A-8
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Appendix A
Specifications
Synchronization Accuracy
Test
*
Synchronization Performance
GPS
†
±40 ns, <8 ns standard deviation
IEEE 1588 3 m Ethernet direct connection
‡
±25 ns, <4 ns standard deviation
IEEE 1588 through a 1588 switch
‡,**
±40 ns, <8 ns standard deviation
IEEE 1588 through a hub
‡,††
±60 ns, <12 ns standard deviation
IEEE 1588 through a switch
‡,‡‡
±25 µs, <150 ns standard deviation
IRIG-B DC
±55 ns, <13 ns standard deviation
IRIG-B AM matching
***,†††
±1.15 µs, <260 ns standard deviation
IRIG-B AM to source
†††
±5 µs, <500 ns standard deviation
PPS
±40 ns, <8 ns standard deviation
*
All synchronization performance figures are based on empirical results and represent typical
behavior. All figures are obtained recording the offset between PPS signals generated by two
NI PXI-6683 Series boards, inside a closed PXI chassis, configured to synchronize to the
particular time reference, at ambient room temperature. Synchronization was performed for
15 minutes before PPS offset recording began. All test durations were at least 12 hours.
†
For the GPS test, two NI PXI-6683 Series boards were independently synchronizing to GPS
and configured to generate a PPS. The specification above represents typical empirical
results. Please note that GPS satellites are only guaranteed to be within 100 ns of UTC.
Therefore, the offset between any two devices synchronizing can be as high as 200 ns plus
the offset of that device to GPS.
‡
Sync interval of 1 second was used for IEEE 1588 tests, and all Ethernet connections were
1 Gbps unless otherwise specified.
**
Hirschmann MAR1040 Gb 1588 switch used.
††
Netgear DS104 Hub used with 100 Mbps links.
‡‡
Airlink 101 Gigabit over copper switch used. For this test, a moderate amount of non-1588
Ethernet traffic was present on the switch.
***
IRIG-B AM matching specification was obtained by setting two NI PXI-6683 Series
boards to synchronize independently to the same IRIG-B AM source and generate a PPS. The
offset between their PPS signals was then measured over a 12 hour period.
†††
IRIG-B performance depends on IRIG-B source stability and quality.