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1. 22 220020020000000000000000000000 16 MONITORING OF THE POWER SUPPLY VOLTAGE ecce eene 16 REPLACEMENT OF BATTERIES RECHARGEABLE BATTERIES 16 GENERAL PRINCIPLES REGARDING USING NI MH RECHARGEABLE BATTERIES e Dan eet epe e shes 18 CLEANING AND MAINTENANCE 22222000000000000000000000000000000000000 20 DE T Gi Gila Ci 20 DISMANTLING AND UTILIZATION 2 200 20020000000000000000000000 20 TECHNICAL DADA zo ZAB ZORG disc 21 2 SUPPLEMENTARY a 23 91182 111 227 O 23 Meas remeni OF IN CONT 24 FOUIPMEN Saona AREA A 24 STANDARD BOUIPMPBN T 24 OPTIONAL EQUIPMENT e ER LOS 24 MANUFACTURER 26 OPERATING MANUAL MRU 20 version 3 0 OPERATING MANUAL MRU 20 version 3 0 1 Safety MRU 20 meter is designed for measuring parameters important for safety of electrical installa tions Therefore in order to provide conditions for correct operation and the correctness of the obta ined results the following recommendations must be observed Before you proceed to operate the meter acquaint yourself thoroughly with this manual and ob serve the safety regu2. uncertainty Reference conditions or a Additional 510 oarameter range of use MN Reference a voltage EL HEN according to the formula Temperature 35 C detinedin 7 2 2 1 Operational uncertainty B A LISJ E E E where A basic uncertainty 8 Equipment 8 1 Standard Equipment Standard set of equipment supplied by the manufacturer includes e MRU 20 meter WMPLMRU20 e AA batteries 8 pcs e set of test leads lead 30m red on a reel ended with banana plugs WAPRZOSOREBBSZ lead 15m on a reel ended with banana plugs WAPRZ015BUBBSZ lead 2 2m black ended with banana plugs WAPRZ2X2BLBB lead 1 2m blue ended with banana plugs WAPRZ1X2REBB crocodile clip blue KO2 WAKROBU20K02 crocodile clip black KO1 WAKROBL20K01 earth contact test probe rod 30cm 2 pcs WASONG30 carrying case for the meter and its equipment WAFUTL4 harness for the meter WAPOZSZE2 operating manual calibration certificate 8 2 Optional Equipment Additionally the following items not included in the scope of standard equipment may be purcha sed from the manufacturer or the distributors 24 OPERATING MANUAL MRU 20 version 3 0 WAPRZ025BUBBSZ WAFUTL3 e Test lead 25m blue WAPRZ050YEBBSZ e Test lead 50m WAPOZSZP1 e reel for winding test leads WASONG80 e earth contact test probe rod 80 cm probe protective cover 80cm WAZ
3. OPERATION MANUAL EARTH RESISTANCE METER MRU 20 Earth resistance meter MRU 20 is designed to measure earth resistance and the resistance of protective conductors and equi potential bonding The most important features of the MRU 20 include P d earth resistance measure ment in double and three lead arrangement A double lead earth resistance measurement 22 testing the interference vol tage AC and DC with the resistance measurement lock function in case of exce ssive interference rd testing the electrode resis tance to ensure proper accu racy ofthe measurement Z resistance measurement of protective conductors and equipotential bonding compensation of test leads resistance autozeroing 27 large and clear LCD display ZE ergonomic operation 22 power supply disposable or rechargeable batteries 27 battery charge level indica tion AUTO OFF function f hermetic enclosure Z robust and ergonomic mea surement accessories along with a case to carry them Ajyinunuoo 199 ynunuoo N yy Jndul uswaunseaw 7y 6 uuee jusuejnsea 3 JeEuiuJe jndul opoJjoe e juauno H 3015 IWNIWYAL IWO l3 M3IA MRU 20 Measurement voltage changing 25V or
4. Obtained test results may be burdened with additional uncertainty 5 and 4 and long audio signal Very unstable measurement result o 2 4 Calibration of test leads In order to eliminate the impact of the resistance of test leads on measurement result the com pensation autozeroing of resistance may be performed Therefore measurement function has its sub function called AUTOZERO 2 4 1 Activation of Autozeroing W 4 2 Turn meter Set rotational function se lector at Rconr ZERO posi tion REP MO zo p Short the test leads by putting crocodile clips on exposed ends of the test leads Press START button Perform Autozeroing OPERATING MANUAL MRU 20 version 3 0 13 R A NA W Autozeroing Q performed Note remember that the resistance of crocodile clips and crocodile banana connections is added to the resistance of the test leads 2 4 2 Switching off Autozeroing Turn on the meter Set the rotational function se lector at Rconr ZERO posi tion Open out the test leads 4 Press START button Autozeroing was turned off by the user During measurements the meter will compensa R te the resistance of origi zwa pw nal test leads 1 2m and 2 2m 14 OPERATING MANUAL MRU 20 version 3 0 Attention It is sufficient to perform single compensation for the test leads It is stored in m
