Stanford Research Systems SR620, Руководство пользователя

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Specification Guide 27
SR620 Universal Time Interval Counter
FREQUENCY MODE
In frequency mode the measurement resolution and error are given by:
N = number of samples averaged
Resolution
= ±
frequency
gate time
(25 ps)
2
+
(short term stability
×
gate time)
2
+
2
×
( trigger jitter )
2
N
Error
= ±
resolution
±
( timebase error
×
frequency )
±
100 ps
gate time
×
frequency
The SR620's typical single-shot frequency resolution as a function of gate time is shown in Graph 5. The
curves are for the standard oscillator, the optional oven oscillator, and an external high stability reference.
The input signal noise is negligible.
Graph 5: Typical frequency resolution as a function
of gate time for the SR620's three oscillator options.
PERIOD MODE
In period mode the measurement resolution and error are given by:
N = number of samples averaged
Resolution
= ±
period
gate time
(25ps)
2
+ (short term stability × gate time)
2
+ 2 × ( trigger jitter )
2
N
Error = ± resolution ± (timebase error × period ) ±
100ps
gate time
× period