
Model 8640B
TM 9-4935-601-14-7&P
PERFORMANCE TESTS
4-44. INTERNAL REFERENCE DRIFT RATE (STABILITY) TEST (Cont'd)
DESCRIPTION:
After a two-hour warm-up period, the internal reference is measured with a frequency counter, a digital to analog
converter, and a strip-chart recorder; frequency variations are noted as the specified changes are made. A quartz
oscillator is used as a time standard when measuring drift as a function of time and line voltage change.
Figure 4-30. Internal Reference Drift Rate (Stability) Test Setup
EQUIPMENT:
Frequency Counter................................................................HP 5327C OPT 003
Temperature Controlled Chamber ......................................... Statham Model 325
Variable Voltage Transformer..........................................................GR W5MT3A
Coaxial Short (Type N Male) .............................................................. HP 11512A
Quartz Oscillator .................................................................................... HP 105B
Digital to Analog Converter ..................................................... HP 581A OPT 002
Recorder (for D/A Converter) ................................................................... HP 680
PROCEDURE:
1. Connect equipment as shown in Figure 4-30 after setting Signal Generator's controls as follows:
TIME BASE REF INT/EXT (on rear panel) ..................................................... INT
COUNTER MODE: LOCK ............................................................................... Off
AM ................................................................................................................OFF
FM ................................................................................................................OFF
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