Sonel WMGBMRU120 User Manual
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Sonel WMGBMRU120 User Manual

Earth resistance meter
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Summary of Contents for Sonel WMGBMRU120

  • Page 2 MRU-120 – USER MANUAL...
  • Page 3 USER MANUAL EARTH RESISTANCE METER MRU-120 SONEL S. A. Wokulskiego 11 58-100 Świdnica Version 2.10 28.03.2022...
  • Page 4 The MRU-120 meter is a modern, easy and safe measuring device. Please acquaint yourself with the present manual in order to avoid measuring errors and prevent possible problems related to opera- tion of the meter. MRU-120 – USER MANUAL...

  • Page 5: Table Of Contents

    TABLE OF CONTENTS 1 Safety ........................ 5 2 Menu ........................6 2.1 Measurement settings ....................6 2.1.1 Mains frequency ........................... 7 2.1.2 Calibration of the measurement clamp C-3 ................. 7 2.1.3 Earth resistivity settings ........................ 9 2.2 Meter settings......................9 2.2.1 LCD contrast ..........................
  • Page 6 10 Technical data....................38 10.1 Basic data ....................... 38 10.2 Additional data ......................40 10.2.1 Influence of the serial interference voltage U upon earth resistance measurements for functions R 3P, R 4P, R 3P+C ....................40 10.2.2 Influence of the serial interference voltage U upon earth resistance measurements for function ρ...

  • Page 7: Safety

    Safety The MRU-120 meter has been designed to realise measurements whose results determine the safety conditions of the installation. Therefore, in order to provide conditions for correct operation and the correctness of the obtained results, the following recommendations must be observed: ...

  • Page 8: Menu

    Menu The menu is available at any position of the knob. Press MENU. Using buttons highlight the required position. Press ENTER to select the option. Measurement settings Using buttons highlight the required position. Press ENTER to select the option. MRU-120 – USER MANUAL...

  • Page 9: Mains Frequency

    2.1.1 Mains frequency It is necessary to determine the frequency of the mains which is the source of potential interfer- ence in order to select the appropriate frequency of the measurement signal. Solely measurements based upon the correct frequency of the measurement signal will guarantee the optimum interference filtering.
  • Page 10 Once the calibration has been successfully concluded, The following will be displayed. The meter has determined the correction factor for connected clamp. The factor is saved in the memory also when the power supply of the meter is off until the following successful calibration of the clamp has been performed.

  • Page 11: Earth Resistivity Settings

    2.1.3 Earth resistivity settings Using buttons select the result and the distance unit and press ENTER to confirm. Meter settings Using buttons select required item. Press ENTER to confirm. 2.2.1 LCD contrast Using the buttons set the contrast value and press ENTER. MRU-120 –...

  • Page 12: Auto-Off Settings

    2.2.2 AUTO-OFF settings The setting determines the time before the automatic turning-off of the device when it is not in use. Use buttons to set the time or AUTO-OFF disable, press ENTER. 2.2.3 Display settings The setting permits to turn on/off the setting bar display. Use buttons to set the dis- play of the setting bar (measurement parameters), press ENTER.

  • Page 13: Battery Discharging

    Before you proceed to updating the programme, download from the manufacturer’s web page (www.sonel.pl) the meter programming software, install it in the computer and connect the meter to the computer. Having chosen the Program update in the MENU, proceed in accordance with the instructions displayed by the programme.

  • Page 14: Measurements

    Measurements Note: During measurements the status bar is displayed. Measurement of resistance of earth connection and equipotential bonding (2P) Note: The measurement complies with the requirements specified in the standard EN 61557-4 (U<24 V, I>200 mA for R≤10 Ω). Turn the meter on. Set the rotational function selector at 2P.

  • Page 15: Calibration Of The Test Leads

    Read out the result. The result is displayer for 20 s. It may be displayed again ENTER is pressed. Additional information displayed by the meter R>20,0kΩ Measurement range exceeded. >40V! and a con- The voltage on the measurement points exceeds 40 V, tinuous sonic signal the measurement is blocked.

  • Page 16: Auto-Zeroing Off

    Once the auto-reset function Has concluded the following will be displayed: Auto-zeroing is signalled by the legend AUTOZERO on the right-hand side of the display. 3.2.2 Auto-zeroing off Turn the meter on. Set the rotational function selector at 2P. Press F1. Separate the test leads.

  • Page 17: Earth Resistance Measurement With 3-Pole Method (R 3P)

    Earth resistance measurement with 3-pole method (R The basic kind of the earth resistance measurement is 3-pole measurement. Disconnect the tested earth electrode for the object installation. Turn the meter on. Set the rotational function selector at 3P. Connect the current electrode driver into ground to the H socket of the meter. Connect the voltage electrode driver into ground to the S socket of the meter.
  • Page 18 Press F1 to order to modify the measuring voltage. Use buttons to set the measuring voltage and press ENTER. Press START In order for the test to commence measurement. Read out the result. Current electrode resistance Voltage electrode resistance Additional uncertainty caused by the resistance of the electrodes Displayed, when δ>30% The result is displayer for 20 s.
  • Page 19 Repeat the measurements (see points 3, 7 and 8) moving the voltage electrode by a couple of meters: approaching it to and moving it away from the tested earth electrode. If the R test results differ more than 3%, then it is necessary to increase significantly the distance between the current electrode from the earth electrode in question and repeat the measurement.

