Geology Reference
In-Depth Information
(a) Wenner
(b) Two-electrode (pole-pole)
I
ρ
α
= 2π
a
ρ
α
= 2π
a
V
I
∞
I
I
∞
V
V
a
a
a
a
(c) Schlumberger
(d) Gradient
L
2
L
2
-
l
2
I
V
I
Ideal dipole 'a'
where
C
=
Exact
ρ
α
= 2π
ρ
α
= π
C
a
2
l
1 -
X
[
Y
2
+ (1-
X
)
2
]
3/2
1 +
X
[
Y
2
+ (1+
X
)
2
]
3/2
L
2
V
I
Ideal dipole '
a
= 2
l
'
ρ
α
= π
a
I
and
X
=
x
/
L
Y
=
y
/
L
I
a
2
l
V
V
y
x
2
L
L
L
(e) Dipole-dipole
I
ρ
α
= π
n
(
n
+1)(
n
+ 2)
a
V
I
a
n
a
a
(f) Pole-dipole
V
I
ρ
α
= 2
π
n
(
n
+1)
a
∞
I
V
a
n
a
(g) Square array
I
I
V
2π
a
2 -
V
I
V
√
2
ρ
α
=
No factor
a
a
Figure 6.2
Common electrode arrays and their geometric factors. There is
no factor for the diagonal square array, because no voltage difference is
observed over homogeneous ground.
