Measurement Principles
R&S
®
RT-ZS60
28
User Manual 1418.7342.02 ─ 01
4
Measurement Principles
The R&S
RT-ZS60 active voltage probe provides an electrical connection between
the DUT and the oscilloscope. The probe transfers the voltage of the electrical signal
tapped off the DUT to the oscilloscope, where it is displayed graphically. Although
a probe has a wide variety of specifications, these specifications can be grouped
into two classes of basic requirements:
●
High signal integrity of the transferred signal:
With an ideal probe, the output signal that is transferred to the base unit would
be identical to the input signal between the probe tips, and signal integrity would
be extremely high. Every real probe, however, will transfer the input signal in
altered form. A good probe causes only minimum alterations.
How the probe can fulfill this requirement is mainly determined by its bandwidth.
●
Low loading of the input signal:
Every probe is a load for the signal to be measured. This means that the signal
to be measured changes as soon as the probe is connected. A good probe
should cause only a minimum change to the signal, so that the function of the
DUT is not adversely affected.
How the probe can fulfill this requirement is mainly determined by its input impe-
dance.
The parameters of a probe are usually specified for a minimally short connection
between the probe and the DUT. With longer connections, the connection induc-
tance has a significant effect on the measurement.
The high-frequency behavior of active probes is typically characterized in a 50 Ω
measurement environment. The probe is connected to a 50 Ω line that is fed by a
source with 50 Ω internal impedance and that is terminated into 50 Ω.
The
shows the equivalent circuit model of a probe that is connected to
the DUT.
