―
15
―
7. Measuring method
7.1 Measuring protective conductor resistance (RPE)
The measurement of protective conductor resistance is of course not possible
for devices which are not equipped with a protective conductor (e.g. Safety
Class ll and III devices).The objective of this test is to ensure the connection
between the earth or the protective conductor of the commercial power earth
pin and the metal casing and accessible conductive parts of the DUT is
satisfactory and of a low enough resistance value to satisfy safety standards.
And this measurement should be done also by reversing the output polarity.
(1) Connect the DUT as described in clause 6.
(2) Set the range switch to the "RPE 20
Ω
+" position.
(3) Read the measured value in "
Ω
" from the LCD.
(4) Set the range switch to the "RPE 20
Ω
-" position.
(5) Move the cable from the DUT during a measurement, section by
section over its entire length, in order to locate interruptions.
Results
Protective conductor resistance may not exceed the following values.
Maximum allowable protective conductor resistance values depending on
cable length
Under no circumstances may a value of 1
Ω
be exceeded. The table is also
valid for cable reels and extension cables.
CAUTION
●
Follow the procedure described in 5.2-4 and do NULL setting before a
measurement.
●
Alligator clip must make good contact with the enclosure of the DUT.
●
When the terminal is open or the resistance value exceeds measuring
range, "OL" mark (over range display) appears on the LCD.
！
Length to (m)
Max. resistance (
Ω
)
5
0.3
12.5
0.4
20
0.5
27.5
0.6
35
0.7
42.5
0.8
50
0.9
More than 50m
1.0
Displayed on 20
Ω
+ range
Displayed on 20
Ω
- range
Displayed at NULL
setting
Fig.14
