Stanford Research Systems SR865 Operation Manual page 183

Appendix B
Touch 3 times to decrease the frequency
scale to 39.06 kHz/div.
Move the cursor back to the peak.
4. Touch the {Avgs} tile along the bottom to
display the averaging up/down buttons.
Touch twice to increase the number of
averages to 10.
Touch twice to decrease the number of
averages to 1.
5. Touch the {Live} tile along the bottom to pause
the FFT display.
Touch {Paused} to return to a live display.
Press the [Time Constant Down] key multiple
times to set the time constant to 1 ms.
The FFT Display
always baseband (i.e. the frequency span starts
at 0 Hz or dc).
The cursor readout now reads 100.098 kHz
because each frequency bin has been reduced to
0.6 kHz.
FFT graphs can be averaged to reduce
fluctuations. Averaging is exponential in the
number of averages.
Turn the averaging off to speed up the display.
The FFT may be paused.
When the FFT source is set to the PSD output,
the maximum frequency span is set by the time
constant. The shorter the time constant, the
higher the maximum frequency span. This is
because the PSD output is frequency limited by
SR865 DSP Lock-in Amplifier
165