Besantek BST-MGR01, Инструкция по эксплуатации

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Measuring the earth mat connections resistance.
The Earth mat connections resistance is done using the 4 wires
method, to ensure accuracy of these low resistance.
The earth mat is connected using very low resistance connections to
ensure fault current are passed without or very little resistance.
It is very important to measure these connections, using the 4 wires
methods, to ensure added accuracy and remove errors from the
test leads. Earth mat rely completely on good connections and low
resistance for their effectiveness. Their regular testing and correct
measurement will ensure proper working of the protection systems.
13. Working Principle of The Instrument
This Test Instrument has a regulated current source which injects its
regulated DC current into the low resistance to measure.
The current is injected into the resistance under test through the
terminals C1 and C2.
This Test Instrument has a DC voltmeter which measure the DC
voltage across the resistance to be measured.
The Voltmeter connections are on P1 and P2.
The display shows a number proportional to the ratio of the current
injected and the voltage measured. R=U/I
When the user change the range of the instrument, the current
regulation change, from 10mA to 1A, according to the user selection.
The current selected is shown on its corresponding LED, on the left
of the facia.
When selecting a current, the range is automatically selected by the
processor.
So, selecting a current and a range has the same function and is
using one push button.
The Instrument is processor driven and the software takes care of
the different switching elements inside the circuit.
The product has protection against over-voltage and over-
temperature.