28
Startup and Operation
6.5.3
Holdover Estimated Uncertainty Model 1201B/C Only
“Time Quality” is a 2.0 sigma (
σ
) estimate based on time-base processor measurements. This is
basically saying that there is a 95% confidence factor that the clock will be within the estimate
given (e.g. 22.63 nSec) of the GNSS clock.
HOLDOVER ESTIMATED
UNCERTAINTY?
“Uncertainty” provides estimates of clock accuracy when it is no longer synchronized to the
GNSS. Uncertainty is a statistic based on time-base processor measurements of the local oscillator.
Select one of the time intervals of interest: in minutes (15, 30, 60), in hours (2, 4, 8, 12, 24),
and in days (2, 4, 7, 14, 30). Selecting one of the time periods will provide the uncertainty for
that time period with one exception. It takes about seven times the holdover interval to calculate
the estimated uncertainty for that period of time. Therefore the TBP may produce dashes if the
measurement time period is shorter than seven times that time period. For example, it would take
seven hours to calculate uncertainty for sixty minutes.
To view individual uncertainties for each time period, go to the ”UNCERTAINTY?” screen,
press the ENTER key and then the UP or DOWN key to cycle through each value.
6.5.4
Event/Deviation
There are two possible displays when pressing the ENTER key in the EVENT/DEVIATION menu:
one for event recording and one for 1 PPS deviation.
EVENT / DEVIATION
Events or 1 PPS deviation results may be viewed on the front panel LCD, or downloaded
through the serial port. If configured for event, successive events appear when repeatedly pressing
the UP or DOWN keys. If there are no records, the second line will indicate “NO DATA”. If
configured for 1 PPS deviation, it will indicate the mean and sigma of 16 successive values. For
additional detail, please see Section 10.2.1.
Event Display
Press the TIMING key until reaching EVENT/DEVIATION, then press ENTER. Use the UP or
DOWN keys to scroll through the available event records. Events are displayed as follows:
Ch A EVENT nn
ddd:hh:ss.sssssss
Where:
nn
= event number (01 to 50)
ddd
= day of year of the event (001 to 366)
hh
= hour of the event (0 to 23)
mm
= minute of the event (0 to 59)
ss.sssssss
= second and fractional seconds of the event