5. Value of interference voltage is displayed on the auxiliary di splay lt q M 5 Press START button Carry out the measurement Value of interference vol tage Uy n Li R Read out test results w w j Q The value of measured lt gt resistance Note Calibration performed by the manufacturer takes into account the resistance of supplied measure ment leads of 1 2 m and 2 2 m 10 OPERATING MANUAL MRU 20 version 3 0 Additional informations displayed by the meter 30 Interference voltage is too high gt 24V the measure 04 4 ment is impossible and Turn off the source of interferences Uy iu gt y and A Interference voltage is above 50V Immediately disconnect the meter Before re connecting turn off the source of voltage and continuous audio signal o Uy d n Interference voltage is above 100V gt and A Immediately disconnect the meter symbol displayed in stead of voltage value and continuous audio Before re connecting turn off the source of voltage signal o Interruption in measuring circuit gt 1 99kQ RE measuring range is exceeded Interference voltage is above 10V or unstable measure NOISE ment result or measured voltages or currents are low in re lation to noise nm Sand A and Measured voltages or currents are too low in relation to no long audio signal ise or very unstable measurement result Symbol nar 5 is o d
6. tSt CUNS ETE etd pee Dime wb PONE syd vd AGE po R ipae ies A sec Paes 20mA maximum resistance of test electrodes 50kQ RcoNT measuring current with shorted terminals for Ugar gt 9 0 200mA maximum voltage on open terminals for RcoNT e see eee ea eee aaa aaa aaa 13V power supply of the meter alkaline batteries or NIMH rechargeable batteries size AA 8 pcs number of Re measurements gt 1000 50 2 measurements min JIMENSIONS 260 190 60 weight of the meter with batteries approx 1 3 kg elici T RO ad LCD with a backlight WOFKIFIO temperati NE FREE aa dA ERA PRO EEE Za 10 55 C PIO MMMANTE MIDS dil goats tcs toro ot tee ctc kee ee ehe 23 2 C Storage lemperalure ua deda O Aika 20 C 70 C time of automatic switch off 5 electromagnetic compatibility according to EN 61000 6 3 and EN 61000 6 2 quality standard execution design and manufacturing are ISO 9001 compliant OPERATING MANUAL MRU 20 version 3 0 7 2 Supplementary data Data on additional uncertainties are useful mainly when the meter is used in non standard condi tions and for meteorological laboratorie
7. be necessary to format them it is recommended to charge the accumulators from time to time even if not used Modern quick chargers detect both too low and too high temperature of rechargeable batteries and they react to this situation adequately When the temperature is too low charging is prevented as it may irreparably damage rechargeable batteries Increased temperature of rechargeable batteries is a signal to stop charging and it is a typical phenomenon However charging at high ambient temperatu res reduces the lifetime of batteries and causes faster increase of their temperature preventing char ging to the full capacity Remember that in the case of quick charging rechargeable batteries are charged to approximately 80 of their capacity better results may be obtained if the process of charging is continued the charger goes then to the phase of charging with a low current and after next couple of hours the re chargeable batteries are charged to their full capacity Do not charge or use rechargeable batteries in extreme temperatures Extreme temperatures reduce the lifetime of batteries and rechargeable batteries Avoid locating devices powered by rechargeable batteries in very hot places The nominal working temperature must be absolutely observed OPERATING MANUAL MRU 20 version 3 0 19 4 Cleaning and maintenance NOTE Apply only maintenance methods specified by the manufacturerin this manual The casing of the met
8. differ from each other by more than 3 the distance of the current electrode from the earth electrode being tested should be considerably in creased and the measurements should be repeated Note A Measurement of resistance to earth may be carried out if voltage of interferen ces does not exceed 24 V Voltage of interferences is measured up to the level of 100 V but above 50 V it is signaled as dangerous The meter must not be connected to voltages exceeding 100 V Particular attention should be paid to quality of connection between the object being tested and the test lead the contact area must be free from paint rust etc If resistance of test probes is too high Re earth electrode measurement will be burdened with addi tional uncertainty Particularly high uncertainty of measurement occurs when a small value of resi stance to earth is measured with probes that have a weak contact with earth such a situation occurs frequently when the earth electrode is well made and the upper soil layer is dry and slightly conduc tive In such a case the ratio between resistance of the probes and resistance of the earth electrode tested is very high and consequently uncertainty of measurement that depends on this ratio is also very high Then according to guidelines defined in section 7 it is possible to calculate the effect of measurement conditions or to use the attached chart This uncertainty is also displayed in as an additio
