Hioki FT6031 - Cautions and Tips for Measurement; Distance between Earthing Electrodes

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Cautions and Tips for Measurement
2.8 Cautions and Tips for Measurement
Distance between earthing electrodes
When the distance between E-H(C) is I m as shown in Figure (a), if
the resistance of the earthing element E is measured while changing
the distance x m between the electrodes E-S(P), measurement
results such as shown in (b) are obtained.
Therefore, its error becomes greater as the location of the auxiliary
earthing rod S(P) moves closer to the earthing element E or
auxiliary earthing rod H(C).
In addition, if the distance between the electrodes E-H(C) is short,
the measurement error is greater as the earth resistance under test
(Rx) and the earth resistance of auxiliary earthing rod (Rc) cannot
be separated from each other.
If earthing is provided by a building structure etc. in a large area, the
resistance area indicated in (a) becomes very wide.
In order to carry out accurate measurement, the auxiliary earthing
rods (S(P) and H(C)) need to be installed at a location well away
from the earthing element (Rx).
As to conrm the above, carry out measurements at several
locations while moving the location of the auxiliary earthing rod S(P)
from the earthing element (Rx) to the auxiliary earthing rod H(C)
and check whether or not there is an almost at section shown in (b)
in the measured resistance even though the auxiliary earthing rod
S(P) has been moved.
If no at section is seen, the measurement distance is insufcient.
Move the installation locations of the auxiliary earthing rods (S(P)
and H(C)) to further locations.