The following table shows some Rs values and their influence on the impedance measurement range:
Series Resistor Rs Lower Z Limit Upper Z Limit
200 Ω 5 mΩ 1125 Ω
450 Ω 10 mΩ 2250 Ω
499 Ω 11 mΩ 2480 Ω
950 Ω 20 mΩ 4500 Ω
The Shunt-Thru with series resistor configuration suffers from the same systematic error as
the normal Shunt-Thru configuration. Please refer to 8.2.3 Shunt-Thru on page 66 for more
details about the cable-braid-error.
Calibration
The Shunt-Thru with series resistor measurement requires at least one Thru calibration.
Thru calibration must be performed with the series resistors included.
For more details on calibrating a Shunt-Thru measurement, please refer to 10.3.4 Calibrating a Shunt-
Thru or Series-Thru measurement on page 100.
8.4.5 Series-Thru
The Series-Thru measurement configuration is especially suitable to measure very high impedance
values. It is basically an S21 transmission measurement in a special configuration. The impedance is
calculated from the measured S21 parameter.
Measurement information
Bode 100 measures S21 gain and calculates impedance Z using the equation:
The Series-Thru configuration offers high sensitivity for high-impedance DUTs. Impedance values in
the MΩ region can be measured. Using an output amplifier further increases the upper impedance
measurement limit.
Shunt-Thru measurement configuration is not suitable for low-impedance DUTs. It is not
recommended to measure impedance values below roughly 1 kΩ.
One advantage of the series-thru connection is that a shielded test-setup can easily be constructed.
Measurement types and applications
OMICRON Lab
69
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