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This test is used to check the daily aging rate index of the internal time base. Under the
preheating time and environmental conditions meeting the requirements, measure the frequency drift
of the internal time base of the instrument with the standard time base and the frequency comparator
once every 12 h, continuously measure 3 numbers, and take the arithmetic mean as the test result at
the time of t
i
. The measurement is continuously made for more than 7 days, and the average
frequency drift is the internal time base aging rate.
The internal time base aging rate index is tested by the time base manufacturer and is mainly
used to indicate the long-term drift of the frequency standard. There is no specific test in this manual,
but general verification method is given below.
Before the test, the internal time base should be fully preheated. After the instrument is
disconnected from the AC power for 2 h, it needs to be warmed up for 30 days to reach the specified
time base aging rate. If the internal time base and the frequency standard differ greatly in frequency,
“10 MHz Standard Debugging” should be performed to keep the same frequency accuracy of the
internal time base as that of the standard time base.
Due to the impact of the test environment on the accuracy of the internal time base, the test shall
be carried out with the followings ensured:
The ambient temperature changes within ±2
℃
.
The instrument maintains the same direction as the earth‘s magnetic field.
The instrument is at the same height.
The instrument shall not be subjected to any mechanical shock.
b) Test block diagram
10MHz output
10MHz output
Signal generator (tested)
BNC cable
Fig.7.3 Internal Time Base Aging Rate Test
c) Test equipment
Frequency standard
HP5061/CH-47
1 set
Frequency comparator (CH7-45 recommended)
1 set
BNC cable
2 pieces
d) Test procedures
Step 1. Power on and reset it, and warm it up for at least 30 minutes. Step 2. Connect the
device as shown in Fig.7.3.
Step 3. Set the signal generator under test:
Continuous wave 10 GHz, power 0 dBm, and RF
on.
Step 4. The reading of the frequency comparator is relative average frequency offset.
Read a set of relative average frequency offset data every 12 hours, measure three
numbers in each group and take the arithmetic average as the time measurement data
(n=2 measurements per day).
Continuously measure it for 7 days and get a total of 15
measurement data.
Step 5. Calculate the daily aging rate K by the following formula: