Instruction Manual
Contents
1. Vrms Vavg Vrms Vavg sensing instrument 7 an 0 1 414 0 707 0 637 1 111 1 400 11 1 0 5Ax1 111 100 1 114VD 1 100 4 Instrument layout O Name of each parts and buttons for MODEL4200 and KEW4202 Transformer jaw Trigger Backlight button Switches on off the backlight Function button Switches ACA Earth resistance functions Memory mode button Check the measured value by Data number Data hold button Freezes releases the fixed da O n Kew EARTH MODEL 4200 Turns on off the instrument Display unit LCD Cursor button UP Selects data number to save the measured value or to view 2806 2 8 the measured data in memory gefale fak Cursor button DOWN Selects data number to save the measured value or to view the measured data in memory Save button Saves the measured value ol KYORITSU gt Ni Symbols to be displayed the LCD Displayed when saving the measured value or when Data number instrument is in memory mode 1 to 100 Displayed when batteries are exhausted Displayed at Earth resistance function when Transformer jaws are not properly closed Displayed at Earth resistance function when current or noise that affects on the measured value presents Displayed when data hold function is activated Displayed when ACA function 15 selected 1 Displa2. is not displayed at the upper left on the LCD Press the trigger to open the Transformer jaws and close them over one conductor only Measured current value is displayed on the LCD Earth leakage current that flows through an earthed wire can be measured by this method 7 2 Measurement of balance leakage current Press the Function button and select the ACA function Confirm the displayed unit is and the MEM is not displayed at the upper left on the LCD Clamp onto all conductors except for the earthed wire Measured current value is displayed on the LCD E O o o Single phase 2 wire system Three phase 3 wire system In 3 wire system with neutral In 4 wire system with neutral clamp onto all 4 wires clamp onto all 3 wires 7 3 Measurement of earth resistance A CAUTION Follow the procedure described in 7 1 Normal measurement of current and measure the current flowing on the earthed wire prior to the measurement of earth resistance In case that the symbol is displayed at the upper right of the LCD it means that a great error would be included in the measured result To avoid such inaccurate measurement reduce the current flowing on the earthed wire by turning off the device from which current is applied to the earthed line under test Measurement cannot be made for the earth without multi earthing system or when
3. automatically switches to the next available data number present data number 1 and the next measured value can be saved to it The data number returns to 1 after the measurement result is saved to the data number 100 lt gt When the new measurement result is saved to the data number on which the previous measurement result is saved previous data will be overwritten lt gt When saving a data while the data hold function is activated the readings which is being held on the LCD will be saved O Recalling the measurement results memory To activate the memory function press the Memory mode button Then MEM is displayed on the LCD Pressing the Cursor button a or y changes the data number displayed on the LCD and the measurement result in memory is displayed accordingly lt gt To disable the memory mode press the Memory mode button again or press the Function button BY Then MEM symbol disappears Bars are displayed for the Data number that does not contain any test result O Clearing the measurement results in memory To clear the measurement result press the Save button with the Memory mode button pressed down The message cir is displayed on the LCD for about 2 seconds and the measurement result on the selected data number is cleared Then the indication on the LCD becomes lt gt Follow the procedure below to delete the all measurement results 1 Press the Power
4. button while the instrument is off while the Memory mode button and the Save button are being pressed down Then release the Power button only 2 Instrument is turned on ALL and cir are displayed on the LCD for about 2 sec Now all the stored data are deleted A 8 6 Bluetooth Communication Function KEW4202 only KEW4202 can perform data communication between Android devices Bluetooth communication Notes on using Bluetooth function This function is not available on MODEL4200 but available on KEW4202 Before starting to use this function download the special application KEW Smart from the Internet site Some of the functions are available only while connected to the Internet For further details please refer to 11 KEW Smart Functions or Help for KEW Smart WARNING Radio waves at Bluetooth communication may affect the operations of medical electronic devices Special care should be taken when using Bluetooth connection in the areas where such devices are present Cautions O The maximum Bluetooth communication distance is approx 10m However it may be shortened if there are obstacles such as walls doors or people or depending on the radio wave condition or environment of usage O Using KEW4202 or Android devices near wireless LAN devices IEEE802 11 b g may cause the radio interference lowering of communication speed resulting in significant time lag in
