Chapter 4
Synchronization
©
National Instruments Corporation
4-5
NI PXI-6682 User Manual
increased latency and indeterminate performance from the onboard
buffers. Synchronization performance across switches can be in the
tens of microseconds. If a switch must be used, obtain a 1588 boundary
clock or transparent switch to achieve the best performance. These
devices allow traffic to cross Ethernet collision domains without the
inherent loss in performance from a switch.
•
Ensure that the network is running at 100 Mbps by noting the Speed
LED status. Synchronization performance is degraded when running at
10 Mbps.
Note
If it is impossible to use a 100 Mbps network and you must run IEEE 1588
synchronization using a 10 Mbps network, ensure the network interface of the
NI PXI-6682 is explicitly configured for 10 Mbps Full Duplex operation using the
Windows configuration panels.
GPS Synchronization Best Practices
The embedded GPS receiver in the NI PXI-6682 requires signals from
several satellites to be able to compute precise timing and location. The
more satellites available to the receiver, the more precisely it can determine
time and location. Therefore, the location of the antenna should be such that
it will receive signals from the greatest number of satellites possible. As the
number of satellites visible to the antenna decreases, the synchronization
performance may also decrease. The antenna location should be chosen so
that the antenna has a
clear view of the sky
. There is no strict definition for
clear view of the sky
, but a suitable guideline is that the GPS antenna should
have a straight line of sight to the sky in all directions (360
°
) down to an
imaginary line making a 30
°
angle with the ground. Locations far from
trees and tall buildings which could reflect GPS satellite signals are best.
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