRate=Fs,SpectrumType="power",...
        PlotAsTwoSidedSpectrum=false,ChannelNames={'Power spectrum of the input'},...
        YLimits=[-120 40],ShowLegend=true);

    Enable Measurements Data

    To obtain the measurements, set the Enabled property to true.

    SA.CursorMeasurements.Enabled = true;
    SA.ChannelMeasurements.Enabled = true;
    SA.PeakFinder.Enabled = true;
    SA.DistortionMeasurements.Enabled = true;

    Use getMeasurementsData

    Stream in the noisy sine wave input signal and estimate the power spectrum of the signal using the spectrumAnalyzer object. Measure the characteristics of the spectrum. Use the getMeasurementsData function to obtain these measurements programmatically. The isNewDataReady function returns true when there is new spectrum data. Store the measured data in the variable data.

    data = [];
    for Iter = 1:1000
        Sinewave1 = Sineobject1();
        Sinewave2 = Sineobject2();
        Input = Sinewave1 + Sinewave2;
        NoisyInput = Input + 0.001*randn(1024,1);
        SA(NoisyInput);
         if SA.isNewDataReady
            data = [data;getMeasurementsData(SA)];
         end
    end

    The panes at the bottom of the scope window display the measurements that you have enabled. The values in these panes match the values in the last time step of the data variable. You can access the individual fields of data to obtain the various measurements programmatically.

    Compare Peak Values

    Use the PeakFinder property to obtain peak values. Verify that the peak values in the last time step of data match the values in the spectrum analyzer plot.

    peakvalues = data.PeakFinder(end).Value 
    peakvalues = 3×1
    
       26.3957
       22.7830
      -57.9977
    
    
    frequencieskHz = data.PeakFinder(end).Frequency/1000
    frequencieskHz = 3×1
    
        4.9957
        0.9905
       20.6719
    
    

    Compute and display the power spectrum of a noisy sinusoidal input signal using the Spectrum Analyzer block. Measure the cursor placements, adjacent channel power ratio, distortion, and peak values in the spectrum by enabling these block configuration properties:

    • CursorMeasurements

    • ChannelMeasurements

    • DistortionMeasurements

    • PeakFinder

    Open and Inspect the Model

    Filter a streaming noisy sinusoidal input signal using a Lowpass Filter block. The input signal consists of two sinusoidal tones: 1 kHz and 15 kHz. The noise is white Gaussian noise with a mean of 0 and a variance of 0.05. The sampling frequency is 44.1 kHz. Open the model and inspect the parameter values in the blocks.

    model = 'spectrumanalyzer_measurements.slx';
    open_system(model)
    

    Access the configuration properties of the Spectrum Analyzer block using the get_param function.

    sablock = 'spectrumanalyzer_measurements/Spectrum Analyzer';
    cfg = get_param(sablock,'ScopeConfiguration');
    

    Enable Measurements Data

    To obtain the measurements, set the Enabled property to true.

    cfg.CursorMeasurements.Enabled = true;
    cfg.ChannelMeasurements.Enabled = true;
    cfg.DistortionMeasurements.Enabled = true;
    cfg.PeakFinder.Enabled = true;
    

    Simulate the Model

    Run the model. The Spectrum Analyzer block compares the original spectrum with the filtered spectrum.

    sim(model)
    

    The panes at the bottom of the spectrum analyzer window display the measurements that you have enabled.

    Use getMeasurementsData function

    Use the getMeasurementsData function to obtain the measurements programmatically.

    data = getMeasurementsData(cfg)
    
    data =
    
      1x5 table
    
        SimulationTime    PeakFinder    CursorMeasurements    ChannelMeasurements    DistortionMeasurements
        ______________    __________    __________________    ___________________    ______________________
    
            9.9962        1x1 struct        1x1 struct            1x1 struct               1x1 struct      
    
    

    The values shown in the measurement panels match the values shown in data. You can access the individual fields of data to obtain the various measurements programmatically.

    Compare Peak Values

    As an example, compare the peak values. Verify that the peak values obtained by data.PeakFinder match with the values in the spectrum analyzer window.

    peakvalues = data.PeakFinder.Value
    frequencieskHz = data.PeakFinder.Frequency/1000
    
    peakvalues =
    
       27.0020
       26.3150
       -3.7436
    
    
    frequencieskHz =
    
       15.0015
        1.0049
        7.3500
    
    

    Version History

    Introduced in R2022a

    expand all