Anritsu 682XXB - Manual (Page 68)

3-6
INTERNAL TIME BASE
AGING RATE TEST
(Optional) The following test can be used to verify that the 682XXB/683XXB
10 MHz time base is within its aging specification. The instrument de-
rives its frequency accuracy from an internal 100 MHz crystal oscilla-
tor standard. (With Option 16 installed, frequency accuracy is derived
from an internal high-stability 10 MHz crystal oscillator.) An inherent
characteristic of crystal oscillators is the effect of crystal aging within
the first few days to weeks of operation. Typically, the crystal oscilla-
tor’s frequency increases slightly at first, then settles to a relatively
constant value for the rest of its life. The 682XXB/683XXB reference
oscillator aging is specified as <2x10
–8
parts per day (<5x10
–10
with
Option 16).
NOTES
Do not confuse crystal aging with other short term
frequency instabilties; i.e., noise and temperature. The
internal time base of the instrument may not achieve its
specified aging rate before the specified warm-up time of
7 to 30 days has elasped; therefore, this performance test is
optional.
For greatest absolute frequency accuracy, allow the 682XXB/683XXB
to warm up until its RF output frequency has stabilized (usually 7 to
30 days). Once stabilized, the change in reference oscillator frequency
should remain within the aging rate if; (1) the time base oven is not al-
lowed to cool, (2) the instrument orientation with respect to the earth’s
magnetic field is maintained, (3) the instrument does not sustain any
mechanical shock, and (4) ambient temperature is held constant. This
test should be performed upon receipt of the instrument and again af-
ter a period of several days to weeks to fully qualify the aging rate.
Test Setup Connect the 682XXB/683XXB rear panel 10 MHz
REF OUT to the Frequency Reference front panel
input connector labeled 10 MHz when directed to do
so during the test procedure.
3-8 682XXB/683XXB MM
PERFORMANCE INTERNAL TIME BASE
VERIFICATION AGING RATE TEST
1 0 M H z
R E F O U T
6 8 2 X X B / 6 8 3 X X B
F r e q u e n c y R e f e r e n c e
1 0 M H z I n p u t
1 P P S
1 . 5 M H z
1 0 M H z
A B S O L U T E T I M E
M o d e l 3 0 0 F r e q u e n c y R e f e r e n c e
E S C 1 2 3
4 5 6 -
D E L 7 8 9
. 0 E N T E R M O D
Figure 3-1. Equipment Setup for Internal Time Base Aging Rate Test