MRU-200
Catalog index: WMGBMRU200
Earth Resistance & Resistivity Meter
Multifunctional earthing and soil resistivity meter
The Sonel MRU-200 earth resistance and soil resistivity meter for earth resistance and soil resistivity measurements with the use of various methods.
The feature that definitely distinguishes this model from other meters of this kind is the use of all known methods of earth resistance measurement. The measurement can be carried out using the technical 3-pole and 4-wire method, also with additional clamps (multiple earthing), as well as the two-clamp method and the impulse method (earthing impedance measurement).
The use of the two-probe method allows the testing to be carried out without the need for additional auxiliary probes which are driven into the ground. The impact method, on the other hand, is used, among other things, to diagnose lightning protection earthing. It is also used for extensive, multiple and bonded earthing measurements (also underground). The advantage of this method is that there is no need to tamper with the circuit. The impact method enables measurements to be made in accordance with EN 62305 - the need to measure earth impedance.
This is not the end of the extended capabilities provided by the Sonel MRU-200 meter. The device additionally has the function of measuring the resistivity of soil, the continuity of protective and equalising connections, and, with the use of clamps, also leakage or fault currents.
Apart from the large number of functions and many measurement possibilities, the MRU-200 meter deserves recognition also for the high accuracy of the obtained results. Measuring range - measurements in accordance with EN 61557 - from as low as 0.30 Ω.
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 and compensatory conductors measured using current ≥200 mA with auto-zero function – meets the requirements of EN 61557-4
- Measurement of leakage current
Additional features
- 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 meter 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.
Impulse method
MRU-200 may be used to test earthing of lightning protection systems, as this meter is able to simulate the conditions occurring during a lightning strike – it generates current 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).
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.
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.
Specification
It allows to take the measurements of:
- earth resistance using auxiliary electrodes,
- earth resistance using auxiliary electrodes and clamp (for measurements of multiple earthing)
- earth resistance using double clamps (for measurement of earthing when it is impossible to use auxiliary electrodes),
- impulse earth impedance (without disconnecting measured earthing),
- ground resistivity (Wenner method),
- current using the clamp (e.g. leakage) and flexible clamp (Rogowsky coil),
- measurement of continuity of equipotential bondings and protective conductors (meeting the requirements of IEC 60364 – 6 – 61:2000 section 6.12.2) with auto-zero function – with current 200 mA.
Additionally:
- measurement of resistance of auxiliary electrodes RS and RH,
- measurement of interference voltage,
- measurement of interference frequency,
- measurement in the presence of interference voltage in the power network
with frequency 16 2/3 Hz, 50 Hz, 60 Hz and 400 Hz (with automatic selection of proper frequency of measuring signal or with manual selection), - selection of maximum measuring voltage (25 V and 50 V)
- introducing the distance between the electrodes for the resistivity in metres (m) and feet (ft),
- memory of 990 measurements (10 banks of 99 cells each),
- calibration of clamp used,
- real time clock (RTC),
- data transmission to the computer (USB),
- indication of battery state.
