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GMC-I Messtechnik GmbH
6
Testing Devices in Accordance with DIN VDE 0701-0702
Always measure protective conductor resistance first for safety class I devices under test.
Measurement of insulation resistance, equivalent leakage current and protective conductor
current is not possible without a properly functioning protective conductor. This
measurement is of special importance because a defective or reversed protective conductor
may represent a hazard for the user!
Note!
Please note that the display indicates overloading when measuring protective
conductor resistance and insulation resistance, if the terminals are open or if the
upper range limit is exceeded. Only “O.L” appears at the display in this case.
Note!
The limit values specified in the following sections correspond to the current status at
the time or printing. Please note that normative legislation is continuously updated to
meet the safety requirements necessitated by changing market situations, and that
the listed limit values are thus subject to change.
6.1
Measuring Protective Conductor Resistance for Protection Class I Devices
Connect the single-pole probe cable with test probe and clip (21) to the housing of the DUT
in accordance with section 5.1. Assure good contact. In the case of stationary DUTs,
measurement can be performed without interrupting the mains connection. To this end,
connection must first be established from the protective conductor socket (4) at the METRA-
TESTER 5+ to a protective conductor which has been previously tested for the absence of
voltage – for example at an outlet within the electrical system – which is
connected with the protective conductor of the DUT. When testing in accordance with
DIN VDE 0701-0702, DUTs with external connections such as data cables etc. can be
tested within their entire configuration at the installation site (see section 5.4 regarding
connection).
However, due to the fact that this test does not provide any indication as to the safety of the
device under test, complete testing via the connector sockets at the test case must be
performed as soon as disconnection from the mains and the connector cables is possible –
insofar as permitted by the device.
Ð
Set the measuring function selector switch (6) to the “20 Ohm” range.
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Read the measured value in Ohms at from the LCD panel, and compare it to permissible
values in accordance with DIN VDE 0701-0702.
Protective conductor resistance may not exceed the following resistance values:
Maximum Permissible Values for Protective Conductor Resistance Relative to Cable Length
(per DIN VDE 0701-0702:2008)
A value of 1
Ω
may not be exceeded on any case. The table applies to cable reels and extension cables
as well.
In the case of longer cables, 0.1 Ohms is added per additional 7.5 m cable length regardless
of conductor cross-section.
Lengths up to [m]
5
12.5
20
27.5
35
42.5
50
More than 50
Max. resistance [
Ω
]
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0