Amprobe MultiTest 2000 Manual De Usuario página 159

AMPROBE
MULTITEST2000
The measuring method allows the operator to
define the specific resistance up to the depth
1
corresponding approximately to the distance
"a" between the rods. If you increase the
distance "a" you can reach deeper ground
layers and check the ground homogeneity.
After several ρ measurements, at growing
distances "a", you can trace a profile like the
following ones, after which the most suitable
2
rod is chosen:
Curve1: as ρ decreases only in depth, it's
possible to use only a rod in depth.
Curve2: as ρ decreases only until the depth
3
A, it's not useful to increase the depth of the
rod beyond A.
Curve3: even at an increased depth, ρ does
Earth rods distances "a" (m)
not decrease, therefore a ring rod must be
used.
APPROXIMATE EVALUATION OF THE CONTRIBUTION OF INTENTIONAL RODS (64-
12 2.4.1)
The resistance of a rod Rd can be calculated with the following formulas (ρ = medium
resistivity of the ground).
a) Resistance of a vertical rod
Rd = ρ / L
L= length of the element touching the ground