Stanford Research Systems SR785, Руководство по эксплуатации и программированию

Страница: 36 / 546

1-20 Triggering and the Time Record
SR785 Dynamic Signal Analyzer
Select (Time1) with the knob and press [Enter]. Choose Time Record of Ch1 for the measurement
in DisplayB (bottom). You should see the pulse on
the bottom display.
5. Press [Trigger]
Select the Trigger menu.
Press <Trigger Source> Change the Trigger Source.
Select (Ch 1) with the knob and press [Enter]. Select internal triggering from the Ch 1 input.
Press <Trigger Level> Adjust the trigger level.
Press [3] [0], select (%) with the knob, and
[Enter]. Set the trigger level as a percentage of full scale.
Adjust the level for a stable time record in
DisplayB.
Press [Auto Scale B] DisplayB (bottom) should display the pulse
waveform at the left edge. In this case, the display
shows the signal pulse as a digital oscilloscope
would.
6. Press [Window]
Select the Window menu.
Because the pulse is much shorter than the time
record, we need to use the Uniform (or Force)
window. The other window functions taper to zero
at the start and end of the time record. Always be
aware of the effect windowing has on the time
record and the FFT.
Press <Window> Select a new window type for both displays
(window type is linked by default).
Select (Uniform) with the knob and press
[Enter]. Notice how the spectrum in DisplayA is changed
by the Uniform window.
Press [Auto Scale A] The spectrum in DisplayA is the sinx/x envelope of
a rectangular pulse. The zeroes in the spectrum
occur at the harmonics of 1/pulse width (1/100
µ
s or
10 kHz.)
7. Press <Window>
Choose a non-optimum window.
Select (Hanning) with the knob and press
[Enter]. Choose the Hanning window. Notice how the
spectrum in DisplayA goes away.
Press [Display Setup] Select the Display Setup menu.