SRS Labs SR850 - Manual (Page 18)

2-6
13. Press [GAIN/TC]
Press <Synchronous> to select <200 Hz.
Display the Gain and Time Constant menu again.
This turns on synchronous filtering whenever the
detection frequency is below 200 Hz.
Synchronous filtering effectively removes output
components at multiples of the detection frequen-
cy. At low frequencies, this filter is a very effective
way to remove 2f without requiring extremely long
time constants.
The outputs are now very quiet and steady, even
though the time constant is very short. The
response time of the synchronous filter is equal to
the period of the detection frequency (20 ms in this
case).
This concludes this measurement example. You
should have a feeling for the basic operation of the
menus, knob and numeric entry. Basic lock-in
parameters have been introduced and you should
be able to perform simple measurements.
The Basic Lock-in