9. sec the meter returns to the measure ment mode You can also confirm the choice by pressing the START push button The current electrode driven into earth should be connected to H socket of the meter The voltage electrode driven into earth should be connected to S socket of the meter The earth electrode being tested should be connected to E socket of the meter The earth electrode being tested and the current electrode and the voltage electrode should be located one line OPERATING MANUAL MRU 20 version 3 0 The meter is ready for measurement UJ Value of interference voltage is displayed on the auxiliary di splay a M Ba a Press START button Carry out the measurement Value of interference vol te Uy z R Read out main results NA W i Q earth electrode resistan R lt gt LI Auxiliary results may read after pushing SEL push button SEL RH 1 RH resistance of current m electrode RS wa WW W Rs resistance of voltage al electrode OPERATING MANUAL MRU 20 version 3 0 ER E o Value of additional uncertainty caused by resistance of the electrodes 11 Repeat the measurements points 3 6 shi 5 fting the voltage electrode several meters ii the electrode should be shifted farther and closer to the earth electrode being tested If Re measurement results
10. 50V Turning on and off the meter After turning the meter on the display will show all the numbers and symbols display test The display backlight on off Starting the measurement procedur RZ Displaying all velues related to the last measurement in the following sequence earth resistence Re resistance of auxiliary electrodes R and Rg additional error ROTATIONAL FUNCTION SELECTOR Choosing measurement function 2p measurement of earth resistance using double pole method 3p measurement of earth resistance using three pole method 200mA measurement of the resistance of protective conductors and equipotential bondings ZERO Compensation of test leads resistance used for the measurement of the resistance of protective conductors and equipotential bondings DISPLAY Parameter configuration mode Additional readout field Symbol indicating battery charge level Highlighting the importance of displayed error information signaling the need for using the SET A Operating manual Signaling the presence of Symbol of displayed value interference voltage with R resistance a value enabling the earth resistance measurement with additional resistance of electrode uncertainty resistance of S electrode l additional uncertaity caused AUTO ZERO ZERO by resistance of electrodes 9 4 lee Main disp
11. ACIMA1 cramp LSWPLMRU20 calibration certificate OPERATING MANUAL MRU 20 version 3 0 25 9 Manufacturer The manufacturer of the device which also provides guarantee and post guarantee service is the following company SONEL S A ul Wokulskiego 11 58 100 widnica Poland tel 48 74 858 38 60 fax 48 74 858 38 09 E mail export 2sonel pl Web page www sonel pl Attention Service repairs must be realized only by the manufacturer 26 OPERATING MANUAL MRU 20 version 3 0 WARNINGS AND INFORMATIONS DISPLAYED BY THE METER NOTE The meter is designed to operate at interference voltages below 24V for measurements and below 3V for measurements Voltage values up to 100V are measured but above 50V they are indicated as dangerous The meter must not be connected to voltages exceeding 100V In RE measurement interference voltage gt 24Vrms measurement impossible Turn off the source of interferences or during measurement try to arrange probes differently w In measurement interference voltage gt 50V gt GH and 4 and Immediately disconnect the meter continuous audio signal Before re connecting turn off the source of voltage DFL n 4 In measurement interference voltage gt 100V gt Ol and and Immediately disconnect the meter continuous audio signal Before re connecting turn off the source of voltage In measurement interference voltage is too high gt 3Vrms me
