Teledyne LeCroy DXC100A - Manual (Page 7)

Operator’s Manual
922259-00 Rev A 5
Probe Grounding
The DXC100A Probe Pair is supplied with accessories allowing for three probe
ground connection methods.
In most cases, when the common mode portion of the signal consists mainly of
low frequencies (1 MHz and below), the probe ground leads should not be
connected to the ground of the circuit under test. Instead, they should be
connected to each other to minimize the effects of ground loop currents. The
signal corruption caused by not having the probes connected to the ground of
the circuit under test is common to both inputs and rejected by the differential
amplifier.
However, when working in an environment with high RF ambient noise, it is best
to connect the probe ground leads to a good RF ground near the point where
the signal is being measured.
The best way to determine which probe grounding technique should be used is
to try both methods and use the one that provides the least corruption of the
differential signal. Probe tip to BNC adapters are required when adjusting the
compensation and probe CMRR as they provide the best performance of the
three grounding methods.
Short Calibration Procedure
There are two situations where the Short Calibration Procedure is appropriate:

When the probe calibration status is unknown or it has been a long time
since the probe has been calibrated. A small difference between the two
probes can result in a significant CMRR loss, even though the error may
be so small that it’s irrelevant to transient response. This makes it rather
important to occasionally check the CMRR performance of the probes.
This can be done by performing Part 1 and adjusting as needed.

When critical measurements are required. We recommend checking the
DXC100A CMRR by performing at least Part 1 of the short procedure.
When very high slew rate signals (>1V/ns) are encountered,
performance can be enhanced over that of a full calibration procedure
done with commonly available pulse generators. Notice that the Short
Calibration Procedure is the last step in the Full Calibration Procedure.