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
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 = 27.0020 26.3150 -3.7436 frequencieskHz = 15.0015 1.0049 7.3500
Version History
Introduced in R2022aR2023a: 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 theCursorMeasurementsConfiguration
object.X location –– These fields are enabled and correspond to the
XLocation
property in theCursorMeasurementsConfiguration
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"
.
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