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Sonel MRU-12 User Manual
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Sonel MRU-12 User Manual

Earth resistance meter
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Summary of Contents for Sonel MRU-12

  • Page 3 USER MANUAL EARTH RESISTANCE METER MRU-12 SONEL S.A. Wokulskiego 11 58-100 Świdnica Poland Version 1.00 31.10.2024...
  • Page 4 The MRU-12 meter is a modern, easy and safe measuring device. Please acquaint yourself with this manual in order to avoid measuring errors and prevent possible problems in operation of the meter. MRU-12 – USER MANUAL...

  • Page 5: Table Of Contents

    4P, ρ ........................... 37 9.3.2 Influence of the auxiliary electrodes on earth resistance measurements for function 4P, ρ ......................... 37 3P, R 9.3.3 Additional uncertainties according to IEC 61557-5 (R 3P) ............ 37 10 Manufacturer ....................38 MRU-12 – USER MANUAL...
  • Page 6 MRU-12 – USER MANUAL...

  • Page 7: General Information

    • CAT III – concerns measurements performed in buildings installa- tions, • CAT IV – concerns measure- ments performed at the source of low voltage installation. MRU-12 – USER MANUAL...

  • Page 8: Safety

    • MRU-12 meter is designed to measure earth resistance and soil resistivity values. Any application that differs from those specified in the present manual may result in a damage to the device and constitute a source of danger for the user.

  • Page 9: Quick Start

    The result of the last measurement is remembered until the next measurement is activated or the measurement parameters are changed. Use the ESC button to go to the starting screen of a given function and press ENTER to display the last measurement result. MRU-12 – USER MANUAL...
  • Page 10 ◄ ◄ ◄ ▪ - - - ▲ ▪ 50 Hz ▪ m ▪ on ▪ 300 s ▪ on ▼ ▪ 60 Hz ▪ ft ▪ off ▪ 600 s ▪ off ▪ 900 s MRU-12 – USER MANUAL...
  • Page 11 ► ► ► ► SUPP UPDT FACT conf ◄ ◄ ◄ ◄ ▪ ACCU ▪ yes ▪ BATT ▪ no ▲ ◄ ◄ ◄ … … … … ▼ ► ► ► MRU-12 – USER MANUAL...

  • Page 12: Measurements

    24 V but lower than 40 V, the xxV!, >24V, NOISE! and measurement is blocked. The interference voltage is lower than 24 V, but with a high NOISE! value - the measurement result may be affected by addi- tional uncertainty. MRU-12 – USER MANUAL...

  • Page 13: Measurement Of Earth Resistances With 3-Pole Method (R 3P)

    → meter → H current electrode → earth → tested earth electrode; • S electrode (voltage electrode) for measuring the voltage drop across the resistance of the meas- ured earthing as a result of current flow. Disconnect the tested earth electrode from the installation of the facility. MRU-12 – USER MANUAL...
  • Page 14 The earth electrode being tested should be connected to E socket of the meter with the lead. • The earth electrode being tested and the current electrode and the voltage electrode should be located in one line. MRU-12 – USER MANUAL...
  • Page 15 24 V. Voltage of interferences is measured up to the level of 100 V, but above 40 V it is signalled as dangerous. The meter must not be connected to voltages exceeding 100 V. MRU-12 – USER MANUAL...
  • Page 16 Flashing edges of symbols: E or H or S, two or all three at Flashing edges the same time: disconnected one, two or three leads to the terminals, or the resistance of the auxiliary auxiliary elec- trode/s is outside the measuring range. MRU-12 – USER MANUAL...

  • Page 17: Measurement Of Earth Resistances With 4-Lead Method (R 4P)

    The meter is in the mode of measuring the in- terference voltage between the test terminals. Set the parameters according to the following algorithm and the rules for setting the general parameters. ▲ ▪ 25 V ▼ ▪ 50 V MRU-12 – USER MANUAL...
  • Page 18 R whereas the upper part of the screen shows additional results for R . The re- sult is displayed for 20 seconds. The result can be recalled by pressing ENTER button. MRU-12 – USER MANUAL...
  • Page 19 In majority of cases the achieved measurement accuracy is satisfactory. However, you should always be aware of the uncertainty included in the measurement. MRU-12 – USER MANUAL...
  • Page 20 Ω value Flashing symbols: Flashing symbols E or H or S, or both of them, or all three at the same time, one or two or three test leads are dis- connected from the measurement sockets. MRU-12 – USER MANUAL...

  • Page 21: Measurement Of Earth Resistances With 2-Pole Method (R 2P)

    Set the parameters according to the following algorithm and the rules for setting the general parameters. ▲ ▪ 25 V ▼ ▪ 50 V Test leads should be connected to the measurement terminals in the device, as shown above. MRU-12 – USER MANUAL...
  • Page 22 24 V but lower than 40 V, the NOISE! and measurement is blocked. The interfering signal (noise signal) is below 24 V, but with NOISE! a high value - the measurement result may be affected by additional uncertainty. MRU-12 – USER MANUAL...

  • Page 23: Soil Resistivity Measurement (Ρ)

    S socket of the meter. • Connect the voltage elec- trode driven into ground to the ES socket of the meter. • Connect the current elec- trode driven into ground to the E socket of the meter. MRU-12 – USER MANUAL...

