Stanford Research Systems SR785, Operating Manual And Programming Reference

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Triggering and the Time Record 1-19
SR785 Dynamic Signal Analyzer
Triggering and the Time Record
This example investigates the trigger and time record. You will need a function generator capable of
providing a 100
µ
s wide pulse at 256 Hz with an amplitude of 1V. The output should have a DC level of
0V.
Make sure you have read ‘The FFT Time Record’ in Chapter 2 before trying this exercise.
1. Press [System]
Display the System menu.
Press <Preset> Preset returns the unit to its default settings.
Press [Enter] to confirm Preset. Preset requires confirmation to prevent accidental
reset. Wait until the self tests are completed.
2. Turn on the generator and choose a pulsed
output waveform. Set the frequency to 256 Hz,
the pulse width to 100
µ
s and the amplitude to
1V. (These settings only need to be
approximate.) Make sure that the DC level of
the output is near 0V.
Connect the generator output to the Ch1 A input
of the analyzer.
The input impedance of the analyzer is 1 M
Ω
. The
generator may require a terminator. Many
generators have either a 50
Ω
or 600
Ω
output
impedance. Use the appropriate feedthrough
termination if necessary. In general, not using a
terminator means that the output amplitude will not
agree with the generator setting.
3. Press [Input]
Select the Input master menu.
Press <Input Config> Select the input configuration submenu
Press <Ch1 Input Range> Choose an input range that doesn’t overload.
Press [1.5]. Select (Vpk) with the knob. Now
press [Enter] Set the input range to about 1.5 Vpk. The channel
1input range indicator at the top of the unit now
should read 1.58 Vpk, the closest allowed input
range to the value you entered. Adjust the pulse
amplitude to that no overloads occur.
4. Press [Active Display]
Let’s change the Measurement for DisplayB. Make
DisplayB the active display.
Press [Display Setup] Select the Display Setup menu.
Press <Measurement> Change the Measurement of the active display (B).