LeCroy AP034 Instruction Manual page 47

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4. Set the sine wave generator frequency to 70 Hz, and the
output amplitude to 20 V
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
11. Set the oscilloscope to display channel 2 only. Change the
horizontal scale factor to 0.5 µs/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
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.
ISSUED: January 2000
, (4 divisions on the oscilloscope).
p-p
, and the frequency to 1 MHz.
p-p
as measured on channel 2.
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