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Figure 4-4
Circuit Model When Measuring 3-terminal Device
As shown in Figure 4-4 (A), changes in measurement results occur as parallel impedance is
formed in relation to Z
the 3-terminal device and the test fixture's GND lead impedance Z
measuring a ceramic vibrator with load capacity, the effect of the parallel impedance will
shift the antiresonance points of the measurement wave (Figure 4-5).
Figure 4-5
mpedance Waveform When Guard Measuring a Ceramic Vibrator with Load
Capacity
By subjecting the fixture impedance model of Figure 4-4 to Y-∆ conversion, Z
approximated as follows:
Where, Z
If the parallel impedance of Z
approximated as follows.
Chapter 4
Specifications and Supplemental Performance Characteristics
(A) Circuit model when measuring
3-terminal device
by the impedance Z
x
Z
(theoretical value)
x
Frequency
(
)
+
+
<
<
<
<
<
=
---------------------------------------------
C
D
T
C
D
<
C D
<
T
= 0.02 + jω (6 x 10
r
<
<
≅
C
D
---------- -
<
C D
<
T
Supplemental Performance Characteristics
caused by the internal impedance Z
r
Z
/Z
impedance waveform
x
ab
(measured value)
-9
)
and Z
is sufficiently large compared to Z
a
b
(B) Circuit model for Y-∆
conversion
. For example, when
r
ab
, Z
can be
r
ab
, Z
of
a
b
can be
45
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