Earthing Resistances Measurement - Fluke 1625-2 User Manual

1625-2
Users Manual

Earthing Resistances Measurement

This instrument is equipped with a 3-pole as well as a 4-pole resistance measurement
that renders measurements of resistances of earthing systems possible, as well as
measurements of the soil resistivity of geological strata. A specific description of the
different applications is given further on in this manual. As a special function, the
instrument offers measurements with an external current transformer, with which a
measurement of single resistance branches in interlinked networks (lightning protection
and high voltage pylons with cabling) can be performed without separating parts of the
system. See Figure 3.
To ensure most feasible interference suppression during measurements, the instrument
is equipped with four measuring frequencies (94 Hz, 105 Hz, 111 Hz, 128 Hz), with
automatic switch over if necessary (AFC - Automatic Frequency Control). The
corresponding measuring frequency used for a specific measurement can be called and
displayed with DISPLAY MENU after the measurement. Additionally, one of the four
measuring frequencies can be selected and permanently set in special cases. In that
case, in order to stabilize the display, an average measurement can be carried out for up
to 1 minute by keeping the START TEST button pressed.
To determine the earthing impedance (R*) a measurement with a frequency close to the
mains frequency (55 Hz) is carried out. At the activation of R* through user's code, this
measuring frequency is activated automatically.
To keep the instrument as simple as possible at the time of delivery, all special functions,
such as LIMIT input, BEEPER programming, and measurement of earthing impedance
(R*) are not activated at delivery. They can be activated with personalized user's code
(see How to Change All Data Settings with Personalized CODE).
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Figure 3. Method for Earthing Resistances Measurement
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