Basic Operation
DSO4000 Series Digital Storage Oscilloscope 22
2.7.2.7 Using Cursors to Measure FFT Spectrum
You may use cursors to take two measurements on the FFT spectrum: amplitude (in dB) and
frequency (in Hz). Amplitude is referenced to 0db that equals 1VRMS here. You may use cursors
to measure at any zoom factor.
Push the CURSOR button, choose the Source option and then select Math. Press the Type option
button to select between Amplitude and Frequency. Click the SELECT CURSOR option to choose
a cursor. Then use the V0 knobs to move Cursor S and Cursor E. Use the horizontal cursor to
measure the amplitude and the vertical cursor to measure the frequency. Now the display at the
DELTA menu is just the measured value, and the values at Cursor S and Cursor E.
Delta is the absolute value of Cursor S minus Cursor E.
2.8 Trigger System
The trigger determines when the oscilloscope begins to acquire data and display a waveform.
Once a trigger is properly set up, the oscilloscope can convert unstable displays or blank screens
to meaningful waveforms.
Here introduce some basic concepts about trigger.
Trigger Source: The trigger can be generated with multiple sources. The most common one is the
input channel (alternative between CH1 and CH2). Whether the input signal is displayed or not, it
can trigger normal operations. Also the trigger source can be any signal connected to an external
trigger channel or the AC power line (only for Edge triggers). The source with the AC power line
shows the frequency relationship between the signal and the AC commercial power.
Trigger Type: The oscilloscope has six types of triggers: Edge, Video, Pulse Width, Slope,
Overtime and Swap.
Edge Trigger uses the analog or digital test circuits for triggering. It happens when the
input trigger source crosses a specified level in a specified direction.
Video Trigger performs a field or line trigger through standard video signals.
Pulse Width Trigger can trigger normal or abnormal pulses that meet trigger conditions.
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