Measurement methods
• Impulse method – measurement of lightning protection systems with a measuring
impulse ramp of 4/10 μs, 8/20 μs, 10/350 μs
• 3-pole and 4-wire method – measurement of earthing systems using auxiliary
probes
• 3-pole method with clamp – measurement of earthing systems with multiple
earth electrodes
• Two-clamp method – measurement of earthing system when the auxiliary
probes cannot be used
• Earth resistivity – Wenner method
• Resistance of earth connection and equipotential bonding measured
using current ≥200 mA with auto-zero function – meets the requirements
of EN 61557-4
• Measurement of leakage current
Additional features
• MRU-200-GPS | Built-in GPS receiver – recording results with location
coordinates
• Measurement of resistance of auxiliary electrodes RS and RH • Measurement of interference voltage
• Measurement of interference frequency
• Measurement in the presence of interference voltage generated by power
networks with frequency of 16 2/3 Hz, 50 Hz, 60 Hz, 400 Hz
• Selection of maximum measuring voltage (25 V and 50 V)
• Automatic calculation of soil resistivity in ohm-meters (Ωm) and ohm-feet (Ωft)
• Memory of 990 measurement results (10 banks of 99 cells each)
• Calibration of clamp used
• Real time clock (RTC)
• Data transmission to the computer and mobile devices
• Battery indication
Application
MRU-200 and MRU-200-GPS meters were created for the most difficult working
conditions. They generate a measuring current exceeding 200 mA, which
provides effective measurements of grounding of energy objects such as
transformer stations and power stations.
Thanks to the methods using clamps, it is not necessary to disconnect the
control connectors, which is sometimes a very tedious operation. This plays a
special role when performing works on objects exposed to weather conditions,
where the connecting elements are sometimes corroded or tarnished.
The graphical user interface provides clear readings and explicit messages.
This translates into quick, trouble-free service.
Impulse method
MRU-200 and MRU-200-GPS may be used to test earthing of lightning protection
systems, as these meters are able to simulate the conditions occurring
during a lightning strike – they generate currents with a standardized pulse
leading edge and a time to half-peak. Available impulse ramps include 4/10 μs,
8/20 μs, 10/350 μs.
Compatible with ERP-1 adapter
ERP-1 adapter allows user to test earthing systems using flexible clamps.
This is particularly useful, e.g. in case of lattice towers – there is no need to
switch off the line or disconnect control connectors. Proprietary algorithm allows
user to check the current direction in the individual measurements and
facilitates damage detections, e.g. corroded steel strip (hoop).
Memory and results
The results can be saved to the device’s memory. It is divided into 10 banks
of 99 cells, each corresponding to one measurement. These results can be
easily transferred to the Sonel Reader software for archiving or subsequent
analysis and research.
Bluetooth wireless interface may be used to transfer measurement results to
PC software or to a mobile phone with dedicated app – Sonel MRU Mobile.
This provides not only data archiving function, but further data transfer – directly
from the measurement site via an e-mail.
Capabilities
The measuring methods available in the device allow for comprehensive control
of working and protective grounding. The calibration function of the test
leads eliminates the influence of their resistance on the result. However, this is
just the beginning.
• The 4-wire method provides very accurate measurement of the expected
small values of resistance – eliminates the resistance of the test leads connecting
the meter to grounding.
• Measurement of resistance of earth connection and equipotential bonding
with a current exceeding 200 mA meets the requirements of EN 61557-4 standard.
• Before performing the measurement, the meter checks whether the tested
object is a subject to excessive interference voltage, which may indicate additional
problems.
Technical specifications
Measurement functions Measurement
range
Display
range Resolution Accuracy
±(% m.v. + digits)
Interference voltage 0 V…100 V 0 V…100 V 1 V ±(2% m.v. + 3 digits)
Resistance of earth connection
and equipotential bonding
0.045 Ω…19.99 kΩ
acc. to EN 61557-4
0.000 Ω…19.99 kΩ from 0.001 Ω from ±(2% m.v. + 2 digits)
Earth resistance
3-pole and 4-wire method
0.100 Ω…19.99 kΩ
acc. to EN 61557-5
0.000 Ω…19.99 kΩ from 0.001 Ω from ±(2% m.v. + 2 digits)
3-pole + clamp method
0.120 Ω…1999 Ω
acc. to EN 61557-5
0.000 Ω…1999 Ω from 0.001 Ω ±(8% m.v. + 3 digits)
two-clamp method 0.00 Ω…149.9 Ω 0.00 Ω…149.9 Ω from 0.01 Ω from ±(10% m.v. + 3 digits)
impulse method
4/10 μs, 8/20 μs, 10/350 μs pulse
0.0 Ω…300 Ω 0.0 Ω…300 Ω from 0.1 Ω from ±(2.5% m.v. + 3 digits)
auxiliary electrodes resistance 0 Ω…19.9 kΩ 0 Ω…19.9 kΩ from 1 Ω ±(5% (RE+RH+RS) + 8 digits)
Earth resistivity 0.0 Ωm…999 kΩm 0.0 Ωm…999 kΩm from 0.1 Ωm
Depends on the accuracy of the
RE 4p measurement. but not less
than ±1 digit
Leakage current 0.1 mA…300 A 0.1 mA…300 A from 0.1 mA from ±(5% m.v. + 5 digits)
Safety and work conditions
Measuring category according to EN 61010 III 600 V / IV 300 V
Ingress protection IP54
Type of insulation according to EN 61010-1 and IEC 61557 double
Dimensions
288 x 223 x 75 mm
11.3” x 8.8” x 3.0”
Weight
ca. 2 kg
ca. 4.4 lbs
Operating temperature
-10…+50°C
14…122°F
Storage temperature
-20…+80°C
-4… 176°F
Humidity 20…90%
Nominal temperature
23 ± 2°C
73.4°F ± 3.6°F
Reference humidity 40%…60%
Memory and communication
Memory of measurement results 990 results
Data transmission USB, Bluetooth
MRU-200-GPS | GPS position accuracy 3 m
Other information
Quality standard – development, design and production ISO 9001
The product meets the EMC (emission for industrial environment)
requirements according to standards
EN 61326-1
EN 61326-2-2
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