12. asurement 3 and A impossible Turn off the source of voltage R In measurement interference voltage gt 50V gt and Immediately disconnect the meter continuous audio signal Before re connecting turn off the source of voltage with name of an Interruption in measuring circuit or resistance of test probes is higher than 60kQ electrode electrodes and P 9 p g Please check connections in the measuring circuit or reduce the resistance of the measuring probe by its repositioning Er under Cell and mea Uncertainty of R measurement introduced by the resistance of electrodes exceeds surement result and A 30 Reduce the resistance of the probe by its repositioning or increase the dampness of the ground in the direct vicinity of the probe measurement range is exceeded 190 1 measurement range is exceeded gt 50kQ Resistance of test probes is higher than 50kQ but lower than 60kQ Interference voltage for RZ is higher than 100V symbol displayed instead of voltage value Interference voltage with value 1 3Vrms during R 4 measurement Obtained test NOISE results may be burdend with additional uncertainty In measurement interference voltage gt 10V or unstable measurement result or measured voltages or currents are low in relation to noise Measured voltages or currents are too low in relation to noise Symbol 5 is no 5 CED displayed inst
13. atteries and accumula tors 20 OPERATING MANUAL MRU 20 version 3 0 7 Technical data e Specified accuracy relates to terminals of the meter e m v abbreviation indicated standard measured value 7 1 Basic data Measurement of resistance to earth Re Measurement method technical according to IEC 61557 5 Test range according to IEC 61557 5 0 500 1 99kQ for Un 50V 0 680 1 99kQ for Un 25V Ranges Resolution Basic uncertainty of displa 0 00 9 990 10 0 98 90 2 m v 100 9990 1 00 1 99kQ 0 01kQ e In the three pole method the uncertainty caused by resistance of probes is calculated and di splayed by the meter It can also be estimated using the following chart 100 0000 4 Ry RE 3000 10 0000 R Re 1000 R Re 300 1 0000 R Re 100 R Re 30 0 1000 Ry Re 10 Ry Re 3 _ Current electrode resistance Ry Re 1 0 0100 R Earth resistance Ry Re 0 3 Additional uncertainty caused by resistance of probes 0 0010 10 100 1000 10000 100000 Voltage electrode resistance Rs Q Influence of the resistance of electrodes on measure
14. ead of the result OF F In function the factory value of wiring resistance was restored Autozeroing of wires was turned off by the user Indication of battery level u UJ Batteries or rechargeable batteries charged d Batteries low After replacing batteries rechargeable batteries set the type of power supply in order to enable correct display of battery charging level charging characteristics of batteries and rechargeable batteries are different bf Discharged batteries or rechargeable batteries prevent stable oporation of the device Replace batteries or recharge rechargeable batteries Error detected by self monitoring MRU 20 devices are often exposed to strong electromagnetic interference which Err and error number may affect the content of internal registers The meter automatically controls some displayed on main field parameters and if necessary displays error messages Error message may by cosed of the display by temporary influence of external factors Therefore turn off the device and turn it back on If the problem persists the meter should be serviced OF and A Acceptable temperature inside the meter is exceeded SONEL SIA Wokulskiego 11 St 58 100 Swidnica Poland T 48 74 85 83 860 48 74 85 83 800 fax 48 74 85 83 808 http www sonel pl e mail export sonel pl
15. emory even after turning off the meter OPERATING MANUAL MRU 20 version 3 0 15 3 Power supply of the meter 3 1 Monitoring of the power supply voltage The level of the charge of the batteries or rechargeable batteries is currently indicated by the symbol in the right upper corner of the display SII Batteries or rechargeable batteries charged d 3 Batteries or rechargeable batteries low Batteries or rechargeable batteries need charging Note e The symbol bAt displayed on the display indicates insufficient power supply voltage and the need to charge or replace batteries e Measurements carried out with insufficient meter power supply voltage are distorted with additio nal 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 3 2 Replacement of batteries rechargeable batteries MRU 20 Meter is powered by eight batteries or rechargeable batteries R6 it is recommended to use alkaline batteries Batteries rechargeable batteries are inserted into a container in the bottom part of the casing WARNING Before replacing the batteries or rechargeable batteries disconnect the test leads from the meter In order to replace batteries or the set of rechargeable batteries it is necessary to do the following 1 Remove all the test leads from the measurement circuit and turn the meter off 2 Remove the batte
