Teledyne LeCroy AP033 - Manual (Page 37)

Operator’s Manual
922260-00 Rev A 31
14. Carefully move the AP033 probe head from the Differential Drive 50 Ohm Termination
connector of the AP033/AP034 Calibration Fixture to the Common Mode Drive 50 Ohm
Termination connector. Make sure the probe is fully engaged in the fixture.
15. Set the oscilloscope to display channel 2, channel 2 vertical scale to 0.5 Volt/div, channel 2
input coupling to DC50Ω, and trigger source to channel 2. If necessary, adjust the trigger
level for a stable display.
16. Set the sine wave generator output amplitude to exactly 2 V
p-p
. (4 divisions on the
oscilloscope).
17. Remove the leveled sine wave generator output cable from the oscilloscope and reconnect
it to the Common Mode Drive 50 Ohm Termination input connector of the AP033/AP034
Calibration Fixture.
18. Set the oscilloscope to display Math channel A (Averaged AP033 Output), and trigger
source to channel 1.
19. Increase the channel 1 vertical sensitivity as needed to view the signal.
20. Measure the peak to peak amplitude of the averaged waveform. This is the common mode
signal.
NOTE: The amplitude of the Common Mode signal should be relatively small. If the output
waveform appears to be a 1-Volt square wave, verify that the Common Mode Drive 50
Ohm Termination connector of the AP033/AP034 Calibration Fixture is being used, and
not the Differential Drive 50 Ohm Termination connector.
21. Record the Common Mode signal amplitude to two-digit resolution (xx0 mV) in the Test
Record as ‘Common Mode Signal at 250 MHz’.
22. Calculate the Common Mode Gain by dividing the Common Mode signal recorded in step
B-21 (in mV) by 2,000 mV.
23. Record the result to two significant places as ‘Common Mode Gain at 250 MHz’ in the Test
Record. (Keep all of the leading zeros or use scientific notation.)
24. Calculate the Common Mode Rejection Ratio (CMRR) at 200 MHz by dividing the
Differential Mode Gain at 250 MHz as recorded in step B-12 by the Common Mode Gain
recorded in step B-23.
25. Record the result as ‘Common Mode Rejection Ratio at 250 MHz’ in the Test Record.
26. Verify that the CMRR at 250 MHz is greater than 5:1 (14 dB).
27. Disconnect the output and frequency reference cables from the leveled sine wave
generator.