Oscilloscope Setup Actions

You can configure the setup of an oscilloscope with the Auto setup or the Default setup option.

To change setup mode, click the arrow next to the button that displays the currently selected setup mode.

  • Auto setup—Enables all channels and automatically configures device settings.
  • Default setup—Returns the device to the default configuration.

    • Settings Changed by Auto Setup

    Setting an oscilloscope to Auto setup changes the following settings to the following values:

    General Settings Value
    Acquisition Mode Normal
    Reference Clock Internal
    Note The Changed by Auto setup value means that Auto setup changes the corresponding setting to different values depending on the signal.
    Vertical Settings Value
    Vertical Coupling Unchanged by Auto setup
    Vertical Bandwidth Full
    Vertical Range Changed by Auto setup
    Vertical Offset 0 V
    Probe Attenuation Unchanged by Auto setup
    Input Impedance Unchanged by Auto setup
    Horizontal Settings Value
    Sample Rate Changed by Auto setup
    Min Record Length Changed by Auto setup
    Enforce Realtime True
    Number of Records 1
    Triggering Settings Value
    Trigger Type Edge if signal present, otherwise Immediate
    Trigger Channel Lowest numbered channel with a signal present
    Trigger Slope Positive
    Trigger Coupling DC
    Reference Position 50%
    Trigger Level 50% of signal on trigger channel
    Trigger Delay 0
    Trigger Holdoff 0
    Trigger Output None

    Set the Sample Rate and the Record Length Manually

    By default, InstrumentStudio optimizes the record length or the sample rate of an oscilloscope when taking measurements.

    Configure the Record Length

    You can configure the record length by setting Data Display to one of the following options:
  • Live—InstrumentStudio sets the maximum record length to 1 million samples.
  • On Demand—InstrumentStudio sets the maximum record length to 10 million samples.

    • Manual Override Mode

    To configure larger records, use Manual Override mode. Manual Override mode allows for the configuration of both the sample rate and the record length of an oscilloscope.

    Note NI recommends that you only enable Manual Override mode for test parameters that require specific sample rate and record length values. Otherwise, to get the best interactive experience with an oscilloscope, do not enable this setting.

    Complete the following steps to enable Manual Override mode:

    1. Click the An icon of three horizontal dots. icon for the instrument to open the Instrument Settings window.
    2. On the Acquisition tab, click the Manual Override mode toggle.
      The toggle is in the On position.
    3. Enter the desired values for Sample Rate and Record Length.
    Note If the sample rate or the record length is configured improperly, enabling Manual Override mode might lead to unexpected graph behavior. For example, if your device does not have enough onboard memory to accommodate measurement settings, your graphs might not render properly. You might also get an error message in InstrumentStudio. Other settings might also cause data to be unreadable or take longer than expected to appear. Take, for example, entering a Sample rate of 1 kS/s with a Record length of 3.5 MS. In this case, it takes around an hour for the measurement data to appear in your oscilloscope panel in InstrumentStudio.

    Acquisition Status

    You can determine the current state of an acquisition by looking at the acquisition status icon. The acquisition status icon is in the Horizontal & Acq. header of an oscilloscope panel.

    InstrumentStudio differentiates between the following acquisition statuses:
  • Triggered—The device met the trigger condition and performed an acquisition according to the specified trigger settings.
  • Auto—After a certain amount of time passes without a trigger firing, the device automatically triggers an acquisition. The Auto status displays briefly when automatic acquisition occurs.
    Note You must set the trigger mode to Auto to enable automatic triggering.
  • Waiting—The device is waiting to take an acquisition until the trigger condition is met.
  • Stopped—The instrument is not running.

    • Interpolation Methods

    You can set the interpolation method of an oscilloscope acquisition from the Instrument Settings window. Click the dropdown menu for the Interpolation method setting in the Acquisition tab of the Instrument Settings window.

    You can set interpolation to one of the following settings:

  • No interpolation—The oscilloscope does not interpolate data.
  • Auto—The oscilloscope interpolates data when the visible time for each division is too small for acquisitions that are performed at the maximum sample rate.
    Note When you set the sample rate of the oscilloscope to Manual, the oscilloscope treats the sample rate that you enter as the maximum sample rate. The Auto interpolation method considers headroom when determining whether to perform interpolation. If the headroom is low between the bandwidth and the sample rate of the oscilloscope, the oscilloscope does not interpolate the data.
  • On—The oscilloscope interpolates data as often as possible and does not take headroom into account. If you set the interpolation method to On, the oscilloscope interpolates data in all cases, except for the following:
    • The Random Interleaved Sampling (RIS) sampling method is set for the oscilloscope.
    • The acquisition uses the peak detect sample mode.
    • The waveform has enough data and does not need interpolation.

