Stanford Research Systems SR620, Manual

Page: 44 / 124

28 Specification Guide
SR620 Universal Time Interval Counter
PHASE MODE
In phase mode the measurement resolution and error are given by:
N = number of samples averaged
note: the gate time is 10ms in internal mode
Resolution = ± 0 . 001 ° ± 360
( 25 ps )
2
+ ( gate time × short term stability )
2
+ 2 × ( trigger jitter )
2
period
2
× N
1 +
phase × period
360 × gate time





2 




Error
= ±
resolution
±
( timebase error
×
time interval )
±
start trigger level error
±
stop trigger level error
±
0 . 5ns
timebase error × period ± 1 × 10
−
8
× period
×
360°
Graph 6 shows the SR620's single-shot phase resolution as a function of frequency. The resolution may be
increased by averaging.
Graph 6: Single-Shot phase resolution vs.
frequency.
COUNT MODE
The resolution and error for count mode are:
Resolution = ±1 count
Error = ±1 count