Noise voltages present at ground connections may
influence the measurement result. Noise voltage in-
fluence is very low for the instrument TELARIS
EARTH. 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 guar-
anteed.
During automatic frequency selection mode,
TELARIS EARTH selects the measurement fre-
quency with the lowest, measured interference volt-
age. Only use manual frequency selection, if the
noise frequency is known. If noise voltages are pre-
sent influencing the measurement result in spite of
the filter, this condition is shown by displaying "Un-
oise".
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) ex-
ceeds the value 1000/1 (10000/1), the measure-
ment accuracy indicated in the technical data sec-
tion does no longer apply for the TELARIS ERDE.
This is caused by the fact that the voltage to be mea-
sured only amounts to 1/1000 (1/10000) of the volt-
age 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 connec-
tion or earth rod contact to the surrounding earth
(e.g. inserting earth rods deeper into the ground,
humidify earth or use earth rods parallel around
earth rods).
Technical Terms
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 suf-
ficiently distant from the respective ground such
that no noticeable voltages, caused by the ground-
ing current, occur at any point within this range.
Auxiliary earth electrode (H): Additional earth
probe leading the measurement current for mea-
surement purposes.
Probe (S): An additional earth probe, preferably an
earth rod, which is used as a potential for the ref-
erence earth for measurement purposes.
Speading resistance of a earth: The resistance of
the earth between earth and reference earth.
22
General Information concerning Earth Measurement
PTDB89860000.qxd 02.03.2006 11:32 Uhr Seite 22
