Dxc100A Probe Short Calibration Procedure; Important Notes; Part 1; Part 2 - LeCroy DXC100A Manual

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.

DXC100A Probe Short Calibration Procedure

Important Notes:

There are two situations where the DXC100A Probe Short Calibration Procedure is appropriate:
1. When the DXC100A 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 (as follows)
and adjusting as needed.
2. When critical measurements are required, checking the DXC100A CMRR by performing at least Part 1 of the
short procedure is recommended. 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 DXC100A Probe Short Calibration Procedure is the last step in the DXC100A Probe Full
Calibration Procedure.
Once you are accustomed to making these adjustments, they become quick and easy. Part 2 can be attempted
when high slew rates (>1V/ns) are encountered, and/or when high frequency (time constraints less than 20ns
and frequencies greater than 1MHz) CMRR is especially important.
Note: Do not change any of the adjustments associated with the +INPUT. Doing so requires checking the
changed adjustment, and perhaps doing the entire DXC100A Probe Full Calibration Procedure.
Refer to Figure 1.1 for the location of adjustments, and to the schematic diagram in Figure 1.2 for guidance.
Both figures can be found at the end of this manual.

Part 1

1. Set the oscilloscope sweep speed to 10µs/div. Connect both probe tips to the same point in the circuit
where a measurement is to be made, and set the DA1855A GAIN, ATTENUATOR and INPUT COUPLING
controls to the same settings to be used in the measurement. Be sure the signal used does not exceed the
maximum common mode voltage allowed: e.g. 155 volts with 10X and DA1855A ATTENUATOR set to X1.
2. Set the DXC100A to 10X. Adjust C8 (-X10 LF) so as to minimize the total deflection.
3. Set the DXC100A to 100X. Adjust C18 (-X100 LF1) so as to minimize the total deflection.

Part 2

4. Set the oscilloscope sweep speed to 20ns/div. Now, set the DXC100A ATTENUATION to X10. Adjust R2 (-X10
HF1) and R8 (-X10 HF2) so as to minimize the total deflection.
5. Set the DX100A ATTENUATION to 100X. Adjust R18 (-X100 HF1) so as to minimize the total deflection.
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Operator's Manual
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