
Model 8640B
TM 9-4935-601-14-7&P
PERFORMANCE TESTS
4-13. FREQUENCY STABILITY VS TIME AND RESTABILIZATION TIME TEST (Cont'd)
EQUIPMENT:
Frequency Counter ................................................................................... HP 5327C OPT 003
Digital to Analog Converter ..........................................................................HP 581A OPT 002
Recorder (for D/A Converter) ........................................................................................ HP 680
PROCEDURE:
1.
Connect equipment as shown in Figure 4-1 after setting Signal Generator's controls as follows:
COUNTER MODE:
EXPAND ................................................................................... Off
LOCK........................................................................................ Off
Source ..................................................................................... INT
AM............................................................................................................................................................ OFF
FM............................................................................................................................................................ OFF
RANGE .......................................................................................................................................... 32-64 MHz
FREQUENCY TUNE ........................................................................................................................... 50 MHz
RF ON/OFF................................................................................................................................................ON
2.
Set frequency counter to read frequency directly (i.e., not divided down). Use a 1 s gate time so that the last three
digits span from 000 to 999 Hz.
3.
Calibrate the recorder for a zero to full-scale reading that corresponds to a 000 to 999 Hz reading of the frequency
counter's last three digits (i.e., 1 kHz full scale).
4.
Warm up the equipment for two hours. Establish a reference on the recorder and record the generator's output
frequency for 10 minutes. The frequency change in 10 minutes should be <500 Hz (half of full scale).
__________________________ 500 Hz
5.
Set the FREQUENCY TUNE control fully ccw and back again to approximately 50 MHz. After 15 minutes record
the frequency for 10 minutes. The frequency change in 10 minutes should be <500 Hz.
__________________________ 500 Hz
6.
Set RANGE to 16 - 32 MHz and record the frequency for 10 minutes. The frequency change in 10 minutes should
be <250 Hz.
__________________________ 250 Hz
7.
Set RANGE to 32 - 64 MHz and set RF ON/OFF to OFF. After one minute set RF ON/OFF to ON. Wait 10
minutes and record the frequency for 10 minutes. The frequency change for the second 10 minutes should be
<500 Hz.
__________________________ 500 Hz
4-6
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