VeEX MTTplus, User Manual

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The GPS Time of Day (ToD) can also be used to precisely set the local date and time in the test set, using the Sync ToD function, which will apply the local time zone
correction before applying it to the test set system real time clock. This time stamp is used for reports and events, but not for time-sensitive testing.
GPS ToD is also used in One-Way-Delay (OWD) measurements and time is applied directly to each test set before the test starts, so they all have accurate time.
The GPS receiver can be turned OFF if not used, to save battery power.
A satellite table, showing satellites in view, satellites being used and signal to noise ratio, is provided for information only, so the correct antenna installation can be
verified. Geographical coordinates are also provide for information only and it could be used in the future to geo-tag some position-sensitive results. The GPS antenna
must have direct view to the sky. At least four satellites with SNR of 34 dBHz or better are recommended for accurate testing.
Warm Up Times
All precision reference sources require a “warm up” time to achieve high accuracy and stability. The warm up term is being used loosely because it is not just about
attaining the right temperature. It also includes disciplining of a local oscillator, negotiating and stabilizing a clock through protocol messages, etc. Each of the tasks
involved takes time to stabilize before it can be used for testing.
Operational Temperature
It is still a major player in the warm-up waiting time and it all depends on the ambient temperature and the initial temperature of the test set. For example, a test set left in
the trunk of a car in a winter night will take longer to reach operational temperature.
GPS Lock
The time to get an stable clock output varies depending on the conditions, antenna type and installation, sky visibility and whether or not the test set has changed
position. Using the test set for the first time on a new site (different geographical position) would increment the time to its first satellite lock. Users can follow the different
stages (Searching, Sync 1PPS, and Lock) by checking the GPS status GUI at \Utilities \Settings \More \High Precision Clock Source \GPS
Precision Timing Protocol
PTP, like IEEE 1588v2, require some time for the two ends (master and slave) to agree on the current time. This protocol “warm-up” time is dependent on the link
conditions (traffic, latency, delay variations, PTP settings, etc.). Tests shall not be started until the protocol has stabilized and the recovered clock has achieved its
maximum accuracy and stability. This is sometimes referred as “Convergence” or “Sync PDV” convergence. Users can use the long tail of the 1588v2 Sync PDV graph as
an indication the PTP has reached synchronous state.
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5.2 Help
Help provides an online help related to the operation of the test set and the measurements performed. The user can access the table of contents, and hyperlinks. Use the
scroll bars to navigate help content.
Help Menu
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MTTplus e_Manual D07-00-096P RevA00 Page 23 of 66