  • Page 20: Earth Resistance Measurement With 4-Wire Method (R 4P)

    Earth resistance measurement with 4-wire method (R The 4-wire method is recommended in the case of measurements of earth resistance of very low values. It permits to eliminate the influence of the test leads resistance over the result of the meas- urement.
  • Page 21 The meter is ready for measurement. The auxiliary display shows the value of the interference voltage and its fre- quency. The setting bar shows the mains frequency set in the MENU. Press F1 to order to modify the measuring voltage. Use buttons to set the measuring voltage and press...
  • Page 22 Repeat the measurements (see points 3, 7 and 8) moving the voltage electrode by a couple of meters: approaching it to and moving it away from the tested earth electrode. If the R test results differ more than 3%, then it is neces- sary to increase significantly the distance between the cur- rent electrode from the earth electrode in question and re- peat the measurement.

  • Page 23: Earth Resistance Measurement With 3-Pole Method With Additional Clamp (R E 3P+C)

    Earth resistance measurement with 3-pole method with additional clamp (R 3P+C) Turn the meter on. Set the rotational function selector at 3P . Connect the current electrode driver into ground to the H socket of the meter. Connect the voltage electrode driver into ground to the S socket of the meter. Connect the tested earth electrode to the E socket of the meter.
  • Page 24 Use buttons to set the measuring voltage and press ENTER. Press START in order for the test to commence measurement. Read out the result. Current electrode resistance Voltage electrode resistance Additional uncertainty caused by the resistance of the electrodes. The result is displayer for 20 s. It may be displayed again ENTER is pressed.
  • Page 25 erated if we measure a low value of the earth resistance with electrodes of a weak contact with the ground (such a situation occurs often if the earth electrode is properly made and the upper layer of the ground is dry and characterised by a low conductivity). Then the relation between the electrode resistance and the resistance of the measured earthing is very high, and so is the case of the meas- urement uncertainty which depends on it.

  • Page 26: Earth Resistance Measurement With Two-Clamp Method (2C)

    Earth resistance measurement with two-clamp method (2C) Two-clamp measurements are applied where there is no possibility of using ground-driven elec- trodes. NOTE! The two-clamp method may be used solely in the case of multiple earthing measurements. Turn the meter on. Set the rotational function selector at Connect the transmission clam to sockets H and E, while the measurements clamp...
  • Page 27 Read out the result. The result is displayed for 20 s. It may be displayed again when ENTER is pressed. Note: Measurements may be performed in the presence of interference current not exceeding 3 A RMS and whose frequency complies with the value set in the MENU.

  • Page 28: Earth Resistivity Measurement (Ρ)

    Earth resistivity measurement (ρ) For the purpose of earth resistivity measurements – which are used as a preliminary measure for the project of earthing systems or in geology – there is a separate function, which is selected by means of the rotational function selector: earth resistivity measurements  . The function is metrolog- ically identical as the 4-wire earth resistance measurement , but it includes an additional procedure of storing of the distance between the electrodes.
  • Page 29 Press F1 to change the measurement voltage. Use buttons to set the measuring voltage and press ENTER. Press START to commerce measure- ment. The meter will activate the mode of selection of the distance between probes. Use buttons to set the dis- tance between electrodes and press ENTER In order to commerce meas- urement.
  • Page 30 Note: Earth resistance measurement may be realised if the interference voltage does not exceed 24 V. The interference voltage is measured up to 100 V. Do not con- nect the meter to a voltage exceeding 100 V. - Calculations are based upon the assumption that the distances between the specific measurement electrodes are equal (the Wenner’s method).

  • Page 31: Memory

    Memory The MRU-120 meters are equipped with a memory whose capacity is 990 results of resistance measurements. Individual measurements are saved in memory cells. The whole memory is divided into 10 banks with 99 cells each. Each result may be saved in a cell of a defined number and in the selected bank, so the user of the meter may, at their own discretion assign numbers of the cells to individual measurement points and the numbers of the banks to individual objects, realize measure- ments in any order and repeat them without loosing other data.

  • Page 32: Memory Erasing

    Memory erasing Note: - During the process of memory erasing the progress bar is being displayed. Turn the meter on. Set the rotational function selector at MEM. Using the buttons highlight “Memory erasing”. Press ENTER. MRU-120 – USER MANUAL...

  • Page 33: Memory Browsing

    Use the buttons to select complete "Memory erase", "Bank erase" or "Measurement erase" Follow the displayed instructions. Memory browsing Use the buttons to highlight “Memory browsing”. Press ENTER. Use the buttons to select bank and the buttons to select a cell. Note: - During a memory search empty cells and banks are unavailable.

  • Page 34: Data Transmission

    USB cable and appropriate software. If the required accessories such have not been purchased along with the meter, then they are available from the manufacturer or an authorised distributor. The accessories may be used in case of many devices manufactured by SONEL S.A. which are equipped with the USB interface.

