Fluke 1625 FE 1625 Users Manual - Page 43

pole measurement with longer earth electrode connecting leads, Time average measurement

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Earth/Ground Tester Procedure of Measurements An accuracy test of the results is made with another measurement following repositioning of the auxiliary earth electrode or probe. If the value stays the same, the distance is sufficient. If the measured value changes, probe or auxiliary earth electrode must be repositioned until the measured value RE stays constant. Spike wires should not run too close to each other. 3-pole measurement with longer earth electrode connecting leads Use one of the accessory cable drums as earth electrode connecting lead. Spool off cable completely and compensate line resistance as described in "Compensation of Earth Electrode Connecting Lead". Time average measurement: If there is a warning "measured value unstable" (see "Procedures of Measurement", "Description of display") after a test sequence, most likely it is caused by strong interference signals (e.g. unsteady noise voltage).Nevertheless, to get reliable values, the instrument offers the possibility of averanging over a longer period. 1. Select a fixed frequency (see "Control loop" in "Operation") 2. Keep the "START TEST" button pressed until the warning "measured value unstable" disappears. Max. averaging time is approx. 1 min. Evaluation of measured value: Figure 10 shows the maximum permissible value of the Earth resistance which will not exceed a permissible limit value, taking into account the maximum usage error. 0 10 Desired Values 20 50 100 200 500 1000 3000 3152 5 10 20 50 100 200 500 1000 2000 2999 Measured Values edw013.eps Figure 10. Earth Resistance - Maximum Permissible Value 35

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Earth/Ground Tester
Procedure of Measurements
35
An accuracy test of the results is made with another measurement following
repositioning of the auxiliary earth electrode or probe. If the value stays the
same, the distance is sufficient. If the measured value changes, probe or auxil-
iary earth electrode must be repositioned until the measured value R
E
stays
constant.
Spike wires should not run too close to each other.
3-pole measurement with longer earth electrode connecting leads
Use one of the accessory cable drums as earth electrode connecting lead. Spool
off cable completely and compensate line resistance as described in “Compen-
sation of Earth Electrode Connecting Lead”.
Time average measurement:
If there is a warning "measured value unstable" (see “Procedures of Measure-
ment”, “Description of display”) after a test sequence, most likely it is caused
by strong interference signals (e.g. unsteady noise voltage).Nevertheless, to get
reliable values, the instrument offers the possibility of averanging over a
longer period.
1.
Select a fixed frequency (see “Control loop” in “Operation”)
2.
Keep the "START TEST" button pressed until the warning "measured
value unstable" disappears. Max. averaging time is approx. 1 min.
Evaluation of measured value:
Figure 10 shows the maximum permissible value of the Earth resistance which
will not exceed a permissible limit value, taking into account the maximum
usage error.
0
5
10
10
20
20
50
50
100
100
200
200
500
500
1000
1000
2000
2999
3000 3152
Desired Values
Measured Values
edw013.eps
Figure 10. Earth Resistance - Maximum Permissible Value