Recommendations For A Reliable Measurement - AEMC 6471 User Manual

5.4.3
Moving the Auxiliary Electrodes
Move electrode S (Y) towards electrode H (Z) by a distance equal to 10% of d and
make another measurement. Then move electrode S (Y) again by a distance equal
to 10% of d, but towards the earth electrode.
The 3 measurement results should be the same to within a few percent. If this is
the case, the measurement is valid.
If not, electrode S (Y) is in the zone of influence of the earth electrode. It will be
necessary to increase distance d for the H (Z) auxiliary electrode and repeat the
measurements.
Positioning of the Auxiliary Electrodes
To make sure that your earth measurements are not distorted by interference, we
recommend repeating the measurement with the auxiliary electrodes placed at a
different distance and in another direction (for example, rotated 90° from the first
alignment).
If you find the same values, your measurement is reliable. If the measured values
are substantially different, it is likely that they were influenced by earth currents or
a groundwater source. It may be useful to drive the electrodes deeper and/or wet
the ground near them to reduce their contact resistance with the soil.
Avoid routing the connecting cables of the earth electrodes near or parallel to other
cables (transmission or supply), metallic conductors, rails, or fences: high test fre-
quencies may cause cross-talk and affect the measurements.
Ground Resistance Tester Model 6471
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Recommendations for a Reliable Measurement

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