Electric security:
- type of insulation: double, according to EN 61010 – 1 and IEC 61557
- measurement category: CAT IV 300 V acc. to EN 61010 – 1
- protection class acc. to EN 60529: IP54
Rated operational conditions:
- operation temperature: -10…+50°C
- storage temperature: -20…+70°C
- humidity: 20…80%
Other technical data:
- LCD display: graphic, backlighted
- interface: USB
- number of measurements carried out of set of batteries: > 1200
- warranty: 24 months
Measurement of interference voltage
| Range | Resolution | Accuracy |
| 0…100 V | 1 V | ±(2% m.v. + 3 digits) |
Measurement of interference frequency
| Range | Resolution | Accuracy |
| 15…450 Hz | 1 Hz | ±(1% m.v. + 2 digits) |
Measurement of earthing resistance (method 3- and 4-pole)
measurement range to IEC61557 – 5: 0,100 Ω…19,9 kΩ
| Range | Resolution | Accuracy |
| 0,000…3,999 Ω | 0,001 Ω | ±(2% m.v. + 4 digits) |
| 4,00…39,99 Ω | 0,01 Ω | ±(2% m.v. + 2 digits) |
| 40,0…399,9 Ω | 0,1 Ω | |
| 400…3999 Ω | 0,001 kΩ | |
| 4,00k…19,99 kΩ | 0,01 kΩ | ±(5% m.v. + 2 digits) |
Measurement of continuity of equipotential bondings and protective conductors (Rcont)
measurement range to IEC61557 – 4: 0,045 Ω…19,99 kΩ
| Range | Resolution | Accuracy |
| 0,000…3,999 Ω | 0,001 Ω | ±(2% m.v. + 4 digits) |
| 4,00…39,99 Ω | 0,01 Ω | ±(2% m.v. + 2 digits) |
| 40,0…399,9 Ω |
0,1 Ω |
|
| 400…3999 Ω | 0,001 kΩ | |
| 4,00k…19,99 kΩ | 0,01 kΩ | ±(5% m.v. + 2 digits) |
Measurement of resistance of auxiliary electrodes RH and RS
| Range | Range | Accuracy |
| 0…999 Ω | 1 Ω | ±(5% (RS+RE+RH) + 8 digits) |
| 1,00k…9,99 kΩ | 0,01 kΩ | |
| 10,0k…19,9 kΩ | 0,1 kΩ |
Measurement of multiple earthing resistance with using the clamp and auxiliary
electrodes (3p + clamp)
| Range | Resolution | Accuracy |
| 0,000…3,999 Ω* | 0,01 Ω | ±(8% m.v. + 4 digits) |
| 10,0…99,9 Ω | 0,01 Ω | ±(8% m.v. + 3 digits) |
| 100…999 Ω | 0,1 Ω | |
| 1,00k…1,99 kΩ | 1 Ω |
* – in range 0,000…0,045 Ω the accuracy is not specified.
Measurement of multiple earthing resistance with using double clamps
| Range | Resolution | Accuracy |
| 0,00…19,99 Ω | 0,1 Ω | ±(10% m.v. + 3 digits) |
| 20,0…149,9 Ω | 0,1 Ω | ±(20% m.v. + 3 digits) |
Measurement of ground resistivity Measurement method: Wennera, ρ=2πLRE
| Range | Resolution | Accuracy |
| 0,0…199,9 Ωm | 0,1 Ωm | depending on measurement accuracy RE with 4p method, but not less than ±1 digit |
| 200…1999 Ωm | 1 Ωm | |
| 2,00k…19,99 kΩm | 0,01 kΩm | |
| 20,0k…99,9 kΩm | 0,1 kΩm | |
| 100k…999 kΩm | 1 kΩm |
L – distance between probes: 1…50 m
Measurement of AC current (leakage)
| Range | Resolution | Accuracy |
| 0,1…99,9 mA 1 | 0,1 mA | ±(8% m.v. + 5 digits) |
| 100…999 mA 1 | 1 mA | ±(8% m.v. + 3 digits) |
| 1,00…4,99 A 1,2 | 0,01 A | ±(5% m.v. + 5 digits)1 unspecified 2 |
| 5,00…9,99 A 1,2 | 0,01 A | ±(5% m.v. + 5 digits) |
| 10,0…99,9 A 1,2 | 0,1 A | |
| 100…300 A 1,2 | 1 A |
1 – receiving clamp (diameter 52 mm) – C-3
2 – flexible clamp (Rogowsky coil) with diameter 400 mm – F-1
Measurement of dynamic earthing resistance (RD) with impulse wave method (4p )
| Range | Resolution | Accuracy |
| 0,0…99,9 Ω | 0,1 Ω | ±(2,5% m.v. + 3 digits) |
| 100…300 Ω | 1 Ω |
choice impulse edges: 4/10μs, 8/20μs, 10/350μs
„m.v.”- measured value
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