LI-COR LI7200RS, Инструкция по эксплуатации

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Section 7. Software Reference
The basic principle behind PTP is that the best time keeping can be accomplished
with multiple networked devices by synchronizing all device clocks to the most pre-
cise clock on the network. Each clock on the network has a rating that indicates its
relative accuracy. The IEEE 1588 protocol specifies the use of a Best Master Clock
algorithm to determine which clock on the network is the most accurate. On a net-
work, the most accurate clock becomes the master clock and all other clocks sync
to the master clock.
The software implementation of PTP in the LI-7550 provides accuracy in the 10
microsecond range. Implementation of PTP is most important when the
LI-7550 is used in combination with other network-based sensors such as the
LI-7700 Open Path CH
4
Analyzer. When used with the SmartFlux System, the GPS
clocks will become the master clock for the system.
About Time Keeping
The LI-7500RS and LI-7200RS are network-based instruments and it is possible for
multiple users to log data from a single instrument over multiple TCP/IP con-
nections via the LI-7550 Analyzer Interface Unit. Consequently, the analyzer uses
Coordinated Universal Time (UTC) for its onboard timekeeping tasks. The default
time stamp is therefore UTC based, but local time can be set, if desired.
Generally, we recommend that the system synchronizes its time to the GPS clocks.
The instrument uses a time zone database that includes local time zones that are
kept as constant offset from UTC. These time zones are listed as ‘Etc/GMT’ + offset.
However, these time zone names beginning with ‘Etc/GMT’ have their sign
reversed from what is commonly used. Thus, zones west of GMT have a positive
sign, and those east have a negative sign. For example, US/Central Standard Time is
6 hours behind GMT, and in the database this time zone is listed as ‘Etc/GMT-6’.
Unix time is the number of seconds elapsed since the Unix epoch of 00:00 Coordin-
ated Universal Time (UTC) January 1, 1970 (or 1970-01-01T00:00:0Z ISO 8601).
For example, the time stamp 1262884605 translates to 01/07/2010 at 05:16:45 UTC.
The date and time are converted to a conventional display format (YYYY-MM-DD;
HH:MM:SS) and adjusted based on the time zone setting that you select.
The time stamp in each file header shows the instrument time and time zone.
7-2 LI-7200RS Enclosed CO₂/H₂O Analyzer