LEM A188506510, Руководство по эксплуатации

Страница: 10 / 66

8
Measurement of earthing resistance (RE)
The earthing resistance is determined by a 3- or 4-pole current and voltage
measurement. The measuring voltage is a square pulse AC voltage with 48 / 20 V
and a frequency of 94 ,105 , 111 or 128 Hz. The frequency can be selected manually
or automatically (AFC) .
Selective measurement of earthing resistance* (RE )
Measurement of a single earth electrode in a mesh operated (parallel) earthing
system. The current flowing through the single earth electrode is measured with an
external current transformer.
Resistance measurement (R~)
The resistance is determined by a 2 pole current and voltage measurement. The
measuring voltage is a square pulse AC voltage with 20 V and a frequency of 94,
105, 111 or 128 Hz. The frequency can be selected manually or automatically (AFC).
Low resistance measurement (R
...
)
The resistance is determined by DC current and voltage measurement. 2- as well as
4-pole measurement is possible. The short circuit current is > 200 mA. The
resistance of both current directions is measured and stored.
Checking for correct measuring connection
Via split socket and following detection circuit, the processor checks if the measuring
lead is properly connected according to the selected function. A wrong or missing
connection is indicated by an optical or acoustical signal.
Beeper
The built in beeper has two functions:
1.
Giving messages if set limit values are exceeded.
2. Indicating dangerous conditions or maloperation.
Controlling is done by means of the microprocessor.
LO-BAT
Supervision of the battery charge status is done with a comparator circuit. Via
microprocessor, a drop in battery capacity down to typ. 10 % of its specified value is
indicated on the display with symbol
LO-BAT .
* Patent applied for.