General Information Concerning Earth Measurement - PEWA UNITEST TELARIS ERDE Mode D'emploi

Prior to usage, inspect electronic load for external damage.Prior to any operation,
ensure that the connecting leads used and the electronic load are both in perfect
condition.
If the operator's safety can no longer be guaranteed, the instrument is to be put out of
service and protected against use. The safety is no longer guaranteed, if the
instrument:
• shows obvious damage
• does not carry out the desired measurements
• has been stored for too long under unfavourable conditions
• has been subjected to mechanical stress during transport.
The instrument may only be used within the operating ranges as specified in the
technical data section.
Avoid any heating up of the instrument by direct sunlight to ensure perfect functioning
and long instrument life.
The opening of the instrument for fuse replacement, for example, may only be carried
out by professionals. Prior to opening, the instrument has to be switched off and dis
connected from any current circuit.

4.0 General Information concerning Earth Measurement

(also refer to term descriptions page 18)
The measurements are carried out independent from the mains as power is supplied by
the built in batteries. Earth resistance is determined by means of a current-voltage measu-
rement procedure. Grounding is an important part of a power supply system. It is requi-
red to bring the individual system parts and current circuits to a common reference
potential, in proximity to the reference ground. Grounding is also used to protect systems
from overvoltages or short-circuit currents. Earth resistance must be of sufficiently low
resistance. Thresholds are defined within the VDE regulations. Grounding or grounding
resistance is composed of ground conductor (equipotential bonding conductor or PE), the
ground (foundation ground, earthing rod, band ground...), and the earth diffusion resi-
stance. This represents the resistance between ground and reference ground. A voltage
funnel is formed around any ground. The shape depends on the ground itself and the sur-
rounding earth. Assuming a regular earth composition of similar temperature and
humidity, the voltage funnels around the ground are of concentric shape. The lower the
earth resistance, the smaller the voltage funnels. For grounding measurement, the voltage
drop that is being measured is generated by a known, constant current across the gro-
und resistance to be measured.
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