If many tests of mains internal resistance, loop
impedance, or RCD are carried out allowing
only brief pauses, the internal over temperatu-
re protection of the UNITEST 0100-ELECTRO-
check will respond and the ’Over temperature’
symbol (9) is displayed. The next test may only
be carried out after the instrument has cooled
down and after the ‘Over temperature’ symbol
has disappeared from the display. Thus, the in-
strument will not be damaged.
(FAT) measurements must be carried out in
compliance with the respectively valid stan-
dards and regulations.
For further information or reference regarding
the performance of measurements, we kindly
ask you to refer to our ’Measurement Booklet’,
which is available at no charge from our servi-
ce department or our distribution partners.
To answer further questions regarding the ap-
plication of DIN/VDE regulations and regarding
the performance of measurements, we furt-
hermore offer special practical training cour-
ses. It will be our pleasure to send you further
detailed information if requested. Please do not
hesitate to contact us.
5.1 Low Impedance Measurement
This test is used to check protective conductors,
ground conductors, and equipotential bonding con-
ductors for low impedance continuity. Opening the
bridge between PE and N is also used to detect
wrongly connect sockets (N and PE reversed). The
low impedance measurement is always used, when
low impedance connections between protective
conductors and equipotential bonding conductors
must be checked.
The test is carried out using DC current of >200 mA
and a test voltage of approx. 4-7 V.
Prior to any test it must be ensured that the sys-
tem parts to be tested are not live.
If a voltage exceeding approx. 5...25V is pre-
sent at the test leads the symbols ”
” (14)
and 'Uext' (17) are indicated on the LCD. Ad-
ditionally, an acoustic signal is audible when
starting the test.
The test result may be impaired by galvanic el-
ements within the system to be tested due to
the polarity of the test current applied. There-
fore, the test should always be repeated by ap-
plying reverse polarity. Simply swap the two
measurement connections L/L1 (24), N/L2
(25) at the UUT or the test instrument. The rea-
son for a different test result for the second re-
verse polarity test could be corroded connec-
tions or transition resistances.
Impedances of additional operational current
circuits switched in parallel or transient cur-
rents can result in erroneous measurement re-
sults.
10
Low Impedance Measurement
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