3 selecting the series or parallel mode, Electing the, Eries or – B&K Precision 889B - Manual User Manual
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H
CUR
H
POT
L
CUR
L
POT
Zdut
C
o
R
s
L
s
G
o
Z
m
Redundant
Impedance
(Z
s
)
Parastic
Conductance
(Y
o
)
Parastic of the Test Fixture
(a) Parastic Effect of the Test Fixture
H
CUR
H
POT
L
CUR
L
POT
C
o
R
s
L
s
G
o
(b) OPEN Measurement
Y
o
OPEN
Y
o
= G
o
+ j£sC
o
1
(R
s
+ j£s<< )
G
o
+j£sC
o
H
CUR
H
POT
L
CUR
L
POT
C
o
R
s
L
s
G
o
(c) SHORT Measurement
Z
s
SHORT
Z
s
= R
s
+ j£sL
s
Z
m
Y
o
Zdut
Z
m
- Z
s
Zdut =
1-(Z
m
-Z
s
)Y
o
(d) Compensation Equation
Z
s
Figure 4.7
4.3 Selecting the Series or Parallel Mode
According to different measuring requirement, there are series and parallel modes to describe the
measurement results. It is depending on the high or low impedance value to decide what mode to be used.
Capacitor
The impedance and capacitance in the capacitor are negatively proportional. Therefore, the larger
capacitance means the lower impedance, the smaller capacitance means the higher impedance. Figure 4.8
shows the equivalent circuit of capacitor. If the capacitance is small, the Rp is more important than the Rs. If
the capacitance is large, the Rs shouldn’t be avoided. Hence, it is properly to use parallel mode for low
capacitance measurement and series mode for high capacitance measurement.