16. er and its case 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 pa stes etc Clean the probes with water and dry it Before the probes are stored for a prolonged period of time it is recommended to grease them with any machine lubricant The reels and test leads should be cleaned with water and detergents and then dried The electronic system of the meter does not require maintenance 5 Storage The following recommendations must be observed to ensure proper storing of the device e Disconnect all the test leads from the meter e Clean the meter and all its accessories thoroughly e Wind the long test leads onto the reels e the meter is to be stored for a prolonged period of time the batteries must be removed from the device e inorder to prevent total discharge of the rechargeable batteries during prolonged storage charge them from time to time 6 Dismantling and utilization Worn out electric and electronic equipment should be collected selectively i e it must not be di sposed with waste of another kind 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 b
17. higher than 60kQ an electrode or elec Please check connections in the measuring circuit or re duce the resistance of the measuring probe by its reposi tioning E Uncertainty of Re measurement introduced by the resi and the measure stance of test probes exceeds 30 Reduce the resistan A ce of the probe by its repositioning or increase the damp ness of the ground in the direct vicinity of the probe mE Resistance of test probes is higher than 50kQ but lower than 60kQ Interference voltage is above 10V or unstable measure NOISE ment result or measured voltages or currents are low in re lation to noise nm and Ab and Measured voltages or currents are too low in relation to long audio signal noise or very unstable measurement result Symbol oM nm Sis displayed instead of the result Acceptable temperature inside the meter is exceeded 2 2 Measurement of resistance using double pole method 1 as m Turn the meter Set the rotational function se lector at Re 2p position trodes and OPERATING MANUAL MRU 20 version 3 0 2 SET UsingUn button set test voltage C on 25V or 50V U on y After 5 sec the meter returns to the measu rement mode i You can also confirm the Li choice by pressing the START push button Connect the measured object to terminalsE and H of the meter 4 The meter is ready for measurement Uy
18. isplayed instead of the result Acceptable temperature inside the meter is exceeded 2 3 Measurement of the resistance of protective conductors and equipotential bondings Attention When carrying out measurements of very low resistance or when using leads other than original 1 2 m and 2 2 m the calibration of test leads must be performed W Turn on the meter Set the rotational function se lector at Rconr 200mA posi tion Rap GE OPERATING MANUAL MRU 20 version 3 0 11 Connect the measured object to terminals S and E of the meter The meter is ready for measurement Press START button Carry out the measurement Read out the result nn o Note test current flows unidirectionally To obtain results of a bidirectional current flow the measurement should be repeated with replaced test leads and then respective arithmetic mean should be calculated from both measurements 12 OPERATING MANUAL MRU 20 version 3 0 Additional informations displayed by the meter Interference voltage is too high gt 3Vrms the measure 4 A ment is impossible and Turn off the source of interferences gt and A Interference voltage is above 50V Immediately disconnect the meter and continuous audio Before re connecting turn off the source of voltage signal o gt 1990 RcoNT measuring range is exceeded Interference voltage with value of 1 3Vrms during RcoNr NOISE measurement
19. lations and specifications defined by the producer MRU 20 meter is designed to measure earth resistance and the resistance of protective conduc tors 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 The meter must be operated solely by appropriately qualified personnel members holding re quired certificates for carrying measurements in electric installations Unauthorized use of the me ter may result in its damage and may seriously endanger unauthorized user Using this manual does not exclude the need to comply with occupational health and safety regu lations and with other relevant fire regulations required during the performance of a particular type of work Before starting the work with the device in special environments e g potentially fire risk explosive environment it is necessary to consult it with the person responsible for health and safety It is unacceptable to operate the following damaged meter which is completely or partially out of order ameter with damaged test leads insulation a meter stored for an excessive period of time in disadvantageous conditions e g excessive humidity If the meter has been transferred from a cool to a warm environment of a high level of relative humidity do not carry out measurements until the meter is warmed up to the am bient temperature a
