Teledyne LeCroy AP034 - Manual (Page 36)

AP034 Active Differential Probe
30 922261-00 Rev A
10. Move the high frequency sine wave generator output cable from the oscilloscope channel 2
input to the Common Mode Drive 50 ohm Termination connector of the AP033/AP034
Calibration Fixture.
11. Set the high-frequency sine wave generator RF Output to ON.
12. Set the oscilloscope to display channel 1 only, set the trigger source to channel 1, and set the
channel 1 vertical scale factor as needed to measure the amplitude of the displayed waveform.
Adjust the trigger level as necessary for a stable display. This is the common mode signal. Turn
on Math Channel A. Press MATH SETUP, then REDEFINE A. Set the A Math type to Average, Avg
Type to Continuous, with 1:15 weighting, of channel 1. Turn off the trace 1 display.
NOTE: The amplitude of the Common Mode signal should be relatively small. If the output
waveform appears to be a 1 Volt square wave, check 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.
13. Measure the peak-to-peak output amplitude of the AP034. Record the reading to two-digit
resolution (xx mV) as “Common Mode Signal at 100 MHz” in the Test Record.
14. Calculate the Common Mode Rejection Ratio (CMRR) at 100 MHz by dividing 2,000 mV by the
measured Common Mode Signal recorded in step B-14 (direct reciprocal of the Common Mode
Gain). Record the result to two-digit resolution (xx:1) in the Test Record.
15. Verify that the CMRR at 100 MHz is greater than 18:1 (25 dB).
16. Turn off the high frequency sine wave generator RF output, and disconnect the output cables.
C. Check Low Frequency CMRR
NOTE: Because greater amplitudes are required to measure the higher CMRR specifications at low
frequencies, the Function Generator will be used in place of the high-frequency sine wave
generator for the low frequency CMRR test.
1. Carefully move the AP034 probe head from the Common Mode Drive 50 ohm Termination
connector of the AP033/AP034 Calibration Fixture to the Common Mode Drive No Termination
connector. Make that sure the probe is fully engaged in the fixture.
2. Set the oscilloscope to display channel 2, the channel 2 input coupling to DC1 MΩ, the channel
2 vertical scale to 5 Volt/div, the horizontal scale to 5 ms/div, and the trigger source to channel
2. Set BW limiting on channels 1 and 2 to 25 MHz.
3. Connect the BNC Tee adapter to the output connector of the Function Generator. Connect a
BNC cable from one end of the BNC Tee adapter to channel 2 of the oscilloscope. Connect a