With the use of the presented earth resistance and soil
resistivity meter Sonel MRU-120 it is possible to carry out
earth resistance measurements using 3-pole and 4-wire method,
measurements with the use of additional clamps (multiple earthing -
without the necessity of unfastening the monitoring connections), as
well as measurements using two-clamp
method - in some cases it is possible to carry out the measurement
without the necessity of using auxiliary probes driven into the
ground. Sonel MRU-120 is a device designed
to meet the needs of the power industry and used for earthing
measurements - measuring range (measurements in accordance with EN
61557 standard) from 0.30 Ω. The functionality
of the device is completed by the possibility to measure the
resistivity of soil and the continuity of protective and equalising
connections.
Measurement methods
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
Soil 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
Additional features
Measurement current of 200 mA –
facilitates earth resistance measurements in difficult areas
(sand, stony soil)
Measurement of resistance of auxiliary
electrodes RS and RH
Measurement of interference voltage
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 was created for the most difficult working
conditions. It generates 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.
Protection and equipment
Housing of MRU-120 ensures safe operation in field conditions and
inside buildings. Ingress protection rating of IP54 protects the
device
against water and solids in case of splashes or dusty conditions.
Moreover, the design of the device provides very good protection
during
transport and handling. Extensive standard equipment allows user to
perform most measurements without the need to purchase additional
accessories. MRU-120 is a versatile solution that offers
comprehensive testing of earthing systems.
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 four-lead 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 the continuity of protective
connections and equipotential bondings 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.
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.
Other useful functions
Built-in help function – auxiliary illustrations demonstrate
how to properly perform the measurement for each method.
Correctness of connections – if the meter detects an error,
which prevents a correct measurement, it will indicate this in the
top of the screen using the appropriate test socket symbol.
Complete measurement data – in addition to earth resistance
measurement, the device performs additional measurements on
interference voltages and resistance of auxiliary probes.
Their results are provided with information about the date and time
of testing, which facilitates preparing test documentation.
