Agilent Technologies 16451B, Руководство по эксплуатации

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Figure 3-35. Airgap Eects
T able 3-9. Measurement Error Caused by Airgap
t/d er'=2 er'=5 er'=10 er'=20 er'=50 er'=100
0.001 0.1% 0.4% 1% 2% 5% 9%
0.005 0.5% 2% 4% 9% 20% 33%
0.01 1% 4% 8% 16% 33% 50%
0.05 5% 16% 30% 48% 70% 83%
0.1 8% 27% 45% 63% 82% 90%
Eective Area of Electrode
The guard electrode reduces the error caused by stray capacitance at
the edge of the electrodes as shown in \Guard Electrode ". But the
guard electrode cannot perfectly eliminate the error . This error makes
the apparent area of the guarded electrode larger . T o reduce the error ,
divide the dielectric constant value by the eective area constant.
The eective area constant represents the increase of electrode area
caused by stray capacitance , and is as follows:
when =
a
a
= 1 +
g
d
2 B
a
2
when
a
b
= 1 +
g
d
2 B
b
2
Where ,
B
a
= 1 0
2
2 arctan
g
2t
+
2
2
t
g
2 ln 1 +
g
2t
2
B
b
= 1 0
4
2
t
g
2 ln
h
cosh
g
4t
i
Operation 3-59