Volume Resis
of four scales and a Graph Line. The
current
1.
2.
3.
4.
5.
6.
An
thickness of 0.15 cm
connects the Graph Line intersection point to a measured current of 6
am
app
Figure 3
Vol
3.4
Derivation of resistivity equations
The ASTM standard states that volume resistivity (
ρ
) shall be calculated as
follows:
(Equation 1)
Where: R is the volume resistance in ohms.
t is the average thickness of the sample.
A is the effective area of the guarded electrode for the particular
electrode arrangement employed.
For the Model 8009, which uses circular electrodes, A is calculated as follows:
(Equation 2)
Where:D
0
, which is the effective diameter of the guarded electrode (see figure
3-4), is 5.40 cm (2.125 in.). Thus,
or
ρ
A
t
----R
=
A
D2
0
4
-------
=
π
A
2.125
(
)
2
4
--------------------
π
3.55square inches
=
=
A
5.40
(
)
2
4
-----------------
π
22.9square centimeters
=
=
16
17
Содержание 8009
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