5. local KYORITSU distributor for repair or recalibration For repair the resistor for operation check shall be attached and returned together with the instrument Resistor for operation check 1 l at q I 10 loop 100 loop Resistor for operation check Allowable range 9 Measuring method A DANGER Never make measurement on a circuit in which the electrical potential exceeds AC300V Transformer jaws are made of metal and their tips are not completely insulated Be especially careful about the possible shorting where the equipment under test has exposed metal parts Never make measurement with the Battery cover removed Do not measure a current over 30A Transformer jaws may heat to cause a fire or deformation of molding parts which will degrade insulation When clamping the conductors on which over 30A flowing and ffi is displayed on the LCD stop measurement immediately and take off the instrument from the conductor under test CAUTION Take sufficient care not to apply shock vibration or excessive force to the jaw tips Otherwise precisely adjusted Transformer jaws will be damaged This instrument performs self calibration for about 3 seconds when it is turned on EAL is displayed on the LCD Do not clamp onto any conductor or open the jaws in this period Otherwise inaccurate measurement may occur When foreign substances are stuck in the jaw tips or they are
6. marked inside When the battery voltage warning symbol is displayed on the upper left of the LCD replace the batteries Note that the display blanks and symbol is not displayed if the batteries are completely exhausted 1 Stop measurement when the warning symbol appears and um clamp from the object under test 2 Ensure that the instrument 18 powered off 3 Loosen the Battery cover fixing screw on the back of the instrument Then remove the Battery cover 4 Install new batteries LR6 or R6P 4pcs in correct polarity as marked inside 5 Put the Battery cover in place and tighten the screw 10 Pairing with Bluetooth compatible devices KEW4202 is necessary to perform the pairing procedure to connect KEW4202 and Android devices via Bluetooth communication O if the symbol is displayed on the LCD of KEW4202 replace the batteries with new ones before performing the pairing procedure 1 Power on KEW4202 2 Power on the Android device and find the Setting menu Look for the Bluetooth setting in the Wireless Setting menu 3 On the Android device choose Search for Bluetooth Devices The model name 4202 will be displayed on the screen The X s behind the model name 15 the serial no of the unit 4 Select and pair the device If the pairing setting fails please check the following points Distance between KEW4202 and the Android device Move them closer and p
7. not properly engaged the Transformer jaws do not fully close In such a case do not release the jaw trigger abruptly or attempt to close the Transformer jaws by applying external force Make sure that the jaws close by themselves after removing the foreign substance or making them free to move The size of a conductor can be tested is 30mm in diameter Accurate measurement cannot be made on a conductor larger than this because the Transformer jaws cannot fully close Never attempt to apply excessive force to close the jaws When measuring large current the Transformer jaws may buzz This has no effect on the instrument s performance or safety Sensitive Transformer jaws are used for this instrument Because of the characteristics of Transformer jaws which can be opened and closed it is impossible to eliminate the interference of external magnetic field completely If there are something which generating large magnetic field at a nearby site current value can be displayed O may not be displayed before clamping on the conductor For such a case please use the instrument at a location far from the thing which generating magnetic field Following are the typical things generating magnetic field Conductor fed large current Motor Equipment which has magnet Integrating wattmeter 7 1 Normal measurement of current Press the Function button and select the ACA function Confirm the displayed unit is mA and the MEM
8. the Transformer jaws fitted parts and Case enclosure except for jaws 5OMQ or more at 1000V Between the Transformer jaws fitted parts and Case enclosure except for jaws Approx 32mm in diameter max 246 L x 120 W x 54 D mm Approx 780g including batteries Battery R6P 4pcs MODEL4200 4 KEW4202 Instruction manual Resistor for operation check MODEL8304 Hard case MODEL9166 MODEL4200 MODEL9167 1pce KEW4202 Most alternating currents and voltages are expressed in effective values which are also referred to as RMS Root Mean Square values The effective value 15 the square root of the average of square of alternating current or voltage values Many clamp meters using a conventional rectifying circuit have RMS scales for AC measurement The scales are however actually calibrated in terms of the effective value of a sine wave though the clamp meter is responding to the average value The calibration is done with a conversion factor of 1 111 for sine wave which is found by dividing the effective value by the average value These instruments are therefore in error if the input voltage or current has some other shape than sine wave O CF Crest Factor is found by dividing the peak value by the effective value Examples Sine wave CF 1 414 Square wave with a 1 9 duty ratio CF 3 Reference Reading errors Waveform Effective value a value Crest factor for average a
9. the earth resistance under test is smaller than the other earth resistances To avoid inaccurate reading may be taken never make a measurement for the TS arth system with multiple units of this instruments The Y symbol may be displayed during a measurement of earth resistance It indicates that the jaws of the instrument are not properly closed Measurement is being stopped while this symbol is displayed on the LCD Close the Transformer jaws properly to re start the measurement Response time at Earth resistance function is about 7 seconds It takes awhile until the readings become stable Measurement procedure Press the Function button and select the Earth resistance function Confirm the displayed unit is and is not displayed at the upper left on the LCD Press the trigger to open the Transformer jaws and close them over the earthed wire under test Measured resistance value 15 displayed on the LCD lt Noise check function gt At the Earth resistance function the 93 symbol is displayed on the LCD in the following cases which may effect on a measurement The current flowing on the earthed wire 15 exceeding the following value Range of Earth resistance function Allowable current value 200 2 or less 2000 6000 12000 400mA or less The current flowing on the earthed wire includes a harmonic wave which effects on the measurement lt Jaws check f
