Teledyne LeCroy AP034 - Manual (Page 37)

Operator’s Manual
922261-00 Rev A 31
second BNC cable from the remaining end of the BNC Tee adapter to the Common Mode Drive
No Termination input connector of the AP033/AP034 Calibration Fixture.
CAUTION: Make sure that the Common Mode Drive No Termination connection is used.
Prolonged application of the power levels used in the low frequency common mode test may
damage the termination resistance in either 50 ohm Termination input of the AP033/AP034
calibration fixture.
4. Set the sine wave generator frequency to 70 Hz, and the output amplitude to 20 V
p-p
, (4
divisions on the oscilloscope). If necessary, adjust the trigger level for a stable display.
5. Set the oscilloscope to display channel 1, but leave the trigger source set to channel 2. Set the
vertical scale of channel 1 to 2 mV/div. Create a math waveform on channel A defined as the
Average of channel 1. Set the average factor as necessary to reduce noise. Increase the zoom
to a factor of four (0.5 mV/division). Turn off the waveform display of all channels except the A
Math waveform.
6. Increase the zoom of the A Math waveform as needed to measure the peak-to-peak amplitude.
This is the common mode signal.
7. Record the displayed “Common Mode Signal at 70 Hz” to two-digit resolution (x.xx mV) in the
Test Record.
8. Calculate the Common Mode Rejection Ratio (CMRR) at 70 Hz by dividing 20 000 mV by the
measured Common Mode Signal recorded in step C-7 (direct reciprocal of the Common Mode
Gain). Record the result to two-digit resolution (xx 000:1) in the Test Record.
9. Verify that the “Common Mode Rejection Ratio at 70 Hz” is greater than 10 000:1 (80 dB).
10. Change the output amplitude of the Function Generator to approximately 8.0 V
p-p
, and the
frequency to 1 MHz.
11. Set the oscilloscope to display channel 2 only. Change the horizontal scale factor to 0.5

s/div,
and the channel 2 vertical scale to 2 V/div. Turn the BWL on channels 1 and 2 to 200 MHz.
12. Adjust oscilloscope trigger level as necessary for a stable display. Adjust the Function Generator
amplitude as needed to maintain 8.0 V
p-p
as measured on channel 2.
13. Turn off the oscilloscope channel 2 display, turn on the display of channel 1 and the A Math
waveform (averaged channel 1). Adjust the scale factor of channel 1 and the Zoom of the A
Math waveform as necessary to accurately measure the amplitude of the averaged signal.
14. Record the displayed “Common Mode Signal at 1 MHz” to two-digit resolution in the Test
Record.