  • Page 24: Schlumberger Method

    E socket of the meter. 3.5.3 Measurements Connect the measuring system according to sec. 3.5.1 or sec. 3.5.2. Turn on the meter using ON/OFF button. Using ◄► buttons go to ρ function. MRU-12 – USER MANUAL...
  • Page 25 Earth resistivity measurement may be performed if the interference voltage does not exceed 24 V. The interference voltage is measured up to 100 V, but over 40 V is it signaled as hazardous. Do not connect the meter to a voltage exceeding 100 V. MRU-12 – USER MANUAL...
  • Page 26 Flashing symbols E or ES or H or S, or two of them, or Flashing symbols: three, or all of them at the same time – one or two or three or four test leads are disconnected from the measurement sockets. MRU-12 – USER MANUAL...

  • Page 27: Memory Of Measurement Results

    After the measurement, press ENTER. The meter is in the memory enter mode. Select the bank and cell number acc. To section 4.2 or leave the current ones. Cell is empty. Cell includes a result. Confirm by pressing ENTER. MRU-12 – USER MANUAL...
  • Page 28 Then, the meter again displays the last measurement result. The saved data include a complete set of results (main and additional) for a given measurement function plus the set measurement parameters. MRU-12 – USER MANUAL...

  • Page 29: Changing The Cell And Bank Number

    The cell number is flashing. The bank and cell number which you wish to browse is changed with the SET/SEL button and then with the ▲▼ arrows. If the cell/ bank number is flashing, it can be changed. MRU-12 – USER MANUAL...

  • Page 30: Clearing The Memory

    Press ENTER to start deleting or ESC to abort. The deletion progress is shown on the screen as scrolling cell numbers. When deletion is completed, the me- ter generates three short audio sig- nals and sets the cell number to 1. MRU-12 – USER MANUAL...

  • Page 31: Clearing The Whole Memory

    ESC to abort. The deletion progress is shown on the screen as scrolling bank and cell numbers. When deletion is complet- ed, the meter generates three short audio signals and sets the cell num- ber to 1. MRU-12 – USER MANUAL...

  • Page 32: Communication With Computer

    In order to ensure the communication of the meter with a computer, additional Bluetooth module and software is required. A program that may be used for this purpose is Sonel Reader. It allows us- ers to read and display the measurement data stored in the meter memory. This program may be downloaded free from the manufacturer's website.

  • Page 33: Power Supply

    Message bAtt indicates that batter- ies/rechargeable batter- ies are totally discharged, all measurements are blocked. The meter switches off automatically after 5 sec. MRU-12 – USER MANUAL...

  • Page 34: Replacing (Rechargeable) Batteries

    Replacing (rechargeable) batteries MRU-12 is powered by four AA alkaline LR6 batteries or rechargeable batteries of NiMH type. The (rechargeable) batteries are placed in the compartment at the bottom of the enclosure. The de- vice is not equipped with an internal battery charger. Rechargeable batteries must be recharged in an external charger.

  • Page 35: General Principles Regarding Using Ni-Mh Rechargeable Batteries

    If meter is to be stored for a prolonged period of time, the batteries must be removed from the device. • In order to prevent a total discharge of the battery pack in the case of a prolonged storage, charge it from time to time. MRU-12 – USER MANUAL...

  • Page 36: Dismantling And Disposal

    • Measuring current at the short circuit of > 20 mA. • Measuring frequency of 125 Hz or 150 Hz. • Selected test voltage: 25 V or 50 V. • Maximum interference voltage for the R measurement is 24 V. MRU-12 – USER MANUAL...
  • Page 37 (A): 3….50 m or 3…150 ft Measurement of resistance of auxiliary electrodes R and R Range Resolution Accuracy 0…999 Ω 1 Ω 1.00…9.99 kΩ 0.01 kΩ ±(5% + 8 digits) 10.0…19.9 kΩ 0.1 kΩ MRU-12 – USER MANUAL...

  • Page 38: Operating Data

    CAT III 150 V to ground (max 150 V between inputs) or CAT IV 100 V to ground (max 100 V between inputs). Markings and symbols indicated on the instrument are to be considered valid when using it at altitude lower than 2000 m. MRU-12 – USER MANUAL...

  • Page 39: Additional Data

    ±0.2 digit/°C for R<1 kΩ Temperature ±0.07%/°C ±0.2 digit/°C for R≥1 kΩ According to the formulas shown Serial interference voltage in par. 9.2.1 (U =3V 50/60Hz) Resistance earth contact According to the formula in probes par. 9.3.2 MRU-12 – USER MANUAL...

  • Page 40: Manufacturer

    The manufacturer of the device and provider of guarantee and post-guarantee service: SONEL S.A. Wokulskiego 11 58-100 Świdnica Poland tel. +48 74 884 10 53 (Customer Service) e-mail: customerservice@sonel.com web page: www.sonel.com NOTE! Service repairs must be performed only by the manufacturer. MRU-12 – USER MANUAL...
  • Page 41 NOTES MRU-12 – USER MANUAL...
  • Page 42 NOTES MRU-12 – USER MANUAL...