10. 00 Precision measurement shall be performed with our Earth resistance tester M 4102A or M 4105A for the measurement of single earthed wire Measurement example using M 4102A Earthed electrode Auxiliary earth spikes under test 6 Getting started A CAUTION This instrument performs self calibration for about 3 seconds when it is turned on EARL is displayed on the LCD Do not clamp onto any conductor open the jaws in this period Otherwise inaccurate measurement may occur 1 Check the battery voltage When nothing is displayed on the LCD press the power button and turn on the instrument Battery voltage is enough when indication is clear and the symbol is not displayed on the LCD after turning on the instrument Follow the procedure described in 9 Battery replacement and replace the batteries with new ones when any of following symptoms is noted Otherwise accurate measurement and proper saving cannot be ensured symbol is being displayed indications are faint and difficult to read nothing is displayed on the LCD 2 Verify the correct measurement of earth resistance Clamp on the supplied resistor for operation check as shown below and verify that the Transformer jaw and the circuit works correctly When the indicated value is within the range described below they are operating correctly If the indicated value 15 greatly exceeding the accuracy send the instrument to your
11. INSTRUCTION MANUAL MODEL4200 KEW4202 DIGITAL EARTH CLAMP TESTER MODEL 4200 KEW 4202 KYORITSU ELECTRICAL INSTRUMENTS WORKS LTD Contents i Sy War ill8S Uu uuu u 1 2 Features 1 u u u u 3 Mo A 4 de T mir y sien 6 5 Measurement principle station ice T Gening stared A 9 Le Measuring method sonado litros 10 7 1 Normal measurement Of current 11 7 2 Measurement of balance leakage current 11 7 3 Measurement of earth resistance 12 8 Other functionS serenata 13 8 1 Auto power off function a 13 8 2 Data hold function 13 0 3 B uzzer IOBIC IOf serrana 13 8 4 Backlight sido 13 8 5 Memory function nt 14 8 6 Bluetooth Communication Function KEW4202 only 15 9 Battery replacement 17 10 Pairing with Bluetooth compatible devices KEW4202 18 11 Features of KEW Smart KEW4202 19 1 Safety Warnings This instrument has been designed manufactured and tested according to IEC 61010 Safety requirements for Electronic Measuring apparatus and delivered in the best condition after passing qu
12. ality control tests This instruction manual contains warnings and safety procedures which have to be observed by the user to ensure safe operation of the instrument and to maintain it in safe condition Therefore read through these operating instructions before using the instrument WARNING O Read through and understand the instructions contained in this manual before using the instrument O Keep the manual at hand to enable quick reference whenever necessary O The instrument is to be used only in its intended applications Understand and follow all the safety instructions contained in the manual It is essential that the above instructions are adhered to Failure to follow the above instructions may cause injury instrument damage and or damage to equipment under test The symbol N indicated on the instrument means that the user must refer to the related parts in the manual for safe operation of the instrument lt 15 essential to read the instructions wherever the symbol appears in the manual Z DANGER is reserved for conditions and actions that are likely to cause serious or fatal injury WARNING is reserved for conditions and actions that can cause serious or fatal injury CAUTION is reserved for conditions and actions that can cause injury or instrument damage O Following symbols are used on the instrument Attention should be paid to each symbol to ensure your safety A This symbol ind
13. andard IEC61010 1 CAT IV 300V Pollution degree 2 IEC61010 2 032 e This instrument is protected by double or reinforced insulation 0 Bluetooth Communication Function KEW4202 only Remote checking of measurements is possible without accessing KEW4202 unit by connecting KEW4202 and Android devices via Bluetooth 3 Specification range and accuracy 0 010 0 00 20 000 1 5dgt 2000 20 0 200 00 3 5det Earth resistance 200 399 200 3990 60 5 Auto ee 400 5990 10 10dgt 12000 100 600 126009 ony 0 0 100 0mA 1000mA 100 1000mA 2 5dgt 0 01A 1 00 10 00A sine wave Auto ranging 10 0 30 0A Crest factor 2 5 Accuracy at sine wave 1 5b0Hz 60Hz peak value shall exceed 60 In the following cases zero will be displayed on the LCD At 200 range of Earth resistance function 0 04 or less At 100mA range of ACA function 0 4mA less A range shifts to upper range when the input exceeds 105 of the selected range and shifts to the lower range when the input falls under 80 of the range O Operating system Earth resistance function Constant voltage injection Current detection Frequency 2400 7 Dual Integration AC current function Successive Approximation True RMS O Display Liquid crystal display with a maximum count of 2099 O Over range indication OL displayed when input exceeds the upper limi