  • Page 35: Replacement Of Accumulators

    Note:  The displayed BAT symbol means insufficient power supply voltage and the need to charge the accumulators,  Measurements realized with an insufficient meter power supply voltage are distorted with addi- tional errors which are impossible to ascertain by the user and thus they cannot constitute a basis for a conclusion of correctness of the tested earthing system.

  • Page 36: Fuse Replacement

    Fuse replacement Remove the battery compartment to get access to two replaceable fuses: - FST 1 A 250 VAC, 5x20 mm and - 2 A 250 VAC, time-delay fuse, 5x20 mm. If the instrument or battery charger does not work, before sending it for servicing, check the fuses and, if they are blown, replace them with identical ones.

  • Page 37: Discharging Of Accumulators

    Additional information displayed by the meter Message Cause Proceeding Excessive voltage at the Check the contacts of the accumulator Battery connection error! accumulator package dur- package. Should the problem persist, ing charging. replace the package. No communication with the Check the contacts of the accumulator accumulator controller or package.

  • Page 38: General Principles Regarding Using Ni-Mh Accumulators

    Use buttons to select Battery discharging, and press ENTER. Read the displayed text and accept. Discharging, which may last up to 10 hours depending on the level of the charge of the package, is signalled with the following message: Discharging of accumulators in progress. General principles regarding using Ni-MH accumulators - If you do not use the device for a prolonged period of time, then it is recommended to remove the accumulators and store them separately.

  • Page 39: Cleaning And Maintenance

    Cleaning and maintenance NOTE! Apply solely the maintenance methods specified by the manufacturer within the present manual. The casing of the meter may be cleaned with a soft, damp cloth using all-purpose detergents. Do not use any solvents or cleaning agents which might scratch the casing (powders, pastes, etc.). Clean the auxiliary electrode with water and dry it.

  • Page 40: Technical Data

    10 Technical data  The abbreviation „m.v.” in the accuracy definition means the measured value. 10.1 Basic data Interference voltage measurement U (RMS) Range Resolution Accuracy ±(2% m.v. + 3 digits) 0...100 V  measurement for f 45…65 Hz  frequency of measurements –...
  • Page 41 ................≤0.5 mA m) power supply of the meter ......accumulator package type SONEL NiMH 4.8 V 3 Ah n) parameters of AC adapter for the battery charge ......100 V…240 V, 50 Hz…60 Hz o) number of measurements for 2P ..........

  • Page 42: Additional Data

    v) temperature range suitable for initiating battery charging ........+10C to +40C w) temperatures at which loading is interrupted ....below +5 C and above (or equal to) +50C x) reference temperature ....................... 23 ±2C y) storage temperature..................... -20…+80C z) relative humidity ....................... 20…90% aa) relative humidity nominal ....................

  • Page 43: Influence Of The Auxiliary Electrodes Upon Earth Resistance Measurements For Function Ρ

    10.2.4 Influence of the auxiliary electrodes upon earth resistance meas- urements for function ρ Uncertainty [%]      30000          [Ω], R [Ω] and R [Ω] are values which are displayed by the device. 10.2.5 Influence of the interference current I upon the result of the earth resistance measurement for method R...

  • Page 44: Additional Uncertainties In Accordance With Iec 61557-4 (2P)

    10.2.8 Additional uncertainties in accordance with IEC 61557-4 (2P) Influencing factor Symbol Additional uncertainty Location Power supply voltage 0% (BAT not displayed) ±0,2digit/°C for R<1 kΩ Temperature ±0,07%/°C ±0,2 digit/°C for R≥1 kΩ 10.2.9 Additional uncertainties in accordance with IEC 61557-5 (R 4P, R 3P+C) Influencing factor...

  • Page 45: Optional Accessories

    11.2 Optional accessories Furthermore, the manufacturer and authorized distributors offer the following elements which are not included in the basic accessories package: WASONG80V2 WACEGN1BB   Auxiliary electrode, 80 cm Transmission clamp N-1 WACEGC3OKR WAPRZLAD12SAM  Reception clamp C-3  Cable to charge the accumulators from the car lighter socket WAFUTL3...

  • Page 46: Positions Of The Meter's Cover

    3 – Cover in the position that enables convenient use of the meter suspended on the neck by means of hanging straps. 13 Manufacturer The manufacturer of the device, which also provides guarantee and post-guarantee service is the following company: SONEL S.A. Wokulskiego 11 58-100 Świdnica Poland tel. +48 74 858 38 60...

  • Page 47: Laboratory Services

    National Metrological Institute. According to ILAC-G24 „Guidelines for determination of calibration intervals of measuring instru- ments”, SONEL S.A. recommends periodical metrological inspection of the instruments it manufac- tures no less frequently than once every 12 months.
  • Page 48 NOTES MRU-120 – USER MANUAL...
  • Page 49 NOTES MRU-120 – USER MANUAL...
  • Page 50 NOTES MRU-120 – USER MANUAL...
  • Page 52 MRU-120 – USER MANUAL...

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