Amprobe Telaris-Earth-Test Earth-Resistance-Tester - Manual (Page 11)

Noise voltages present at ground connections may influence the measurement result. Noise
voltage influence is very low for the instrument EARTH-TEST. A precise filter suppresses all
interference whose frequencies are different with respect to the respective measurement
frequency. Together with the possibility to choose between two measurement frequencies,
best measurement results can be guaranteed. During automatic frequency selection mode,
EARTH-TEST selects the measurement frequency with the lowest, measured interference
voltage. Only use manual frequency selection, if the noise frequency is known. If noise
voltages are present influencing the measurement result in spite of the filter, this condition
is shown by displaying "Unoise". Further influence on measurement accuracy is emitted by
ratios RH/RE and RS/RE, or absolute value of RH and RS. If the ratio RH/RE (RS/RE) exceeds the
value 1000/1 (10000/1), the measurement accuracy indicated in the technical data section does
no longer apply for the Amprobe EARTH-TEST. This is caused by the fact that the voltage to
be measured only amounts to 1/1000 (1/10000) of the voltage present within the
measurement circuit. If the ratio RH/RE (RS/RE) becomes excessive, "
Limit RH “RS“ is
shown in the display. The user should try to realise a better ground connection or earth rod
contact to the surrounding earth (e.g. inserting earth rods deeper into the ground, humid
earth or use earth rods parallel around earth rods).
Technical Terms:
9
Earth (E): The ground is a conductor within the earth or a
foundation being in conductive connection with the
earth (e.g. a foundation ground in concrete).
Earth probe (ES) Connector of earth rod next to the earth connecter.
Reference ground: An area of the earth that is sufficiently distant from the
respective ground such that no noticeable voltages,
caused by the grounding current, occur at any point
within this range.
Auxiliary earth electrode (H): Additional earth probe leading the measurement current
for measurement purposes.
Probe (S): An additional earth probe, preferably an earth rod,
which is used as a potential for the reference earth for
measurement purposes.
Spreading resistance of a earth: The resistance of the earth between earth and reference
earth.
PAEB30872261:Layout 1 12.12.2007 12:06 Uhr Seite 9