VT DSO-2A20 Manual Rev. 1.1
Virtins Technology
the VT DSO outputs the probe calibration signal when the signal generator is not running,
disable it first via [Setting]>[DAC Device]>“Probe CAL” to avoid false trigger. The
record length of the oscilloscope should be equal to the frequency sweep duration of the
signal generator. This is to ensure that an oscilloscope frame captures exactly the entire
frequency sweep process from start to end. The oscilloscope should be set to single
trigger mode and inter-frame averaging is not required. Rectangle Window should be
used in the spectrum analyzer. FFT size of the spectrum analyzer should be equal to or
greater than the Record Length of the oscilloscope. Stop the oscilloscope first before
stopping the signal generator.
Theoretically, unit impulse is an option for the stimulus as well. But it has much less
excitation energy than those mentioned above, resulting in poor signal-to-noise ratio in
the measurement. It is thus not recommended.
(2)
Stimulus with an equal amount of energy per octave of bandwidth in the frequency range
of interest together with octave spectrum analysis
Pink noise can be used as the stimulus. No synchronization between the signal generator
and oscilloscope is required. Just start the signal generator first and then start the
oscilloscope. Inter-frame averaging should be used to get better results. You can set the
number of frames to be averaged by right clicking anywhere within the spectrum
analyzer window, selecting [Spectrum Analyzer Processing]> “Inter-Frame Processing”>
“Linear Average” and choosing a number in the “Frames” field. Rectangle Window
should be used in the spectrum analyzer. FFT size of the spectrum analyzer should be
equal to or greater than the Record Length of the oscilloscope. Stop the oscilloscope first
before stopping the signal generator.
A logarithmic frequency swept sine signal can also be used as the stimulus. Trigger level
should be set properly such that the oscilloscope only gets triggered right after the
frequency sweep starts. Start the oscilloscope first and then start the signal generator. If
the VT DSO outputs the probe calibration signal when the signal generator is not running,
disable it first via [Setting]>[DAC Device]>“Probe CAL” to avoid false trigger. The
record length of the oscilloscope should be equal to the frequency sweep duration of the
signal generator. This is to ensure that an oscilloscope frame captures exactly the entire
frequency sweep process from start to end. The oscilloscope should be set to single
trigger mode and inter-frame averaging is not required. Rectangle Window should be
used in the spectrum analyzer. FFT size of the spectrum analyzer should be equal to or
greater than the Record Length of the oscilloscope. Stop the oscilloscope first before
stopping the signal generator.
(3) Stimulus with an equal amount of energy in each frequency band resolved in the
frequency range of interest in spectrum analysis
Multi-tones with each tone frequency corresponding to the center frequency of each
frequency band resolved in the spectrum analyzer and an equal amplitude mixing ratio
can be used. For example, in 1/3 octave analysis, the center frequencies of the resolved
octave bands are 16Hz, 20Hz, 25Hz, …, 20kHz. Thus, a multi-tone signal consisting of
an equal amount of energy from each of these frequencies should be used as the stimulus.
No synchronization between the signal generator and oscilloscope is required. Just start
the signal generator first and then start the oscilloscope. Rectangle Window should be
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