Refer to the following sections for information about setting up an oscilloscope instrument in InstrumentStudio.

Oscilloscope Setup Actions

You can configure the setup of an oscilloscope using two options: Auto setup and Default setup.

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

Settings Changed by Auto Setup

Setting an oscilloscope to Auto setup changes the following settings:

General Settings Value
Acquisition Mode Normal
Reference Clock Internal
Vertical Settings Value
Vertical Coupling Unchanged by Auto Setup.
Vertical Bandwidth Full
Vertical Range Changed by Auto Setup.1 Auto Setup adjusts this setting to different values depending on the signal.[1]
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.[1]
Min Record Length Changed by Auto Setup.[1]
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

Setting Sample Rate and Record Length Manually

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

Configuring 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.

    Do the following steps to enable Manual Override mode:

    1. Click Instrument Settings () in the device instrument panel of the oscilloscope.
    2. Click the Manual Override mode toggle.
      The toggle should be in the On position after clicking.
    3. Enter the desired values for Sample Rate and Record Length.
    Note if the sample rate or the record length are 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, located in the Horizontal & Acq. header of an oscilloscope panel.

    • Triggered—The device met the trigger condition and performed an acquisition based on the specified trigger settings.
    • Auto—After a certain amount of time has passed without a trigger firing, the device automatically triggers an acquisition. The Auto status displays briefly when this occurs.
      Note The trigger mode must be set to Auto to enable automatic triggering.
    • Waiting—The device is waiting to take an acquisition until the trigger condition has been met.
    • Stopped—The instrument is not running.

    Interpolation Method

    You can set the interpolation method of an oscilloscope acquisition to one of the following settings from the Instrument Settings window:
    • No interpolation—The oscilloscope does not interpolate data.
    • Auto—The oscilloscope interpolates data when the visible time per division is too small for acquisitions performed at the maximum sample rate. If you set the sample rate of the oscilloscope to Manual, the oscilloscope treats the sample rate you enter as the maximum sample rate. The Auto interpolation method takes headroom into account when determining whether or not to perform interpolation; if there is low headroom between the oscilloscope's bandwidth and its sample rate, the oscilloscope does not interpolate the data.
    • On—The oscilloscope interpolates data as often as possible without taking headroom into account. If you set the interpolation method to On, the oscilloscope will interpolate data in all cases except for the following:
      • The oscilloscope's sampling method is set to Random Interleaved Sampling (RIS).
      • 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 of an oscilloscope:
    • 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 RIS is not supported on all oscilloscopes. You can select RIS only with supported devices. Refer to your device's documentation to determine whether or not it supports RIS.

    Sample Modes

    You can select one of the following sample modes from the Instrument Settings window when configuring an oscilloscope acquisition with InstrumentStudio:
    • 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 saves the maximum and minimum value of the input signal within the configured sample interval. Use Peak detect when you would like to acquire measurements for a longer time while still being able to detect transients.
    • Averaging—The oscilloscope averages the waveform data of continuous acquisitions based on the averaging count. The oscilloscope performs an exponential moving average and shows the number of averages, which shows how many waveforms have been read and averaged.

    Adding FFT Channels and Markers

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

    Creating FFT Channels

    1. From a large oscilloscope panel, click the FFT button in the Add Channels section. A frequency graph displays.
    2. Select a Source for the FFT channel. You can select any single existing channel.
    3. Select a Window function for the FFT channel.
    4. (Optional) Configure additional settings for the FFT channel by clicking the FFT channel's settings cog. Refer to Searching For and Computing Peaks for more information.

    Creating Markers

    A marker fetches the amplitude (y-location) of a particular sample at a specified frequency (x-location) of a particular sample. Complete the following steps to create a marker or markers:

    1. After creating an FFT channel, select the Markers drop-down in the frequency graph header. Select Markers: On to enable markers and open the marker toolbar.
    2. From the marker toolbar, select a marker to configure. By default, only Marker 0 is enabled.
      Note Enable more markers by selecting a marker from the marker toolbar and changing the marker mode from Off to Normal. You can enable up to 12 markers.
    3. Select the FFT channel the selected marker should measure.
    4. 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 below the frequency graph. The Markers table also displays the markers' current level, mode, and source channel.

    Searching For and Computing Peaks

    After enabling at least one FFT channel and markers, you can use the peak search functions to locate peaks. Peaks are the samples for which the amplitude rises and falls around a threshold. You can move the selected marker to the highest peak, the next highest peak, or an adjacent peak to the left or right of the marker. You can configure the peak threshold and excursion settings by selecting the cog icon next to the peak search functions.

    Computing Peaks Using Peak Threshold and Excursion

    The peak threshold is the minimum amplitude level a sample must rise above to be considered a peak. If peak threshold is enabled but peak excursion is not, every amplitude measurement above the threshold is considered a peak. Set the peak threshold from the peak search settings.

    Peak excursion specifies the minimum amplitude variation required in a signal to be considered as a peak. Peak excursion is always specified with respect to a threshold value. A signal must rise and fall above the threshold level by at least the peak excursion value to be considered as an eligible peak.

    The following figure shows how to identify a valid peak that meets excursion criteria:



    Peak 1 rises and falls by at least the peak excursion value above the threshold. Hence, it follows the excursion criteria.

    Peak 2 is above the threshold level, but it does not rise and fall by the excursion value above the threshold level. Hence, it does not satisfy excursion criteria.

    Peak 3 rises above the threshold value by at least the excursion value, but it does not completely fall by the excursion value. The signal rises and crosses the Peak 3 amplitude level. Hence, it is not an eligible peak.

    Peak 4 rises and falls by at least the peak excursion value above the threshold. Although during the rise it slightly falls (Peak 3) the net rise from the threshold level exceeds the excursion value. Hence, it is considered an eligible peak.

    Peak 5 is below the threshold level. Hence, it is not detected as a peak.

    Peak 6 rises by at least the peak excursion value above the threshold. During the fall, the signal slightly rises (as Peak 7), but it does not rise above peak 6 amplitude level before falling again. The total fall, which starts at the peak 6 amplitude level, is more than the excursion value. Hence, it is an eligible peak.

    Peak 7 falls by the excursion value, but it does not rise by the excursion value. Hence, it does not satisfy excursion criteria.

    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.

    • Disabled—Disables FFT averaging.
    • RMS—Root mean square. RMS averaging averages the energy (or power) of the signal, so it reduces signal fluctuations, but not the noise floor.
    • Peakhold—Performs a peak hold averaging measurement at each individual frequency line and retains the RMS peak levels of the averaged quantities from one FFT record to the next. Peak-hold averaging is the most useful when configuring a measurement system or when applying limit or upper limit testing to a frequency spectrum.

    Measuring Spectral Density

    A power spectral density is the measure of a signal's power content versus frequency. You can view the power spectral density of a signal while analysing data in the frequency domain; this is helpful for determining which frequency ranges have strong or weak variations in power.

    Complete the following steps to measure spectral density in InstrumentStudio:
    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 underneath the large panel time chart.
    3. Configure the FFT Axis settings:
      1. In the header of the frequency chart, select the Chart Options button.
      2. In the Y-axis section, change Units to V/√(Hz) or dBm/Hz.
      3. In the X-axis section, set Scaling to Logarithmic.
    4. Run the panel if it is not already running.
      InstrumentStudio plots power spectral density data on the Frequency chart.
    For better frequency resolution, you can configure averaging through the FFT channel settings, or you can modify the RBW through the axis settings in Chart Options.

    1 Auto Setup adjusts this setting to different values depending on the signal.