Fluke 1625 FE 1625 Users Manual - Page 52

Compensation of Earth Electrode Connecting Lead, Measuring process

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1625 Users Manual Example: Your clip-on transformer has a transformation ratio of tr = 1000:1. The measurement without clip-on transformer results in a value RE = 0.983 Ω . With a clip-on transformer a value of RE = 1.175 Ω is measured. The deviation thus reads (1.175 - 0.983) Ω= + 0.192 Ω and referring to RE = 0.983 Ω an error evolves as following: 100% × 0.192Ω = +19.5% 0.983Ω The new transformation ratio to be set calculates: trnew = 1000 × 1.175 = 1195 0.983 Compensation of Earth Electrode Connecting Lead If the line resistance to the earth electrode can not be ignored, a compensation of the connecting lead resistance to the earth electrode is possible. Proceed as described below: Measuring process: START TEST 1625 EARTH / GROUND TESTER H /C2 DISPLAY MENU Earth/Ground Resistance 300 k RA CHANGE ITEM 4 POLE 3 POLE 4 POLE 3 POLE AC Resistance 300 k R DC Low Resistance 3k R 2 POLE 2 POLE 4 POLE SELECT OFF S/P2 ES/P1 E /C1 Earth electrode Auxiliary earth electrode edw019.eps Figure 15. Compensation of Earth Electrode Connecting Lead 1. Turn central rotary switch to position "RE 3pole". 2. Wire instrument according to picture. 44

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1625
Users Manual
44
Example:
Your clip-on transformer has a transformation ratio of tr = 1000:1. The meas-
urement without clip-on transformer results in a value R
E
= 0.983
Ω
. With a
clip-on transformer a value of R
E
= 1.175
Ω
is measured.
The deviation thus reads (1.175 - 0.983)
Ω
= + 0.192
Ω
and referring to R
E
=
0.983
Ω
an error evolves as following:
%
5
.
19
983
.
0
192
.
0
%
100
+
=
Ω
Ω
×
The new transformation ratio to be set calculates:
1195
983
.
0
175
.
1
1000
=
×
=
trnew
Compensation of Earth Electrode Connecting Lead
If the line resistance to the earth electrode can not be ignored, a compensation
of the connecting lead resistance to the earth electrode is possible. Proceed as
described below:
Measuring process:
R
RA
R
Earth/Ground Resistance 300k
AC
Resistance
300k
DC Low Resistance 3k
CHANGE
ITEM
SELECT
START
TEST
DISPLAY
MENU
H/C2
S/P2
ES/P1
E/C1
4
POLE
3
POLE
4
POLE
2
POLE
2
POLE
4
POLE
OFF
3
POLE
EARTH / GROUND TESTER
1625
Auxiliary
earth
electrode
Earth
electrode
edw019.eps
Figure 15. Compensation of Earth Electrode Connecting Lead
1.
Turn central rotary switch to position "R
E
3pole".
2.
Wire instrument according to picture.