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Using the Oscilloscope

This guide walks through the process of setting up WaveForms' Scope instrument and capturing some data. The user interface of the instrument is briefly described.

1. Opening the Scope

1.1

Plug in your <test & measurement device>, then start WaveForms and make sure your device is selected. The “Selected Device” indicator in the bottom right corner of the screen (1.), followed by the serial number of the device.

If the device is not listed, click on the indicator to launch the Device Manager screen. Make sure that the device is plugged in and turned on, at which point it will appear in the Device Manager's list (2.). Click on the device in the list to select it, then click the Select button (3.) to close the device manager.

FIXME image: device manager?


1.2

Once the Welcome page loads, in the instrument panel at the left side of the window, click on the Scope button to open the Scope instrument.

FIXME image: instrument panel callout


1.3

Once the Scope instrument opens, the window contains the data plot (1.) showing captured data, the configuration panel (2.) to right of the plot, and the control toolbar (3.) at the top of the window.

FIXME image: UI callout, numbered


2. Using the Scope

This section walks through setting up the oscilloscope to capture and analyze a simple waveform.

FIXME this guide can be followed using a “Demo” device…

2.1 Hardware Setup

In order to measure a signal with the Scope instrument, there must first be a signal to measure. To this end, step 2.1 of this guide describes setting up a simple loopback circuit that connects the <test & measurement device>'s Waveform Generator and Oscilloscope pins.

Connect the <test & measurement device>'s scope channel 1 pin (orange wire) to the device's wavegen channel 1 output pin (yellow wire). For devices that use differential input channels, such as the Analog Discovery Studio with MTE cables, make sure to connect the scope channel 1 negative pin (orange wire with white stripes) to the ground pin associated with wavegen channel 1 (black wire).

FIXME image: MTE cable loopback???


2.2 Software Setup

With the loopback circuit set up, a signal must now be applied to the analog output pins. WaveForms' Wavegen instrument will be used to accomplish this.

From the Scope instrument, opened in step 1.2, return to WaveForms' Welcome page by clicking on its tab at the top of the screen. In the Welcome tab, open the Wavegen instrument, then click the “Run” button () in the control bar near the top of the window to begin outputting a signal. With default settings, a 1V amplitude (2V peak-to-peak) 1kHz sine wave is applied to the wavegen channel 1 output pin.

For more detail on how to use the Wavegen instrument, please see the Using the Waveform Generator guide.

Return to the Scope instrument by clicking on its tab in the bar at the top of the screen.

FIXME image: arrow to wavegen run button


2.3 Begin Capturing Data

Click the Run button () button in the control bar near the top of the window to begin capturing data on the analog input channels. Captured data will appear in the plot pane as a set of colored lines. The yellow line corresponds to the signal captured on analog input channel 1. The blue line corresponds to the signal captured on analog input channel 2.

Since analog input channel 2 was left “floating” (not connected) while making connections in step 2.1, it can be disabled by clicking the checkbox in the “Channel 2” box (which is surrounded by a blue rectangle) in the configuration panel at the right side of the window.

FIXME image: scope tab, arrow to run button


2.4 Plot Pane Axes

By default, the plot has a vertical range of -2.5V to 2.5V, and a horizontal range of -5ms to 5ms (with respect to the trigger configuration, which will be described later in this guide).

To rescale the horizontal axis of the plot to show only two periods of the sine wave, change the “Time Base” value at the top of the configuration panel at the right side of the window to “200 us/div”. This value can be set by either selecting a new value from the dropdown (the arrow next to the field), or by clicking into the time base field and manually typing it in (including units and an SI prefix). This specific value represents one hundred microseconds per division (vertical line) on the plot.

FIXME image


To rescale the vertical axis of the plot, as before, change the “Range” value in the “Channel 1” box in the configuration panel. A value of “200 mV/div” will fit the sine wave precisely to fill the entire plot pane.


2.5 Quick Measure Cursors

To take a quick measurement of the period and frequency of the sine wave, click the “Quick Measure: Pulse” button () at the top right side of the plot pane. Move the cursor over the sine wave in the plot pane, and observe the values displayed. If the values change too quickly to make out, the capturing of data can be stopped by clicking on the “Stop” button () in the control bar near the top of the window.

FIXME image


2.6 Measurements

To view calculated values for period, frequency, amplitude, and various others, that may not be available through the Quick Measure cursors, click on the “View” menu in the toolbar just above the Run/Stop button. In the dropdown menu, click on “Measurements”. This opens a new Measurements pane to the right of the Plot pane.

