DSO5000 Series Quick Start Guide

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7. Turn the vertical position knob of the selected source channel to adjust the vertical position of the FFT waveform.

8. Turn the vertical VOLTS/DIV knob of the selected source channel to adjust the vertical scale of the FFT waveform.

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Nyquist Frequency and Aliasing in the Frequency Domain

The Nyquist frequency is the highest frequency that any real-time digitizing oscilloscope can acquire without aliasing. This frequency is half of the sample rate. Frequencies above the Nyquist frequency will be under sampled, which causes aliasing. The Nyquist frequency is also called the folding frequency because aliased frequency components fold back from that frequency when viewing the frequency domain.

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Section 4 Using the Horizontal Controls

The horizontal controls consist of: the horizontal scale (SEC/DIV) knob, the horizontal position (POSITION) knob, and the (HORIZ MENU) key.

4.1 To adjust the horizontal scale

4.1.1 Turn the horizontal scale knob to change the horizontal time per division (sec/div) setting.

The sec/div setting changes in a 2- 4- 8 step sequence.

The sec/div setting is also known as the sweep speed.

When the sec/div is set to 80 ms/div or slower, the oscilloscope enters Slow Scan mode.

When the horizontal scale is set to 800 ns or faster, the oscilloscope uses sine(x)/x interpolation to expand the horizontal time base.

The sec/div setting is displayed in the status bar at the top left of the screen. Because all channels are displayed in the same time base (except in the Alternate trigger mode), the oscilloscope displays one sec/div setting for all channels.

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4.1.2 Slow Scan Mode

When the horizontal scale is set to 80 ms/div or slower, the oscilloscope enters Slow Scan mode.

In the Slow Scan mode, peak detect acquisition is used so that no data is missed (even the though the Acquire menu may show a different acquisition mode setting). The oscilloscope acquires sufficient data for the pre- trigger part of the display, then waits for the trigger. When the trigger occurs, the oscilloscope continues to capture data for the post- trigger part of the display.

When using the Slow Scan mode to view low frequency signals, the channel coupling should be set to “DC”.

The Slow Scan mode lets you see dynamic changes (like the adjustment of a potentiometer) on low frequency waveforms. For example, Slow Scan mode is often used in applications like transducer monitoring and power supply testing.

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