Advertisement
USNO permanently files these values
as:
50717.007569 CBT ID: 3128AOO110(H) /Status summary: Operating
normally Power source:
AC
/Log
status: Empty
Oe-15 29.94
26.5 25.4
39949 12.166 2553 15.4 8.3
0.00
-8.7 0.0 0.8 12.8 1.8 5.8
1 . 7
2 . 6
12.3 -12.3
5.2 4 1 . 3
A
computer program
can
sort
and
display the information
in
whatever format is
needed. One might want several devices listed on one page when looking at
snapshot pictures. On the other hand, one might want several consecutive readings
for
a
particular device listed on one page
to
look for trends. Outputting the values
to
a
plotting program is better for trend observation. Although the snapshot
pictures will tell if
a
device is operating normally, it is the plot of
the parameters'
history that will help most in detecting the onset of problems and in fixing the
device when
a
failure occurs.
CLOCK PERFORMANCE
The frequency offset
can
be
set
by either the manufacturer or the
user. Typically,
it is set to Oe-15.
Oscillator control percentage
is a very
important value to monitor. The value can
be positive or negative and like most of the other parameters, the value is very
characteristic of the device, One
standard
may have
an oscillator
control value of
-8.6% and another standard may have a value of
-43.1%. Neither of these
values
done means that the clock is performing (or will perform) poorly. A variation in
the value may suggest a future failure,
and
that will be covered in the next section.
What is important about the oscillator control percentage for performance is its
frequency
and
amount
of
change. This is
an
example of when continuous, periodic
readings are needed. For example, USNO has had at least two
standards that
exhibit a phase or rate change that was coincident with
a
change in its oscillator
control percentage. Such
an
occurrence may be due to the
standard experiencing
an environmental change (temperature andor humidity), a Cesium
Beam
Tube
(CBT) change, or
a
CBT controller board change, or it may
be a
precursor to
a
failure.
The
rf
amps have been found
to
have relatively constant values between 20.0 and
31.0 for each
standard after initial
burn-in. (The values may change somewhat
during the first 1 112 to 2 years of
operation.) The values will differ slightly
from
51
Advertisement
