Agilent Technologies 4294A Specifications download pdf (Page 121)

C-1

APPENDIX C

Open, short and load compensation

The open/short/load compensation requires the measurement data of a standard DUT with known

values in addition to the open/short measurement data. The residuals of a test fixture, cables or an

additional circuit can be defined as a four-terminal network (a two-terminal pair network)

expressed with A, B, C, D parameters as shown in Figure C-1.

Figure C-1. Open/short/load compensation model

With the assumption that a DUT with impedance of Z

is connected to the front panel terminals, the

instrument would measure an impedance value of Z

. The following relationship defines Z

Given: Z

and Z

+BI

=——————= —————

+DI

The parameters of A, B, C and D can be removed when using the following definitions:

Zo: Measured value when the instrument terminals are open.

Zs: Measured value when the instrument terminals are shorted.

Zsm: Measured value of the standard DUT when connected to the test setup.

Zstd: True (or expected) value of the standard DUT.

Zxm: Measured value of DUT.

Zdut: Corrected value of the DUT.

All of the analysis yields an equation that corrects for impedance error factors:

Zstd (Zo - Zsm) (Zxm - Zs)

Zdut = ————————————————

(Zsm - Zs) (Zo - Zxm)

(Note that each parameter has real and imaginary components.)

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Agilent Technologies 4294A Specifications Page 121