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Summary of Contents for Sonel MRU-21
- Page 2 MRU-21 – USER MANUAL...
- Page 3 USER MANUAL EARTH RESISTANCE METER MRU-21 SONEL S.A. Wokulskiego 11 58-100 Świdnica Poland Version 1.06 23.07.2021...
- Page 4 The MRU-21 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 operation of the meter. MRU-21 – USER MANUAL...
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Page 5: Table Of Contents
9.2 Additional information .................... 28 9.2.1 measurement ......................28 9.2.2 measurement ..................... 29 CONT 10 Accessories ....................30 10.1 Standard accessories .................... 30 10.2 Optional accessories ....................30 11 Manufacturer ....................31 12 Laboratory services ..................32 MRU-21 – USER MANUAL... -
Page 6: Safety
MRU-21 meter is designed to measure earth resistance and the resistance of protective conductors and equipotential bondings. 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 7: Settings
Un = 25 V or 50 V, SuPP = bAt (disposable batteries) or Acc (rechargeable batteries). Press ENTER to validate the changes and exit the mode, or..press ESC to exit the setting mode without validating the changes. MRU-21 – USER MANUAL... -
Page 8: Measurements
The voltage electrode (driven into earth) should be connected to S socket of the meter. The tested earth electrode should be connected to E socket of the meter. The tested earth electrode and the current electrode and the voltage electrode should be aligned. MRU-21 – USER MANUAL... - Page 9 Resistance of earth electrode R Read the auxiliary results (sequence as below) by pressing << and >>. Resistance of current electrode Resistance of voltage electrode Additional uncertainty caused by resistance of the auxiliary electrodes. MRU-21 – USER MANUAL...
- Page 10 In majority of cases the measurement accuracy achieved is satisfactory. However, one should always be aware of the uncertainty included in the measurement. - Factory calibration includes the resistance of the 2.2 m test lead (supplied). MRU-21 – USER MANUAL...
- Page 11 Measured voltages or currents are too low in relation to the long audio signal noise, or highly unstable measurement result. (The symbol is displayed instead of the result). Maximum allowed temperature inside the meter is exceeded. MRU-21 – USER MANUAL...
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Page 12: Earth Resistance Measurement With 2-Pole Method (R 3.3 Measurement Of Resistance Of Earth Connection And Equipotential Bonding (Rcont )
Read the interference voltage on the auxiliary display. Press START. Perform the measurement. Interference voltage. Read the measurement result. Measured resistance. Note: - Factory calibration includes the resistance of the 1.2 m and 2.2 m test leads (supplied). MRU-21 – USER MANUAL... - Page 13 Measured voltages or currents are too low in relation to the long audio signal noise, or highly unstable measurement result. (The symbol is displayed instead of the result). Maximum allowed temperature inside the meter is exceeded. MRU-21 – USER MANUAL...
- Page 14 Turn on the meter. Turn the rotary switch to the R position. CONT Connect the tested facility to the S and E terminals. 1,2m 2,2m The meter is ready for measurement. Press START. Perform the measurement. MRU-21 – USER MANUAL...
- Page 15 CONT 1…3 V RMS interference voltage during CONT measurement. Measurement is slightly unstable. The results may include an additional uncertainty. long audio signal Measurement is highly unstable. Maximum allowed temperature inside the meter is exceeded. MRU-21 – USER MANUAL...
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Page 16: Calibration Of Test Leads
Press START. Perform autozeroing. Autozeroing completed. Note: - Remember that the resistance of crocodile clips and crocodile-banana connections is added to the resistance of the test leads. MRU-21 – USER MANUAL... -
Page 17: Turning Autozero Off
1.2 m and 2.2 m leads. NOTE It suffices when the compensation for given test leads is performed only once. It is remembered when the meter is turned off. MRU-21 – USER MANUAL... -
Page 18: Memory
Memory The MRU-21 meters feature memory that can store 990 single measurement results The whole memory is divided into 10 memory banks, with 99 cells in each bank. Each measurement result can be stored in a memory cell marked with a selected number and in a selected memory bank. Thanks to this, the user of the meter can, at his/her option, assign memory cell numbers to individual measurement points and the memory bank numbers to individual facilities. - Page 19 Press ENTER to overwrite the result or ESC to abort. Note: - Stored in the memory is a complete set of results (main result and supplementary results), as well as the test voltage for R MRU-21 – USER MANUAL...
