Specifications

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The equation for the test fixture’s additional error is shown below:
eAs/o• 100} (%)
De = Ze/100 (D ≤ 0.1)
Ze : Additional Error for Impedance (%)
De : Additional Error for Dissipation Factor
A : Test Fixture’s Proportional Error (%)
Zs/Zx  100 : Short Offset Error (%)
o• 100 : Open Offset Error (%)
Zs : Test Fixture’s short Repeatability (Ω)
Yo : Test Fixture’s open Repeatability (S)
Zx : Measured Impedance Value of DUT(Ω)
D : Measured D value
Proportional error, open and short repeatability are mentioned in the test fixture’s operational manual and in this acces-
sory guide. By inputting the measurement impedance and frequency (proportional error, open and short repeatability are
usually a function of frequency) into the above equation, the fixture’s additional error can be calculated.
2.1 Proportional Error:
The term, proportional error (A), was derived from the error factor, which causes the absolute impedance error to be
proportional to the impedance being measured. If only the first term is taken out of the above equation and multiplied
bythenA•.hismeansthattheabsolutealueotheimpedanceerrorwillalwaysbeAtimesthemea-
sured impedance. The largeness of proportional error is dependent upon how complicated the test fixture’s construction
is. Conceptually, it is dependent upon the stability of each element of the fixture’s equivalent circuit model. From previ-
ous experience, proportional error is proportional to the frequency squared.
2.2 Short Offset Error:
The term, Zs/Zx 100iscalledshortoseterror.Iismultipliedtothistermthens.Itcanbeconcluded
that this term affects the absolute impedance error, by adding an offset. Short repeatability (Zs) is determined from the
variations in multiple measurements of the test fixture in short condition. After performing short compensation, the
measured values of the short condition will distribute around 0 in the complex impedance plane. The maximum value of
the impedance vector is defined as short repeatability. This is shown in the figure below. The larger short repeatability
is the more difficult it is to measure small impedance values. For example, if the test fixture’s short repeatability is 100
mΩ, then the additional error of an impedance measurement under 100 mΩ will be more than 100%. In essence, short
repeatability is made up of a resistance and an inductance part, which become larger as the frequency becomes higher.
Definition of short repeatability
Appendix Additional Error