HT instruments MACROTEST G3 - Manual (Page 104)

MACROTESTG3 - COMBIG3
EN - 103
If the length of the cables supplied with the instrument is not enough, you can create your
own extensions to carry out the measurements in the system without influencing the
instrument accuracy and, by the nature of the voltammetric method, without the need to
perform any compensation of measuring cable resistance.
To create extensions, always adopt the following guidelines to ensure the safety of the
operator:

Always use cables characterized by insulation voltage and insulation class appropriate
to the rated voltage and measurement category (overvoltage) of the system under
consideration.
 For extension terminals, always use connectors having measurement category
(overvoltage) and voltage appropriate for the point where you plan to connect the
instrument (see § 1.4). The use of the optional accessories 1066-IECN (black) and
1066-IECR (red) is recommended.
Method for small-sized earth networks
Let a current stream between the earth network under test and an auxiliary rod placed at a
distance equal to fivefold the diagonal of the area limiting the earth installation itself
(see Fig. 37). Place the voltage probe at approximately half way between the earth rod
and the current probe, finally measure the voltage between them.
Fig. 37: Ground measurement for small-sized earth networks
If needed, use multiple probes in parallel and wet the surrounding ground (see Fig. 37) if
the instrument is not able to supply the current required to perform the test due to a high
resistance of the ground.
Big-sized earth networks
This technique is always based on the voltammetric method and is used where it is difficult
to position the auxiliary earth current rod at a distance equal to 5 times the diagonal of the