DI-770 Oscilloscope provides five virtual instruments in one

DI-770 and WINDAQ/Scope Manual
frequency in the spectrum analyzer sets the start frequency of the sweep. The highest visible frequency in the spectrum
analyzer sets the stop frequency of the sweep. This is limited to the maximum range of the function generator.
The frequency step size is determined by the frequency range of the spectrum analyzer, divided by the number of bins
in the spectrum. When a sweep is active and a setting in the spectrum analyzer is changed, the sweep parameters will
change accordingly.
At each step, the frequency of the generator will be set to a value that falls exactly in one single bin, therefor no calculation
errors occur and no window is required.
The setting Manual requires that all settings are set by the user. The start and stop frequency can be set freely. The frequency
axis of the spectrum analyzer will be set accordingly, so only the range that is sweeped will be visible.
The frequency step size can be determined from the spectrum length. With each step a frequency will be set that generates
no calculation errors. It's also possible to set the step size manually, but that will probably do generate calculation
errors in the FFT.
Hint: For easy creating frequency response characteristics, set the measure mode of the spectrum analyzer to Measure
maximum values and switch off autoranging for the channels
After setting the sweep parameters, the sweep function can be switched on using the on/off button. During the sweep,
the frequency readout in the display will follow the output frequency.
Note: When the sweep function is used to determine frequency response characteristics, be certain to set the signal
shape to Sine.
Generating a previous measured signal from a file
It is possible to generate previously measured signals with the function generator, provided of course that the amplitude
and frequency of the signal are within the specs of the generator.
Measuring and storing a signal
The function generator has two possibilities to generate previous measured signals. It can either use the DDS mode or
it can use a linear mode.
In the DDS mode, a waveform of 1024 points is used to generate the signal. Due to the DDS technique, very accurate
output signal frequencies can be obtained.
In linear mode, a waveform of 64K points is used. The sample clock of the generator can be set to a number of settings,
in order to obtain different output frequencies. The number of settings is limited. When a stored waveform is
used that is smaller than 64K points, the remaining points are filled with a 0 volt value.
A signal that is measured, stored and later generated, has to meet certain points, in order to be usable.
• The signal has to be measured in channel 1 of the scope.
• For DDS mode, the record length of the scope has to be set to 1024 points, for linear mode to any required
length, but 64K is preferred.
• If possible, the sampling frequency of the scope has to be set in such a way that exactly 1 period of the signal is
captured in the 1024 points or 64K points.
After the signal is measured, it can be saved to disk using Save waveform... from the File-menu.
Setting the function generator
At the left hand side of the display in the generator, a number of signal shape buttons are located, one of them is
named File. With this button a signal from a file can be selected and loaded into the generator.
Pressing this button will pop up a file selection dialog in which the proper waveform file can be selected.
After reading the signal, the amplitude and frequency of the signal can be adjusted using the proper controls.
The Function Generator
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