FIXME image

When opened, the measurements pane does not contain any values. Click on the “Add” button (), then “Defined Measurement”, to add a new measurement to the list. In the window that pops up, make sure that “Channel 1” is selected in the first list. The second list contains a wide variety of different measurements that can be calculated from data captured from the selected channel. Expand the “Horizontal” selection, then click on “Frequency” and click the “Add” button at the bottom of the popup window. Under “Vertical”, click on “Peak2Peak”, and then “Add” again. Click “Close”.

FIXME image

Each measurement selected in the Add popup will now be displayed in the Measurements pane. As can be seen, the list of measurements now contains estimates of the frequency and peak-to-peak voltage of the captured signal. As expected, these measurements will be listed as approximately 1 KHz and 2V, respectively.

FIXME image


3. Scope User Interface Overview

This section walks through the wide variety of controls and features present in the Scope instrument

3.1 Control Buttons

As seen in Section 2, the “control bar” near the top of the window can be used to stop and start the capturing of data from the analog input pins.

In addition to the Run/Stop button, described above, the Single button can be used to capture a buffer of data based around the first occurrence of a pre-defined trigger. The size of the buffer and when the buffer is captured relative to the trigger event are defined by the Time configuration, described in detail later in this guide.

The control bar also contains the trigger configuration options, described in the next section.


3.2 Triggers

Immediately next to the Single button are a set of options that can be used to configure oscilloscope triggers. When run in continuous mode, the plot pane stays centered on these trigger events. As seen above, when the Single button is pressed, a set of data centered on the next trigger event is captured and plotted.

The Mode dropdown allows the user to select what will happen when the Run button is pressed. For descriptions of the available settings, please see the WaveForms reference manual, available through the Help menu in WaveForms, in the menu bar at the top of the screen. The reference manual is also hosted on the Digilent Wiki at this link: WaveForms Reference Manual.

The Source dropdown allows the user to trigger the oscilloscope based on events in other instruments.

The Condition and Level dropdowns allow the user to describe what type of event to trigger on. For example, the configuration Condition=Rising and Level=1V will generate a trigger event whenever the captured data rises above 1V.

Additional trigger configuration options can be found by clicking on the green down arrow to the right of the level field. Please use the WaveForms Help menu for more information.


3.3 Time Configuration Group

By default, the Time group in the Configuration panel contains the “Position” and “Base” fields. The Position field centers the plot on the selected time, measured from the trigger. This can be used to view data captured before and after the trigger event. The Base field configures the scale used for the horizontal axis of the plot. Using these two settings can be thought of as “panning” and “zooming” the plot.

The gear button () in the Time group can be used to change the units used in the position and division fields.

Additional time and sampling configuration options can be found by clicking the green down arrow at the bottom of the Time group. For instance, the sample count and rate used when capturing data can be manually configured - it should be noted that doing so also automatically changes the position and base settings. More information on these options can be found through the WaveForms Help menu.


3.4 Channel Configuration Groups

Each input channel of the <test & measurement device> can be configured via the associated Channel # group in the Configuration panel. By default, each of these groups contains “Offset” and “Range” fields. The Offset field is used to set the vertical position of the the captured signal in the plot. The Range field is used to set the scale used for the vertical axis of the plot for that channel. The checkbox next to the channel name can be used to enable or disable that channel, as seen in Step 2.3 of this guide.

Additional options for each channel can be found by clicking on that channel's gear button (). These options can be used to: select the units used for the Offset and Range fields, show or hide the signal's noise band in the chart, modify the channel's attenuation, sampling, and coupling, and others. More information on these options can be found through the WaveForms Help Menu.


3.5 Other Channels

Other types of channels can be added to the plot and Configuration pane through the “Add Channel” button.

Math channels can be used to display signals passed through some function. For example, high/low/band pass filters can be applied to signals captured on the analog input channels, and displayed on the plot. Custom functions can be defined using JavaScript syntax.

Reference channels can be used to display custom signals or previously-captured signals, imported from a file, in the plot.

Digital channels can be used to display data captured on the digital input/output channels in a separate pane which appears below the plot. This can be used to view both analog and digital signals at the same time. For more information on how digital data can be viewed and used, refer to the Using the Logic Analyzer guide.


