Instructions

AP033 Active Differential Probe
40
C. Adjust Fine DC Balance (R304)
1. Remove the shorting plug from the Logic Board.
2. Change the probe Gain to X10.
3. Reinsert the shorting plug into the two holes near the end of the Logic Board.
(Figure 8.)
4. Re-enter Cal Mode by pushing any one of the four buttons that protrude through
holes in the Logic board.
5. Remove the BNC cable from the precision 50 Ω terminator attached to the
DMM.
6. Short the output BNC connector by reconnecting the cable to the SHORT
connector on the AP033 Calibration Fixture. The SHORT connector is the only
BNC connector on the AP033 Calibration Fixture that does not have
corresponding input pins for the probe tip. It is located on the end of the board
beyond the Common Mode Terminated connector.
7. In Cal Mode, the EFFECTIVE GAIN indicators serve as an adjustment indicator.
The EFFECTIVE GAIN indicators are located on the Logic Board (See Figure 12.) It
may be necessary to hold the boards in your hands to see the indicators while
making the adjustment.
8. Adjust Fine DC Balance (R304) until the ±10 EFFECTIVE GAIN indicator lights.
Figure 12, ÷10 Effective Gain Indicator
9. Disconnect the BNC cable from the short connector. Remove the shorting plug
from the logic board.