QUADSCOPE User Guide

Spectrum Analyzer Function

The Spectrum Analyzer function displays the frequency spectrum of the input signal. In other words, it displays the frequency components that make up the signal.

The X-axis shows the frequency while the Y-axis is the amplitude of the frequency components.

The amplitude and frequency* of the fundamental is displayed for each enabled channel.

TIP. The spectrum analyzer function will work best when the vertical scale on the oscilloscope screen is set such that the input signal nearly fills the (oscilloscope) screen vertically. To achieve this, select the oscilloscope function and adjust the vertical scale using the left knob. Then switch back to the spectrum analyzer function (TIP 2: Pressing the right knob and then the window button will switch back to the previous function). Once you have done this, the vertical scale on the spectrum analyzer function can be used to scale the display to your liking.

* To be more precise, this is the center frequency of the FFT bin containing peak amplitude.

Vertical Scale

To adjust the vertical scale (height) of the spectrum, rotate the left knob. The value of the vertical scale - per division - is shown below the grid.

The vertical scale is adjusted separately for each channel. The channel LEDs indicate which channel will be affected when the knob is turned (this is called the selected channel). To change the selected channel, press the CH SEL button.

Vertical Position

To change the vertical position of the channel, press the right knob and simultaneously turn the left knob.

If the layout mode is set to stacked (see below) then the channel can only be positioned within its own vertical area of the screen.

Horizontal Scale

To change the range of frequencies displayed (SPAN), use the right knob. The lowest frequency range is 0Hz-200Hz and the highest frequency range is 0Hz-40kHz.

Horizontal scale adjustment in split-screen (dual timebase) mode

When in split screen (dual timebase) mode, the horizontal scale is adjusted separately for each window. To change the selected window, press the CH SEL button. The window that contains the selected channel will become the selected window and the corresponding window selection LED will light up. Changes to the horizontal scale will then be applied to that window.

When split-screen mode is not active, neither of the window selection LEDs will be lit.

Other spectrum analyzer adjustments

Other spectrum analyzer settings (eg. vertical units, FFT window and measurements) can be adjusted by pressing the ADJUST button. The adjust popup will be displayed. Turn the left knob to select the setting that will be adjusted and the right knob to change the value of that setting. Press the ADJUST button when finished and the adjust popup will close.

Settings that can changed by using the ADJUST button are:

CH VPOS

This will change the vertical position of the channel. The vertical position can also be adjusted by pressing the right knob and simultaneously turning the left knob.

VERT UNITS

Allows the display of the amplitude to be either linear (Volts) or logarithmic (dBm). After changing from Volts to dBm and vice versa you may need to adjust the vertical scale and position.

FFT WINDOW

Allows you to select one of four FFT window functions. These are:

Hamming, Hann, Blackman, Rectangular

This is most useful when the VERT UNITS settting is set to dBm. Just try the different windows to see which works best for your input signal.

MEASUREMENTS

Allows the on-screen measurement (amplitude and frequency of the fundamental) to be hidden or shown.

LAYOUT

Use this to control how the channels are displayed on the screen. The available layout modes are Stacked and Overlaid.

In stacked mode, the channels are 'stacked' vertically and never overlap. Each channel is constrained to their own vertical area of the screen. For example, if two channels are enabled in a window (or when split-screen mode is off), then each will be constrained to half of the height of the screen.

In overlaid mode, the channels overlap each other and each channel can be set to take up the full height of the screen.