DI-770 Oscilloscope provides five virtual instruments in one
DI-770 Oscilloscope provides five virtual instruments in one
DI-770 Oscilloscope provides five virtual instruments in one
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<strong>DI</strong>-<strong>770</strong> and WINDAQ/Scope Manual<br />
Each third octave is displayed with the same width on the display.<br />
This mode requires that the sampl<strong>in</strong>g frequency is about 44 kHz and the record length is at least<br />
4096 spectral comp<strong>one</strong>nts. When this display mode is switched on, the sampl<strong>in</strong>g frequency and<br />
the record length can no longer be set.<br />
Note: When the spectrum analyzer is set to Hold and the frequency axis is set to octaves or third octaves, the signal<br />
will not match with the axis and the grid until a new measurement is taken.<br />
Sett<strong>in</strong>g the frequency range<br />
The frequency range can be set <strong>in</strong> two ways: us<strong>in</strong>g the menu of by means of special function keys.<br />
The frequency range is determ<strong>in</strong>ed fully on the sample frequency: the frequency range is half of the sample frequency.<br />
To change the Frequency range us<strong>in</strong>g the menu, enter the Frequency axis menu and select the Frequency range item.<br />
A new menu will appear with all possible frequency range sett<strong>in</strong>gs. The Frequency axis menu can also be entered by<br />
press<strong>in</strong>g the right mouse button over <strong>one</strong> of the frequency axis controls or read outs.<br />
The last item <strong>in</strong> the menu is a user def<strong>in</strong>ed sett<strong>in</strong>g. Activat<strong>in</strong>g this item will br<strong>in</strong>g up a dialog box <strong>in</strong> which a self<br />
def<strong>in</strong>ed frequency range (with<strong>in</strong> the <strong>in</strong>strument hardware limitations) can be entered. Due to the way the sample frequency<br />
is generated <strong>in</strong> the hardware, not all frequencies and thus not all frequency ranges can be generated. If an<br />
<strong>in</strong>valid frequency range is entered, the closest valid frequency range will be generated.<br />
The follow<strong>in</strong>g keys can be used to change the frequency range:<br />
<br />
<br />
Set the frequency range <strong>one</strong> step smaller<br />
Set the frequency range <strong>one</strong> step larger<br />
Sett<strong>in</strong>g the spectrum record length<br />
The spectrum analyzer takes a number of samples to determ<strong>in</strong>e the frequency spectrum of the <strong>in</strong>put signal. This number<br />
has to be a power of 2. After the FFT calculation, a spectrum with half of that number spectral comp<strong>one</strong>nts is<br />
obta<strong>in</strong>ed. This number of spectral comp<strong>one</strong>nts is called the Record length.<br />
To change the record length, two ways are available: by means of a menu or by means of function keys.<br />
To change the record length us<strong>in</strong>g the menu, enter the Frequency axis menu and select the Record length item.<br />
Another menu will pop up, conta<strong>in</strong><strong>in</strong>g the available record lengths. The Frequency axis menu can also be entered by<br />
press<strong>in</strong>g the right mouse button over <strong>one</strong> of the frequency axis controls or read outs.<br />
For chang<strong>in</strong>g the record length the follow<strong>in</strong>g function keys are available:<br />
<br />
<br />
Select a shorter record length<br />
Select a longer record length<br />
Note: Calculat<strong>in</strong>g a spectrum is time consum<strong>in</strong>g. The time need for calculat<strong>in</strong>g a spectrum is strongly dependent on<br />
the calculat<strong>in</strong>g power of the computer and of the selected record length.<br />
Sett<strong>in</strong>g up the FFT<br />
FFT w<strong>in</strong>dow function<br />
To reduce 'smear<strong>in</strong>g' errors (See W<strong>in</strong>dow<strong>in</strong>g), a w<strong>in</strong>dow<strong>in</strong>g function can be selected.<br />
The Spectrum Analyzer<br />
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