Model 8640B
TM 9-4935-601-14-7&P
PERFORMANCE TESTS
4-42. COUNTER EXTERNAL SENSITIVITY TEST (Cont'd)
2. Set COUNTER MODE Source to EXT 0 550. Slowly tune Signal Generator to 0.5 MHz using RANGE and
FREQUENCY TUNE. The counter should indicate the frequency of the signal at RF OUTPUT at all frequencies.
0.5 to 550 MHz (v)
3. Disconnect RF OUTPUT from COUNTER INPUT. Connect the oscillator to COUNTER INPUT and set it for 500 kHz
at 100 mVrms into 50 ohms. Slowly tune oscillator to 20 Hz. The counter should indicate the frequency of the signal
from the test oscillator at all frequencies.
20 Hz to 500 kHz (v)
4. Set COUNTER MODE Source to EXT 0 10 and slowly tune oscillator from 20 Hz to 10 MHz. The counter should
indicate the frequency of the signal from the test oscillator at all frequencies.
20 Hz to 10 MHz (v)
4-43. INTERNAL REFERENCE ACCURACY TEST
SPECIFICATION:
Accuracy: (after calibration at 25°C and 2-hour warm-up)
Better than ±1 ppm for 15° to 35°C.
Better than t3 ppm for 0° to 55°C.
DESCRIPTION:
A frequency counter is used to measure the Signal Generator's counter accuracy. A temperature controlled chamber is
used to set the temperature.
Figure 4-29. Internal Reference Accuracy Test Setup
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