20. lay field for Information on completed measurement result 7 gt w H H compensation of test leads 2 j ni resistance CV Unit and type of displayed value ohms kilo onms resistance percentages additional error V volts interference voltage S gt ner OPERATING MANUAL EARTH RESISTANCE METER MRU 20 SONEL SA ul Wokulskiego 11 58 100 widnica Version 3 0 18 06 2014 The MRU 20 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 2 OPERATING MANUAL MRU 20 version 3 0 2 202 2 3 2 4 2 4 1 2 4 2 3 1 3 2 3 3 T E2 Rad 8 1 8 2 CONTENTS EEEE ENE ai 5 MEASUREMENTS erue crane e deo Essa pia ie ue pe EIE 6 MEASUREMENT OF RESISTANCE USING THREE POLE METHOD 6 MEASUREMENT OF RESISTANCE USING DOUBLE POLE METHOD 9 MEASUREMENT OF THE RESISTANCE OF PROTECTIVE CONDUCTORS AND EQUIPOTENTIAL BONDINGS ccccsccsscsscsccsccscesccnccsscescescessessesscsscusceseeseenss 11 CALIBRATION OF TEST EBADS R ROCA GEE 13 Activation OJ AULOZETOING eas 13 Switching off Autozeroing cccccccccccccnnsssscccccccaaaenseeccceccaaaasseecceesauaussceseeseaas 14 POWER SUPPLY OF THE METER
21. ment uncertainty OPERATING MANUAL MRU 20 version 3 0 21 Measurement of auxiliary electrodes resistance RH Rs Ranges 000 9990 1 00 9 99kQ 0 01kQ 5 Rs Re Ry 3 digits 10 0 50 0kO Measurement of interference voltages Internal resistance approx 100kQ Basic uncertainty 0 100V 2 m v 3 digits Measurement of Measurement method technical Test range according to IEC 61557 4 0 13 199 0 00 9 990 0 010 10 0 99 90 2 m v 3 digits 100 199Q Note Only values containing tolerances or boundary values are considered as guaranteed data Va lues without tolerances are for informational purposes only Other technical data em t m lt lt 22 LY PSO INSUIALON c eec e iR ERO COR double according to EN 61010 1 and IEC 61557 measurement nnne nnns IV 300V according to EN 61010 1 degree of housing protection acc to EN 60529 wia IP54 maximum voltage of interferences at which Re measurement is performed 24V maximum voltage of interferences at which Rconr measurement is performed 3V maximum measured voltage of interferences 100V re OS CUNT CIN a ara PRO Ac AA SRA ROG 125 Hz LOSE VOIAG G Reverse EE ii TO a LL 25V or 50V
22. nal result It is calculated on the basis of measured valued If such additional uncertainty exce eds 30 the following symbol is displayed with the measurement result Er You can improve the contact between the probe and soil for example by dampening with water the place where the probe is driven into earth driving the probe into earth in a different place or using a 80 cm long probe Check also the test leads for possible insulation damage and for corroded or loosened connection be tween the banana plug and the test lead In majority of cases the measurement accuracy achieved is satisfactory However you should always be aware of the uncertainty included in the measurement Calibration performed by the manufacturer takes into account the resistance of supplied measure ment lead of 2 2 m 8 OPERATING MANUAL MRU 20 version 3 0 Additional informations displayed by the meter Interference voltage is too high gt 24V the measure ment is impossible Turn off the source of interferences or try arrange probes different Interference voltage is above 50V Immediately disconnect the meter Before re connecting turn off the source of voltage and continuous audio signal o Interference voltage is above 100V Immediately disconnect the meter and continuous audio Before re connecting turn off the source of voltage signal o Interruption in measuring circuit or resistance of test pro F with the name of bes ic
23. pproximately 30 minutes Before commencing measurements make sure the test leads are connected to the appropriate measurement sockets Do not operate a meter with an open or incorrectly closed battery compartment or power it from sources other than those specified in this manual The inputs of the meter are protected electronically against overload e g due to having been con nected to a live circuit for all combinations of inputs up to 276V for 30 seconds Repairs may be carried out only by an authorized service point The device meets the requirements of standards EN 61010 1 and EN 61557 1 4 5 Attention The manufacturer reserves the right to introduce changes in appearance equi pment and technical data of the meter Note An attempt to install drivers in 64 bit Windows 8 may result in displaying In stallation failed message Cause Windows 8 by default blocks drivers without a digital signature Solution Disable the driver signature enforcement in Windows OPERATING MANUAL MRU 20 version 3 0 5 2 Measurements 2 1 Measurement of resistance using three pole method The three pole measuring method is the basic type of resistance to earth measurement Disconnect earth electrode being tested from the installation of the building Turn on the meter Set the rotational func tion selector set at Re 3p position Using Un button set test voltage on 25V or 50V After 5