3.6 Additional Configuration Options

The “Options” dropdown above the channel groups contains a set of options that apply to multiple channels at once. For instance, the rate at which the plot is updated can be changed from this menu. For more information on the options available in this menu, please refer to the WaveForms Help menu.


3.7 Chart Pane

The Chart pane displays data captured on the analog input channels. The horizontal axis of the plot represents time before and after the trigger event that initiated the capture. The vertical axis represents the voltage level (or other selected unit, for math and reference channels). Each channel has its own vertical scale, which can be selected by clicking on their identifiers in the top left corner of the plot pane (C1, C2, etc.).

Capture status information can be found next to the channel select buttons, including a state string (Stop / Config / Trig'd). Information about the capture being displayed can be found to the right of the channel select buttons, including the number of samples, sample rate, and a time stamp for when the capture was taken.

Another set of buttons can be found in the upper right corner of the plot pane. The “Thumbnail” button displays a small version of the entire buffer of data, including indicators for what part of the signal the main plot is currently viewing. The three “Quick Measure” tools, “Free”, “Vertical”, and “Pulse” (which were seen in step 2.5 of this guide) can be used to modify how the mouse cursor acts on the plot, presenting several different sets of information depending on the tool used. The “Show entire capture” button zooms the plot all of the way out.

The gear button next to the previous five buttons can be used to change how the plot is displayed, including adding labels, changing the background between light and dark, displaying all channel scales at once, and others. For more information on these options, refer to the WaveForms Help menu.

The “Y” button and dropdown next to the previous gear button can be used to add horizontal cursors to the plot. Vertical cursors can be added to the plot using the “X” button and dropdown in the lower left corner of the plot pane.


3.8 File Menu

The File menu at the top of the window provides the ability to create another Scope instrument, as well as to save and load acquisitions and projects.

Saving an acquisition allows the user to load their captured data back into WaveForms later, for instance, as a signal to be generated by the Wavegen instrument.

Saving a project (with or without any acquisitions) allows the user to close WaveForms without losing their configuration. In addition to this, projects can be shared with others to aid in group projects and guided learning.

Exporting data as an image allows the user to produce a screenshot of the entire Scope tool. Alternatively, captured data can be exported in a variety of different file formats, including CSV, TXT, and TDMS.


3.9 Control Menu

The Control menu at the top of the window provides the same functionality as the Single/Stop/Run buttons, and lists hotkeys that can be used for each.


3.10 View Menu

A wide variety of different view panes can be added to the user interface using the “View” menu in the toolbar above the Single/Run/Stop buttons. Each pane, once opened, can be closed by clicking the “X” button in the top right corner of its pane. A list of each view in the menu is listed below:

  • Add Zoom: Creates an additional plot that can be used to zoom in on particular regions of interest in the signal.
  • Add XY: Creates an additional plot with configurable X and Y axes. For instance, two channels can be plotted against one another to create an IV curve diagram.
  • FFT: Creates plot to display a Fast Fourier Transform diagram of the captured signals.
  • Spectrogram: Creates a spectrogram plot, showing how the frequency components of captured signals change over time.
  • Histogram: Creates a plot that displays percentage of time spent by the signal at each voltage level.
  • Persistence: Creates a plot that places multiple signal captures on the same plot, with color indicating how often a voltage level is detected at a certain time.
  • Data: Creates a chart that exposes raw capture data in a spreadsheet.
  • Measurements: As seen in step 2.6 of this guide, can be used to create a list of characteristics of captured signals.
  • Logging: Allows the user to log captured data directly to a file, over multiple acquisitions. Includes a scripting interface (JavaScript) with examples.
  • Audio: Allows the user to play back captured signals as sound through the host computer's audio output.
  • X/Y Cursors: Lists all cursors that have been added to the plot.
  • Digital: Exposes some functionality of the Logic Analyzer instrument within the Scope instrument, allowing the user to capture and view data from the digital input/output channels. For more information on capturing and viewing digital signals, please see the Using the Logic Analyzer guide.
  • Digital Measurements: Creates a list that can contain features of captured digital signals (frequency, duty cycle, pulse width, etc.).
  • Notes: Creates a text editor pane that can be used to document configuration choices, or whatever other information could be useful to remember.


Next Steps

For technical support, please visit the Scopes and Instruments section of the Digilent Forums. FIXME link

More guides to using the wide variety of features included in WaveForms can be found through the FIXME resource center.

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