By usi
this:
or
Wher
Volu
subsequent measured current (I).
tions
or
The ASTM standard states
follo
(Eq
Wher
For the Model 8009, which uses circular electrodes, P is calculated as follows:
P = D
0
π
Where: D
0
, which is the effective diameter of the guarded electrode (see Figure
3-1), is 2.125 inches. Thus,
P = 2.125
π
By substituting the values for g and P into Equation 3, it then looks like this:Sur-
face resistance (R) is derived by dividing the applied test voltage (V) by the sub-
sequent measured current (I). By substituting R with V/I, the following equation
that is used in Section 2 to calculate surface resistivity is realized:
σ
2.125
π
0.125
-----------------R
53.4R
=
=
σ
53.4V
I
---------------ohms
=
Figure 3-4
Electrode dimensions
18
19
Содержание 8009
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