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R&S
RT-ZZ80
R
S
50 Ω
2V
S
Circuit ground
DUT
Fig. 4-1: Equivalent circuit model of the R&S RT-ZZ80 probe
Table 4-1: Designations
Abbreviation
V
S
V
in
R
S
R
L
R
in
C
in
L
con
In a 50 Ω system, the output resistance of the source, the load resistance of the
DUT and the characteristic impedance of all lines equal exactly 50 Ω. However,
the behavior of the probe in the circuit is determined by the effective source impe-
dance which is the impedance present in the DUT between the probe tip and
ground.
Effective source impedance:
R
R
||
R
25
S
S
L
User Manual 1409.7689.02 ─ 02
V
in
R
L
50 Ω
L
con
Description
Voltage at the test point without probe connected
Voltage at the test point with probe connected,
corresponds to the input voltage of the probe
Source resistance of the DUT
Load resistance of the DUT
Input resistance of the probe
Input capacitance of the probe
Connection inductance,
depends on the type of connection
Measurement Principles
C
in
500 Ω
0.3 pF
Probe ground
R
in
22
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