MRU-200-GPS OPERATING MANUAL Version 1.06
57
10.2.7 Influence of interference current upon the result of the earth re-
sistance measurement using double clamps
The MRU-200 meter may perform a measurement if the value of the interference current does
not exceed 3A rms and the frequency complies with the value set in the MENU.
R
E
Uncertainty [
Ω]
0.00 to 4.99
Ω
within the range of the basic uncertainty
5.00 to 19.9
Ω
)
10
5
(
3
2
3
zakl
E
I
R
20.0 to 149.9
Ω
)
10
6
(
3
2
2
zakl
E
I
R
If the interference current exceeds 3A the possibility of measurement is blocked.
10.2.8 Influence of the relation of the resistance measured with clamp for
the multiple earthing branch to the resultant resistance (3P + clamp)
R
C
Uncertainty [
Ω]
≤99.9Ω
)
10
3
(
2
3
w
C
R
R
>99.9
Ω
)
10
6
(
2
2
w
C
R
R
R
C
[Ω] is the value of the resistance measured with clamps for the branch displayed by the device,
and R
W
[Ω] is the value of the resultant multiple earth resistance.
10.2.9 Additional uncertainties in accordance with IEC 61557-4 (2P)
Influencing factor
Symbol
Additional uncertainty
Location
E
1
0%
Power supply voltage
E
2
0% (
not displayed)
Temperature
E
3
R
≤3.999Ω
±0.3digits/°C
R>3.999
Ω and
<1k
Ω
±0.2digits/°C
R≥1kΩ
±0.07%/°C
±0.2 digits/°C
10.2.10 Additional uncertainties in accordance with IEC 61557-5 (3P, 4P,
3P + clamp)
Influencing factor
Symbol
Additional uncertainty
Location
E
1
0%
Power supply voltage
E
2
0% (
not displayed)
Temperature
E
3
R
≤3.999 Ω
±0.3digits/°C
R>3.999
Ω and
<1k
Ω
±0.2digits/°C
R≥1kΩ
±0.07%/°C
±0.2 digits/°C
Serial interference voltage
E
4
In accordance with formula In
10.2.1 (V
z
=3V 50/60/400/16 2/3Hz)
Resistance of electrodes and
auxiliary earth electrodes
E
5
In accordance with the formula in
10.2.3
