Fluke PM3082 Service Manual page 439

PERFORMANCE TEST
6.3.16 Vertical deflection; common mode rejection ratio at 1 MHz
The common mode rejection ratio (CMRR) is a measure of susceptibility to common mode signals.
This susceptibility is verified in this test.
Test equipment:
Fluke 5500A mode: levsine (Alternative: constant amplitude sine wave generator SG 503)
Power splitter
Test set up:
5500A
Settings/procedure:
1 - Use a power splitter and two cables of equal length to CH1 and CH2.
Apply a 1 MHz sine-wave signal of 1.6 V(pp into 50Q) to inputs CH1 and CH2.
2 - Press the AUTOSET key.
3 - Use 50Q terminations. Use the internal terminations when available.
4 - Set CH1 and CH2 to 0.1 V/div and adjust the generator voltage for a deflection of 8 divisions.
5 - Set CH1 and CH2 to DC input coupling.
6 - Press the CH1+CH2 key to activate the 'added' mode.
7 - Press the INV key of CH2; the result is the display of CH1-CH2.
8 - Press the ON keys of CH1 and CH2; this switches CH1 and CH2 off and only the differential
signal (CH1 CH2) is now visible.
9 - Readjust the VAR function of CH1 or CH2 for minimum amplitude.
Requirements
Verify that the trace-height of the CH1-CH2 differential signal is less than 0.08 divisions.
Repeat the above settings and procedure for CH3 and CH4 (PM3084/94 only).
6.3.17 Vertical deflection; common mode rejection ratio at 50 MHz
(continuation of 6.3.16)
The common mode rejection ratio (CMRR) indicates the susceptibility to common mode signals at
higher frequencies. The susceptibility is verified in this test.
Settings/procedure:
1 - Use a power splitter and two cables of equal length to CH1 and CH2. Apply a sine-wave signal
of 50 MHz with an amplitude of 0.8 V(pp into 50£2) to inputs CH1 and CH2.
2 - Press the AUTOSET key.
3 - Use a 5012 termination. Use the internal termination when available.
4 - Set CH1 and CH2 to 0.1 V/div and adjust the generator voltage for a deflection of 8 divisions.
OSCILLOSCOPE UNDER TEST
6 - 1 3