Using the Spectrum Analyzer

1.1

Plug in your <test & measurement device>, then start WaveForms and make sure your device is connected.

If no device is connected to the host computer when WaveForms launches, the Device Manager will launch automatically.

Make sure that the device is plugged in and turned on, at which point it will appear in the Device Manager's device list (1.). Click on the device in the list (“DEMO” devices are also listed, which allow the user to use WaveForms and create projects without a physical device) to select it, then click the Select button (2.) to close the Device Manager.

Note: The Device Manager can be reopened by clicking on the “Connected Device” button in the bottom right corner of the screen (3.), or by selecting “Device Manager” from the “Settings” menu at the top of the screen.

1.2

Once the Welcome page loads, in the Instrument Panel at the left side of the window, click on the Spectrum button to open the Spectrum instrument.

1.3

Once the Spectrum instrument opens, the window contains

2.1 Hardware Setup

In order to measure a signal with the Spectrum 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).

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 Spectrum 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. Change the frequency to 500kHz by selecting the Frequency parameter drop down menu or by typing into the text field.

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

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

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 (labeled 1. in the image to the right) corresponds to the signal captured on analog input channel 1. The blue line (2.) 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 (3.) in the configuration panel at the right side of the window.

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.

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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.

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