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Synchronization
The NI PXI-6683 Series is capable of achieving tight synchronization with various other
devices using GPS, IRIG-B, PPS, or IEEE 1588. When GPS or IRIG-B are selected as the
synchronization source, the NI PXI-6683 Series module can also serve as an IEEE 1588
grandmaster. The following sections describe the synchronization capabilities of the
NI PXI-6683 Series.
GPS
GPS stands for Global Positioning System, and it is a system of over 2 dozen satellites in
medium Earth orbit that are constantly transmitting signals down to Earth. GPS receivers are
able to detect these signals and determine location, speed, direction and time very precisely. GPS
satellites are fitted with atomic clocks, and the signals they transmit to Earth contain timing
information. This makes the GPS system a precise timing and synchronization source.
The NI PXI-6683 Series has a GPS receiver which powers an active GPS antenna and receives
and processes the RF signals (1.575 GHz) from the satellites. The GPS receiver then generates
a very precise pulse-per-second (PPS) that the NI PXI-6683 Series uses to achieve
sub-microsecond synchronization.
GPS enables the NI PXI-6683 Series to synchronize PXI systems located far away from each
other, as long as GPS satellites are visible to the antenna from each location. Furthermore, once
the NI PXI-6683 Series is synchronized to GPS, it can function as an IEEE 1588 grandmaster to
enable synchronization of external 1588 devices.
IRIG-B
IRIG is a standard used to transmit precise timing information between instruments to achieve
synchronization. IRIG-B is a particular application of the IRIG standard, in which 100 bits of
data are sent every second. Embedded in the data is a seconds’ boundary marker that the
receiving instrument uses to synchronize its timebase to the IRIG source. The rest of the data
contains information such as the time of day, days since the beginning of the year, and
optionally, control functions and the number of seconds since the start of the day, encoded as a
straight binary number.
Refer to Appendix B,
, for more information about the IRIG standard.
The NI PXI-6683 Series can function as an IRIG-B receiver, supporting synchronization to
sources outputting IRIG-B 12X (AM) and IRIG-B 00X (DC), compliant with IRIG 200-04
standard.