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

Time Scope Toolstrip

Array Plot Toolstrip

Dynamic Filter Visualizer Toolstrip

Creation

Syntax

cursormeas = CursorMeasurementsConfiguration()

Description

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

Properties

All properties are tunable.

XLocation — x-coordinates of the cursors

[2 8] (default) | two-element vector

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

SnapToData — Position cursors on signal data points

false (default) | true

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

LockSpacing — Lock spacing between cursors

false (default) | true

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

Enabled — Enable cursor measurements

false (default) | true

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

Configure Cursor Measurements Programmatically in Time Scope MATLAB Object

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)

Obtain Measurements Data Programmatically for spectrumAnalyzer object

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

Obtain Measurements Data Programmatically for Spectrum Analyzer Block

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 =

   26.8237
   26.3370
   -5.3604


frequencieskHz =

   15.0015
    1.0049
   12.2739

Version History

Introduced in R2022a

R2023a: Support for Spectrum Analyzer block

The SpectrumAnalyzerBlockConfiguration object now supports the CursorMeasurementsConfiguration object. The CursorMeasurementsConfiguration object enables you to obtain and modify the cursor measurements of the Spectrum Analyzer block programmatically from the command line.

R2022b: Enhancements to Data Cursor Measurements

Starting in R2022b, the CursorMeasurementsConfiguration object has a new LockSpacing property. Use this property to lock the spacing between waveform cursors in the scope window.

In the Measurements tab of the scope UI window, these data cursor settings are new:

• Lock cursor spacing –– This setting corresponds to the LockSpacing property in the CursorMeasurementsConfiguration object.

• X location –– These fields are enabled and correspond to the XLocation property in the CursorMeasurementsConfiguration object.

R2022b: Support for waveform cursors in spectrogram mode

Starting in R2022b, the Spectrum Analyzer supports data cursors even when the scope shows only the spectrogram display.

In the command line, you can edit the CursorMeasurementsConfiguration object when you set the ViewType property of the spectrumAnalyzer object to "spectrogram".