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.

Sonel MRU-200 XL3C3N1 comes with XL-3 hard carrying case, C-3 receiving clamp and N-1 transmitting clamp.

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.