Stanford Research Systems SR844, User Manual

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SR844 Basics 2-21
SR844 RF Lock-In Amplifier
50
Ω Ω Ω Ω
Sig Z-In 1 M
Ω Ω Ω Ω
Sig Z-In
Wide
Reserve
HIGH NORMAL LOW
NOISE
HIGH NORMAL LOW
NOISE
Sensitivity
1 V C C C C C C
300 mV C C C C C C
100 mV C B B C C B
30 mV C B B C B B
10 mV C B A B B A
3 mV C B A B B A
1 mV C B A B A A
300
µ
V B A A B A A
100
µ
V
B A A B A A
30
µ
V
B A A A A A
10
µ
V
A A A A A A
3
µ
V
A A A A A A
1
µ
V
A A A A A A
300 nV A A A A A A
100 nV A A A A A A
Clearly the Low Noise reserve setting should be used whenever possible. For sensitive
measurements, the Low Noise reserve can provide 60 dB or more of dynamic reserve
while minimizing the coherent pickup.
Another source of coherent pickup is in the experimental setup itself. The signal and
reference cables and grounds are very important, especially at higher reference
frequencies.
The X and Y offsets can be used to cancel the coherent pickup as long as the pickup
remains stable during the experiment.