Sonel – MRU-120 Earth Resistance Meter

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Datasheet - MRU-120


The Sonel MRU-120 Ground Resistance Tester allows the user to take earth resistance methods, using the 3-pole and 4-pole methods. Additionally, the MRU-120 offers selective earth resistance measurements, using an auxiliary clamp, meaning no influences from parallel earths or opening of junctions is required..

It is possible to employ the Wenner method of measurement, the electrode and clamp method, for multiple earthing, or the two clamp method for measurements without the use of auxiliary rods. Additionally the MRU-120 will automatically calculate the resistance of electrodes and compensate for this reading for greater accuracy. Interference voltages and frequencies are measured with the MRU-120 to eliminate inaccuracies caused by these phenomena. The MRU-120 will calculate the distance between electrodes in metres or feet. When utilising a clamp for measurements, the MRU-200 can calibrate the used clamp. This instrument is built for accuracy and speed for professional measurements of various applications where ground resistance is required.

The MRU-120 is a professional grade instrument with all functions being selectable on its rotary dial. Being a menu driven instrument, all functions are clearly displayed on its large multifunction backlit graphical LCD display, with functions selected via the soft touch keys. Its’ ergonomic design permits the user to hang the meter for hands free use.

The Sonel MRU-120 is supplied as a testing kit in a professional quality carry bag, complete with test leads and banana plugs, 25m test reel (red), 25m test reel (blue) shielded test, reel on lead (50m), auxiliary earth contact rod, battery pack and charger, hanging straps, USB cable and calibration certificate.

  • Multifunction Earth Test Set
  • Measurement of earth resistance (3-pole and 4-pole method)
  • Measurement of multiple earthing resistance (3-lead + clamp)
  • Measurement of multiple earthing resistance with use of 2 clamps
  • Earth resistivity measurement
  • It allows to take the measurements of:
    • earth resistance using auxiliary electrodes,
    • earth resistance using auxiliary electrodes and clamp (for measurements of multiple earth)
    • earth resistance using double clamps (for measurement of earthing when it is impossible to use auxiliary electrodes),
    • ground resistivity (Wenner method),
    • 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.


    • 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 50 Hz, 60 Hz
    • selection of maximum measuring voltage (25 V and 50 V)
    • introducing the distance between the electrodes for the resistivity in metres (m),
    • memory of 990 measurements (10 banks of 99 cells each),
    • calibration of clamp used,
    • real time clock (RTC),
    • data transmission to the computer (USB, wireless),
    • indication of battery state.
  • Includes: 4x 30cm earth stakes, 1.2m red test lead, 2.2m black test lead, 2x 25m test lead reels red & blue, 50m yellow test lead reel, red pin probe, black crocodile clip, carry case, USB cable, power supply adaptor, NiMH rechargeable battery, battery charger cable, hanging straps, Sonel Reader software, calibration certifcate & manual, 2 years warranty.