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National Instruments Corporation
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NI PXI-6682 User Manual
4
Synchronization
The NI PXI-6682 is capable is 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-6682 can
also serve as an IEEE 1588 grandmaster. The following sections describe
the synchronization capabilities of the NI PXI-6682.
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-6682 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-6682 uses to achieve sub-microsecond synchronization.
GPS enables the NI PXI-6682 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-6682 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
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