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Page 20: Viewing Memory Data
Turn the rotary switch to the MEM position. The content of the last saved cell appears. Use the symbols to select the bank... or use the symbols to select the cell. Press << or >> to view additional results. MRU-21 – USER MANUAL... -
Page 21: Deleting Memory Data
Set the bank number to be deleted. Set the cell number before “1”..the cell number disappears, and appears the symbol indicating the readiness to delete. Press ENTER . The “?” and symbols appear, asking you to confirm deletion. MRU-21 – USER MANUAL... -
Page 22: Deleting The Whole Memory
4.3.2 Deleting the whole memory Turn on the meter. Turn the rotary switch to the MEM position. Set the bank number between “0” and “9”..the bank number disappears, and appears the symbol , indicating the readiness to delete. MRU-21 – USER MANUAL... -
Page 23: Communication With A Computer
If the rotary switch is in the MEM position, after detecting the USB connection with a computer the meter automatically goes to the data transmission mode and displays the following screen. To transmit data, follow the instructions of the software. MRU-21 – USER MANUAL... -
Page 24: Meter Power Supply
Consequently, such measurements cannot prove that the tested earthing system is correct. Replacement of batteries The MRU-21 is powered by four R14 disposable or rechargeable batteries (alkaline batteries are recommended). The disposable or rechargeable batteries are placed in the compartment at the bottom of the enclosure. - Page 25 After replacement of batteries, the meter when turned on, starts in the power supply selection mode. Selected power supply: rechargeable batteries: Use the symbols to select the power supply: bAt (disposable batteries) or Acc (rechargeable batteries). MRU-21 – USER MANUAL...
- Page 26 (the discharge characteristics of disposable and rechargeable batteries are different). NOTE! Have the meter serviced in case of battery leakage inside the compartment. Batteries must be recharged in an external charger. MRU-21 – USER MANUAL...
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Page 27: Cleaning And Maintenance
Worn-out electronic equipment should be sent to a collection point in accordance with regulations related to Waste Electrical and Electronic Equipment. Before the equipment is sent to a collection point, do not attempt to dismantle any elements. Observe the local regulations concerning disposal of packages, worn-out batteries and accumulators. MRU-21 – USER MANUAL... -
Page 28: Technical Specifications
=300 1,0000 =100 0,1000 ądowej Rezystancj elektrody Current electrode resistance Rezystancj uziemienia Earth resistance 0,0100 =0,3 0,0010 1000 10000 100000 Rezystancja elektrody napięciowej Rs[] Voltage electrode resistance Rs[] Auxiliary electrodes resistance and measurement accuracy MRU-21 – USER MANUAL... - Page 29 AUTO-OFF ......................5 minutes x) altitude a.s.l........................≤2000 m* y) the product meets the EMC requirements acc. to ......EN 61326-1 and EN 61326-2-2 z) quality standard ......development, design and manufacturing are ISO 9001 compliant MRU-21 – USER MANUAL...
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Page 30: Additional Information
+ 0.05)U 25 V, 50 V 100 …1.99 k (0.001R 0.001U + 0.5)U 9.2.1.3 Additional uncertainty caused by ambient temperature ± 0.25 digit/°C for Uwy = 50 V, ± 0.33 digit/°C for Uwy = 25 V MRU-21 – USER MANUAL... -
Page 31: Cont Measurement
Reference conditions or Designatio Additional influencing factors operating range uncertainty Reference position Position ±90° ÷ U Power supply voltage 0 ÷ 35°C ±0.15%/°C Storage temperature Working uncertainty where A = accuracy MRU-21 – USER MANUAL... -
Page 32: Accessories
WAPRZ025BUBBSZ WAPRZ050YEBBSZ 25 m test lead (blue) 50 m test lead WASONG80 WAFUTL3 Auxiliary electrode, 80 cm case L-3 (for auxiliary electrodes 80 cm) WAZACIMA1 Vise MRU-21 – USER MANUAL... -
Page 33: Manufacturer
The manufacturer of the device and provider of warranty and post-warranty service: SONEL S.A. Wokulskiego 11 58-100 Świdnica Poland tel. +48 74 858 38 60 fax +48 74 858 38 09 E-mail: export@sonel.pl Web page: www.sonel.pl NOTE Service repairs must be performed solely by the manufacturer. MRU-21 – USER MANUAL... -
Page 34: Laboratory Services
National Metrological Institute. According to ILAC-G24 „Guidelines for determination of calibration intervals of measuring instruments”, SONEL S.A. recommends periodical metrological inspection of the instruments it manufactures no less frequently than once every 12 months. - Page 36 MRU-21 – USER MANUAL...
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