    • Sampling Methods

    Depending on the device, you can select different sampling methods from the Instrument Settings window. Click the dropdown menu for the Sampling method setting in the Acquisition tab of the Instrument Settings window. You can set sampling to one of the following methods:

  • Real time—Gathers all the samples for a waveform in one acquisition with one trigger event.
  • RIS—Random Interleaved Sampling (RIS) achieves a higher synthetic sample rate by combining several triggered waveforms.
    • Note Not all oscilloscopes support RIS. See the user manual of your device to determine whether it supports RIS.

    Sample Modes

    You can select different sample modes from the Instrument Settings window. Click the dropdown menu for the Sample mode setting in the Acquisition tab of the Instrument Settings window. You can set sample mode to one of the following settings:
  • Sample—The oscilloscope measures the signal at a fixed time interval (the sample rate).
  • Peak detect—The oscilloscope internally samples the signal at its maximum sample rate. Then the oscilloscope saves the maximum value and the minimum value of the input signal within the configured sample interval. Use Peak detect when you want to acquire measurements for a longer time but you still want to detect transients.
  • Averaging—The oscilloscope averages the waveform data of continuous acquisitions that are based on the averaging count. The oscilloscope performs an exponential moving average and shows the number of averages. The number of averages shows how many waveforms are read and averaged.

    • Add FFT Channels and Markers

    You can use FFT channels with an oscilloscope to measure the amplitude and the frequency of a sample. You can also fetch more detailed measurements and search for peaks with the help of markers.

    Create FFT Channels

    1. From a large oscilloscope panel, click the FFT button in the Add Channels section. A frequency graph appears.
    2. Select a Source for the FFT channel. You can select any single channel that already exists.
    3. Select a Window function for the FFT channel.
    4. (Optional) Configure additional settings for the FFT channel by clicking the An icon of three horizontal dots. icon next to the FFT channel. For more information, see Search for and Compute Peaks.

    Create Markers

    A marker fetches the amplitude (y-location) of a particular sample at the specified frequency (x-location) of a particular sample.

    Note You can only create markers after you create an FFT channel.

    Complete the following steps to create markers:

    1. Select the Markers dropdown menu in the Frequency Graph header.
    2. Select Markers: On to enable markers. The Markers table appears below the frequency graph.
    3. From the Markers table, select the marker that you want to configure. By default, only Marker 0 is enabled.
      Note You can enable markers by selecting a marker from the Markers table. Then, change the marker mode from Off to Normal. You can enable up to 12 markers.
    4. Select the FFT channel that you want to measure with the selected marker.
    5. Enter the frequency where you want to place the marker. The amplitude of the signal at the frequency of the marker is displayed in the Level section of the marker toolbar.
      Note You can view and edit the frequency of all enabled markers in the Markers table. The Markers table also displays the current level, mode, and source channel of the markers.

    Identify and Compute Peaks

    To use the peak search functions to locate peaks, you must first enable at least one FFT channel and one marker. The controls for the peak search functions (An icon of four graphs with different peaks that allow you to search for peaks.) are on the left side of the Frequency tab.

    Peaks are samples for which the amplitude rises and falls around a threshold. You can move a selected marker to the following locations:
    • The highest peak
    • The next highest peak
    • A peak that is directly adjacent to the marker (both left or right)

    Compute Peaks Using Peak Threshold and Peak Excursion

    You can configure peak threshold and peak excursion settings by selecting the A cogwheel icon for the instrument settings menu of InstrumentStudio. icon in the Frequency tab. The A cogwheel icon for the instrument settings menu of InstrumentStudio. icon is directly to the right of the peak search functions (An icon of four graphs with different peaks that allow you to search for peaks.).

    Peak threshold defines the minimum amplitude level that a sample must rise above to be considered a peak. You can set a peak threshold value without setting a peak excursion value. Without peak excursion, InstrumentStudio considers a peak eligible for every amplitude measurement that is above the peak threshold value.

    Peak excursion defines the minimum amplitude variation that is required in a signal to be considered a peak. Peak excursion is always specified in relation to a peak threshold value.

