44
(a) Parastic Effect
H
CUR
H
POT
L
POT
L
CUR
Cd
Connection
Point
DUT
C
h
C
l
Ground
(b) Guard Plant reduces
Parastic Effect
H
CUR
H
POT
L
POT
L
CUR
Guard
Plant
Figure 3.6
4.2 Open/Short Compensation
For those precision impedance measuring instrument, the open and
short compensation need to be used to reduce the parasitic effect of
the test fixture. The parasitic effect of the test fixture can be treated
like the simple passive components in figure 3.7(a). When the
DUT is open, the instrument gets the conductance Yp = Gp + j
ω
Cp
(Figure 3.7(b)). When the DUT is short, the instrument gets the
impedance Zs = Rs + j
ω
Ls (Figure 3.7(c)). After the open and
short compensation, Yp and Zs are for calculating the real Zdut
(Figure 3.7(d)).
