Ground Resistance Tester Model 6471
21
3.2.6 Soil Resistivity Measurement
ρ
Measuring method:
Voltage/Current measurement (EN 61557 part 5)
Open circuit voltage:
16 or 32Vrms square wave
Test frequency:
Selectable from 41 to 128Hz (see table in § 6.2)
Short circuit current:
> 200mA
AC
Noise suppression:
> 80 dB for frequencies 20% or more above or below the
test frequency
Max. overload:
250Vrms
Max. value for R
H
, R
S
, R
ES
, R
E
:
100k
Ω
Calculation formula, Wenner:
ρ
W
= 2
p
d R
S-ES
Calculation formula, Schlumberger:
ρ
S
= (
p
(d2 - (A/2)²) / A) R
S-ES
Maximum value of
ρ
:
999k
Ω
m (display in k
Ω
ft is not possible)
Measuring time:
Short push on START:
approx. 8 s for first value of R
S-ES
at
128 Hz, then 3 measurements per s.
Long push on START:
approx. 20 s for first value of R
S-ES
at
128 Hz, then 3 measurements per s.
Measurement
Range
0.00 to
9.99
Ω
10.0 to
99.9
Ω
100 to
999
Ω
1.00 to
9.99k
Ω
10.0 to
99.9k
Ω
Resolution
0.01
Ω
0.1
Ω
1
Ω
10
Ω
100
Ω
Intrinsic error
± (2% + 1ct)
The intrinsic error specified refers to reference conditions with a test voltage of
32V, test frequency of 128Hz, R
ρ
-H
, R
ρ
-S
, R
ρ
-ES
and R
ρ
-E
= 1k
Ω
, no external voltage.
Operating conditions : R
S-ES
< 3 x R
ρ
-H
and:
Operating error for R
S-ES
R
electrode
≤
100k
Ω
R
electrode
/ R
S-ES
≤
2000
± (7% + 2cts)
R
electrode
≤
50k
Ω
R
electrode
/ R
S-ES
≤
10,000
± (15% + 3cts)
R
electrode
≤
10k
Ω
R
electrode
/ R
S-ES
≤
20,000
± (20% + 1ct)
R
rod
is the resistance of the earth rods R
ρ
-E
, R
ρ
-ES
, R
ρ
-E
, R
ρ
-H
assumed to be identi
-
cal.
Note:
With a test voltage U
OUT
of 16V, halve the value of R
rod
.
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