    When you define peak excursion, InstrumentStudio considers a peak eligible if the peak meets all of the following conditions:
    • The signal rises above the threshold level
    • The rise of the signal above the peak threshold matches or exceeds the peak excursion value
    • The fall of the signal from above the peak threshold matches or exceeds the peak excursion value
    • The signal falls below the threshold level
    The following figure and the following table show how to identify eligible peaks:

    A graph that explains how peak threshold and peak excursion values function.

    Table 2. Peak Eligibility Examples
    Peak Peak Eligibility Peak Characteristics
    Peak 1 A green checkmark. Peak 1 meets the excursion condition and is an eligible peak.
    • Rises above the peak threshold
    • The rise above the peak threshold matches or exceeds the peak excursion value
    • The fall from above the peak threshold matches or exceeds the peak excursion value
    • Falls below the threshold level
    Peak 2 A red crossed-out circle. Peak 2 does not meet the excursion condition and is not an eligible peak.
    • Rises above the peak threshold
    • A red crossed-out circle. Does not rise above the peak threshold by at least the peak excursion value
    Peak 3 A red crossed-out circle. Peak 3 does not meet the excursion condition and is not an eligible peak.
    • Rises above the peak threshold
    • The rise above the peak threshold matches or exceeds the peak excursion value
    • A red crossed-out circle. The fall from above the peak threshold does not exceed the peak excursion value
    • A red crossed-out circle. The signal rises above the amplitude level of Peak 3
    Peak 4 A green checkmark. Peak 4 meets the excursion condition and is an eligible peak.
    • Rises above the peak threshold
    • During the rise, Peak 4 slightly falls, which happens after Peak 3
    • However, the rise above the peak threshold matches or exceeds the peak excursion value
    • The fall from above the peak threshold matches or exceeds the peak excursion value
    • Falls below the threshold level
    Peak 5 A red crossed-out circle. Peak 5 is not detected as a peak. A red crossed-out circle. Does not rise above the threshold level
    Peak 6 A green checkmark. Peak 6 meets the excursion condition and is an eligible peak.
    • Rises above the peak threshold
    • The rise above the peak threshold matches or exceeds the peak excursion value
    • During the fall, the signal slightly rises, which appears as Peak 7
    • However, the signal does not rise above the amplitude level of Peak 6 before the signal falls again
    • The total fall, which starts at the amplitude level of Peak 6, exceeds the peak excursion value
    • Falls below the peak threshold
    Peak 7 A red crossed-out circle. Peak 7 does not meet the excursion condition and is not an eligible peak.
    • Falls below the peak threshold
    • The fall from above the peak threshold matches or exceeds the peak excursion value
    • A red crossed-out circle. The rise above the peak threshold does not match or exceed the peak excursion value

    FFT Averaging Modes

    You can perform averaged measurements on an FFT channel to improve measurement accuracy or to help compensate for a low signal-to-noise ratio.

    To configure FFT averaging modes, click the An icon of three horizontal dots. icon for the FFT channel, which opens the Software Channel Settings window.

    You can choose one of the following FFT averaging modes:
  • Disabled—Disables FFT averaging.
  • RMS—Root mean square. RMS averaging averages the energy (or power) of the signal. RMS reduces signal fluctuations, but not the noise floor.
  • Peak hold—Performs a peak hold averaging measurement at each individual frequency line. Peak hold retains the RMS peak levels of the averaged quantities from one FFT record to the next. Peak-hold averaging is the most useful in the following cases:
    • Configuring a measurement system
    • Applying limit testing to a frequency spectrum
    • Applying upper limit testing to a frequency spectrum

    • Measure Power Spectral Density

    Power spectral density measures the power content compared to the frequency of a signal. You can view the power spectral density of a signal when you analyze data in the frequency domain. Power spectral density helps you determine which frequency ranges have strong or weak variations in power.

    1. Add an oscilloscope to the large panel.
    2. Create an FFT channel by selecting the FFT button in the Add Channels section of the large panel.
      A frequency chart opens below the time chart of the large panel.
    3. Configure the FFT Axis settings in the following way:
      1. In the header of the frequency chart, select the Chart Options button.
      2. In the Y-axis section, set Units to V/√(Hz) or dBm/Hz.
      3. In the X-axis section, set Scaling to Logarithmic.
    4. Run the panel if it does not already run.
      InstrumentStudio plots the power spectral density data on the Frequency chart.
    For better frequency resolution, you can configure averaging through the FFT channel settings. You can also modify the resolution bandwidth through the axis settings in Chart Options.