Stanford Research Systems SR844, User Manual

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Data Storage 4-23
SR844 RF Lock-In Amplifier
Starting and Stopping a Scan
The
STRT,STRD
,
PAUS
and
REST
commands are used to control data storage.
Basically, the
STRT
command starts data storage after a reset or pause. The
PAUS
command pauses data storage but does not reset the buffer. The
REST
command stops
data storage and resets the buffer data.
Aliasing Effects
In any sampled data stream, it is possible to sample a high frequency signal such that it
will appear to be a much lower frequency. This is called aliasing.
Aliasing occurs whenever the signal being sampled contains components at frequencies
greater than 1/2 the sample rate.
Generally, the highest possible sample rate should be used given the desired storage time.
The lock-in time constant and filter slope should be chosen to attenuate signals at
frequencies higher than 1/2 the sample rate as much as possible.