Operator’s Manual
928334-00 Rev A 3
Introduction
The DXC100A is a high-performance, matched, passive differential probe
pair designed for use with the Teledyne LeCroy DA1855A Differential
Amplifiers. The probe pair consists of two well-matched individual probes
sharing a common compensation box allowing the attenuation factor on
both probes to be simultaneously switched between 10X and 100X. When
used with a Teledyne LeCroy DA1885A Differential Amplifier, the probe’s
attenuation factor is automatically incorporated into the effective gain
display and the decimal properly located in the Precision Voltage Generator
(PVG) display.
Although primarily designed for use with Teledyne LeCroy amplifiers, the
DXC100A can be used with any oscilloscope or plug-in unit with an input
impedance of 1 MΩ/15-26pF and one inch (25.4 mm) spacing between
connectors.
Using Probes with Differential Amplifiers
When using a differential amplifier, it is very important to understand the
role probes play in the overall measurement system performance. Probes
not only make attachment to the circuit under test more convenient, 10X
and 100X attenuating probes also extend the common mode range of the
differential amplifier. For example, the DA1855A amplifier has a common
mode range of ± 15.5 volts when the internal attenuators are set to ÷1 and
155 volts when set to ÷10. The addition of a probe with an attenuation
factor of ten extends the common mode range to 1550 volts or the rating
of the probe, whichever is less.
However there is a trade-off in that the Common Mode Rejection Ration
(CMRR) capability of even highly matched differential probe pairs seldom
matches that of the amplifier. In order to preserve the amplifier’s
performance at the probe tips, it is important to use probes designed for
differential performance. Attempting to use normal 10X or 100X
attenuating oscilloscope probes, even high quality probes, results in very
poor CMRR performance. Nominally matching X1 probes, however, provide
excellent common mode rejection and are recommended.
When making differential measurements, probe compensation is just as
important as it is for single-ended measurements. While probe
compensation is important, how well the probes are matched is essential.
Most probes depend on the accuracy of the oscilloscope’s 1 MΩ input