Agilent Technologies E4438C - Manual (Page 74)

Performance Tests
Timebase Aging Rate (Manual Test - Option UNJ, Option 506, or Option 1E5 Only)
3-26
4. If the signal drifts a full cycle (360
°
) in less than 2 minutes, refer to “Internal Reference Oscillator
Calibration” on page 4-7 and perform the “Internal Reference Oscillator Adjustment.” After the
adjustment, restart this performance test.
5. Watch the oscilloscope display and monitor the time. Notice the time required for a 360
°
phase change and
record this time as T1.
6. Wait 3 to 24 hours. Record the time that you waited as T2.
7. Repeat steps 1 through 6. Notice the time required for a 360
°
phase change and record this time as T3.
8. Calculate the aging rate as follows:
Aging Rate = (1 cycle/10 MHz) (1/T1
−
1/T3) (24 hours/T2)
Example:
T1 = 351 seconds
T2 = 3 hours
T3 = 349 seconds
= (1 cycle/10 MHz) (1/351s
−
1/349s) (24h/3h)(1.306
×
10 -11 per day)
9. Write the test results on the performance test record located at the end of this chapter. Compare the
results to the limits in the test record.
NOTE If the absolute frequency of the standard and the timebase oscillator are extremely close, you
can reduce the measurement time (T1 and T3) by measuring the time required for a phase
change of less than 360
°
. In step 4, change 1 cycle to 0.5 cycle for 180
°
, or 0.25 cycle for 90
°
.