Stanford Research Systems SR785, Руководство по эксплуатации и программированию

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4-68 Source Menu
SR785 Dynamic Signal Analyzer
The sine source is not triggered. The output is always continuous.
Command: STYP (?) {i}
Chirp
Set the source output to Chirp and display the Chirp Setup menu.
The output is an equal amplitude sine wave at each frequency bin of the FFT spectrum.
This source is useful for measuring transfer functions quickly. Use Source Trigger for
stable time records and phase. The Uniform window should be used since individual
frequencies are not present at all times in the time record. The chirp is exactly periodic
with the FFT time record so the Uniform window does not cause ‘leakage’ problems.
This source is only available for the FFT and Correlation Measurement Groups. The
chirp frequency span and burst time record is linked to either DisplayA or DisplayB. If
the other display has a different span, the chirp span will not be appropriate for that
display.
The chirp source is triggered by External triggers. Set the Trigd Source Mode to trigger
once or with every trigger. With the continuous Trigger, the chirp repeats over and over.
Trigger Caution
If the Chirp source is selected, the triggered FFT measurement phase is stable only if the
input signals are derived from the triggered source output. Turn the source off (or set it
to Sine) when making triggered measurements of external signals (not the source).
Command: STYP (?) {i}
Noise
Set the source output to Noise and display the Noise Setup menu.
The output is broadband noise. This source is useful for estimating transfer functions
quickly. White noise provides equal amplitude per
√
Hz. White noise is useful in
electronic applications. Pink noise rolls off at 3 dB/oct providing equal energy per
octave. Pink noise is preferred for octave analysis.
Burst noise is selected whenever the Burst percentage is less than 100%. The burst noise
source is triggered by External triggers. Set the Trigd Source Mode to trigger once or
with every trigger. With Free Run Trigger Mode, the burst repeats over and over.
In FFT group, the noise bandwidth and burst time record is linked to either DisplayA or
DisplayB. If the other display has a different span, the source may not be appropriate for
that display.
Since the signal is random, windows are always required when making FFT
measurements using the noise source.