MITS Janus Time Engine
Page 21 of 39
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20200929
3.5.3
Time Frame
The time frame provides a
Time Zone Offset
input. This value is only used when the time
reference is any network time source (PTP or
NTP) or when synchronized to the internal
GPS (optional). Its value is intended to localize
time from UTC.
The offset can be + or – relative to UTC values
(all USA time zone offsets are negative values)
and is set in hours 00 to12 via a drop down list
and may also be adjusted further in 15 minute
increments as shown from a second drop down.
Thus, a selection of – 01 30 subtracts an hour
and 30 minutes from UTC time.
The setting is immediate on the next second
update and is saved to flash within 1 second of
entering a value so that it survives a power cycle.
If the only available time reference transfer standard contains no date or time information (e.g. a
1PPS reference), the time may be set
manually. The
Manual Adjust
requires a
Year
(last two digits), Julian
Day
,
Hour
,
Min
utes and
Sec
onds entry value. In order to
set this to within a second of accuracy the
seconds should be set ahead of real time.
When the real time matches the HH:MM:SS value, click the
Now
button before the next real
time second ticks.
When synchronized to 1PPS the 1 second rollover will be synchronized to the 1PPS tick. If the
MJTE becomes synchronized to an IRIG B signal, the time will be overwritten by that time code.
If the time code is B123 or less (B003), it is necessary to enter a year value manually using this
control. The time (DDD,HH,MM,SS) will be overwritten by the time code. The time code
offset is not used to adjust either the manual or IRIG times.
If the MJTE becomes synchronized to the optional GPS, an NTP or PTP clock, the manual time
setting will be overwritten entirely by the values embedded in those sources including year. The
Time Zone offset, if any, will also be used to report time in any IRIG output.
3.5.4
Leap Second Adjust
A leap second is a one-second adjustment that is occasionally applied to Coordinated Universal
Time (UTC), to accommodate the difference between precise time (as measured by atomic
clocks) and imprecise observed solar time (known as UT1 and which varies due to irregularities
and long-term slowdown in the Earth's rotation). The GPS constellation provides leap seconds
data used by GPS receivers to provide a final corrected time. Similarly leap second values are
provided by NTP and PTP master clocks as part of the synchronization data needed by devices
attempting to slave to and apply accurate time as needed.