24. regarding using Ni MH rechargeable batte ries If you do not use the device for a prolonged period of time then it is recommended to remove the rechargeable batteries and store them separately Store the rechargeable batteries in a dry cool and well ventilated place and protect them from direct sunlight Ambient temperature in case of prolonged storage should not exceed 30 C If the recharge able batteries are stored for a long time in a high temperature then occurring chemical processes may reduce their lifetime NiMH rechargeable batteries are usually last for 500 1000 charging cycles This rechargeable batte ries reach their maximum capacity after being formatted 2 3 charge and discharge cycles The most important factor which influences the lifetime a rechargeable battery is the level of its discharging The deeper the discharge level the shorter lifetime of a rechargeable battery The memory effect is limited in case of NIMH rechargeable batteries These rechargeable batteries may be charged at any point with no serious consequences However it is recommended to dischar ge them completely every few cycles 18 OPERATING MANUAL MRU 20 version 3 0 During storage Ni MH rechargeable batteries are discharged at the rate of approximately 30 per month Storing rechargeable batteries in high temperatures may increase this rate even to 60 In order to prevent excessive discharge of rechargeable batteries after which it would
25. ry compartment in the bottom of the case after loosening three screws 3 Replace all batteries rechargeable batteries New batteries or rechargeable batteries must be inserted observing the correct polarity on the springy part of the contact plate Incorrect posi tion of batteries will not damage the meter or batteries but the meter with incorrectly inserted bat teries will not work 4 Insert the battery compartment and fix it with screws 16 OPERATING MANUAL MRU 20 version 3 0 After replacing batteries rechargeable batteries the meter af ter switching it on will operate in power supply selection mode Ac Selected power supply rechar geable batteries gt Pressing SEL push button will change the power supply to r batteries SET bAt sz Another pressing of the push button will switch r the selection again to rechargeable batteries OPERATING MANUAL MRU 20 version 3 0 17 Pressing START push button will confirm the choice and the meter will be ready for measurement NOTE After replacing batteries rechargeable batteries set the type of power supply in order to enable correct display of battery charging level charging characte ristics of batteries and rechargeable batteries are different NOTE If batteries leak inside the battery compartment the meter should be serviced Rechargeable batteries should be charged in an external charger 3 3 General principles
26. s during calibration 7 2 1 Re Measurement 7 2 1 1 Additional uncertainty caused by resistance of auxiliary electrodes ee 1504 15 107 R 9 100000 R M pa OO L oc E Re RH and Rs are values indicated by the meter in Q The above uncertainty is calculated by the meter and displayed as ER 7 2 1 2 Additional uncertainty caused by serial interference voltage Additional uncertainty Q 0 00 9 99Q 0 01Re 0 012 U 0 003U 2 10 0 99 9Q 0 001 0 05 U 0 001U 100Q 1 99kQ 0 001Re 0 5 U 0 001U 7 2 1 3Additional uncertainty caused by ambient temperature 0 25 digits C 7 2 1 4Additional uncertainties according to IEC 61557 5 Operational uncertainty or Reference conditions or Additional ope Designation significant parameter range of use uncertainty Reference Supply voltage J according to 7 2 1 3 according to the formula defined in 7 2 1 2 according to the formula defined in TaN Z E E EP Operational uncertainty B A LISJE where A basic uncertainty Serial 3 interference voliage Resistance of probes and From 0 to 100Rz but lt auxiliary earth electrodes 50kQ Es OPERATING MANUAL MRU 20 version 3 0 23 7 2 2 Measurement of RcoNr 7 2 2 1 Additional uncertainty caused by ambient temperature 0 15 C 7 2 2 2 Additional uncertainties according to IEC 61557 4
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