Stanford Research Systems SR844 User Manual page 18

1-8 The Basic Lock-In
19 Reconnect the cable to SIGNAL IN.
20
Press Slope/Oct DOWN until 24 dB is
selected.
21
Press Slope/Oct UP until NO FILTER is
selected.
22 Press Slope/Oct DOWN until 12 dB is
selected.
SR844 RF Lock-In Amplifier
The bargraph rises slowly. In fact, with a filter slope
of 12 dB/oct, it takes about 5 time constants to get
to within 1% of the final reading. In this case, this
takes more than 15 s.
The filter slope is adjusted using the right hand pair
of keys in the Time Constant area. The filter rolloff
can be 6, 12, 18 or 24 dB/oct.
With 24 dB/oct rolloff, it takes about 12 time
constants to get within 1% of the final reading.
Remember, both the time constant and filter slope
affect the output settling time.
No filtering is also available. In this case, the
demodulator outputs are amplified but not filtered.
The high output bandwidth in this case requires that
the outputs be taken from the CH1 or CH2
OUTPUT from the front panel and not from the
displays.
12 dB/oct works well in most situations.