14. be sent by E mail while the connection to KEW4202 is turned off Check on map Measured locations can be checked on the Google Map if the saved data includes GPS location On the Android device OPEN or NOISE warning will be displayed in conjunction with KEW4202 For further details please see Help for KEW Smart Cautions O Battery level of KEW4202 15 not shown on Android devices Ensure that the battery level of KEW4202 15 sufficient before starting to perform measurements using these features Replace batteries with new ones if necessary O Remote control such as switching functions or activating data hold of KEW4202 from Android devices is not possible 19 _ 90 DISTRIBUTOR KYORITSU ELECTRICAL INSTRUMENTS J WORKS LTD 2 5 20 Nakane Meguro ku Tokyo 152 0031 Japan Phone 81 3 3723 0131 Fax 81 3 3723 0152 URL http www kew ltd co jp E maill info eng Okew ltd co jp Factory Ehime Japan 4 12 92 2088
15. erform the pairing procedure again Bluetooth function on Android device Turn on the Bluetooth function on the Android device and try again Depending on your network connection it may take awhile to complete the pairing procedure 18 11 Features of KEW Smart KEW4202 Remote checking of measurements is possible without accessing KEW4202 using the special Android application KEW Smart The application KEW Smart is available on download site for free An Internet access is required Please note that communication charge is incurred separately for downloading applications and using special features of them For your information KEW Smart is provided on line only Features of KEW Smart O Remote checking of measurement is possible earth ground resistance and AC current values O Data hold function on Android devices O Save display measurement results Measured results can be saved with comments max 32 characters Save data includes measurement and GPS location while GPS feature has been turned on Comparator function earth ground resistance value Informs when the measured value is lower or higher than the preset value O Memory download function Downloads the saved data from KEW4202 by pressing the Memory mode Switch on KEW4202 This function can be used while the instrument is not performing measurements Features available using Internet connection O E mail Measured data can
16. g a measurement When the transformer jaws are worn to the wear line see the figure below stop the use of the instrument WARNING Never attempt to make any measurement if any abnormal conditions such as a broken cover or exposed metal parts are present on the instrument Do not install substitute parts or make any modification to the instrument Return the instrument to your local KYORITSU distributor for repair or re calibration Do try to replace the batteries if the surface of the instrument is wet Ensure that the instrument is switched off when opening the Battery cover for battery replacement Always be sure to keep your fingers and hands behind the Safety barrier see the figure below Otherwise user may be exposed to the danger of electrical shock CAUTION Press the Function button and confirm the appropriate function is selected before starting a measurement Do not expose the instrument to direct sunlight high temperatures and humidity or dew Press the Power button and turn off the instrument after use When the instrument will not be in use for a long period place it in storage after removing the batteries Use a damp cloth with water or neutral detergent for cleaning the instrument Do not use abrasives or solvents Take sufficient care not to apply shock such as drop Otherwise precisely adjusted Transformer jaws will be damaged Be careful not to pinch some foreign sub
17. icates that the user must refer to the explanations in the instruction manual E This symbol indicates that the instrument is protected by double or reinforced insulation This symbol indicates that this instrument can clamp on bare conductors This symbol indicates AC DANGER measurement a circuit in which the electrical potential exceeds A Do not make measurement when thunder is rumbling Stop measurement and take off the instrument from the object under test Do not attempt to make measurement in the presence of flammable gasses Otherwise the use of the instrument may cause sparking which can lead to an explosion To avoid electrical shock by touching the equipment under test 15 surroundings be sure to wear insulated protective gear Transformer jaws are made of metal and their tips are not completely insulated Be especially careful about the possible shorting where the equipment under test has exposed metal parts Never attempt to use the instrument if its surface or your hand is wet Do not exceed the maximum allowable input of any measuring range Do not measure a current over 30A Transformer jaws may heat to cause a fire or deformation of molding parts which will degrade insulation When clamping the conductors on which over 30A flowing and M is displayed on the LCD stop measurement immediately and take off the instrument from the conductor under test Never open the Battery cover durin
18. ices Communication with Android devices Measurement results of KEW4202 can be displayed on Android devices Bluetooth communication by using the special application KEW Smart Remote checking of measurements is possible without accessing KEW4202 1 Communication method Power on KEW4202 select a measurement function and then clamp onto the object to be measured Activate KEW Smart on the Android device and select the device to connect from the menu Touch the Start measurement button on the screen after the connection has been established Then the measured results will automatically be displayed on the Android device 2 Disconnection and Stop measurement Touch the Disconnect button on the screen to disconnect the communication Touch the Connect button to reconnect Touch the Stop measurement button on the screen to stop measurement In this case connection with KEW4202 will not be disconnected For various useful functions of KEW Smart please refer to 11 KEW Smart Functions or Help for KEW Smart 16 9 Battery replacement WARNING O In order to avoid possible shock hazard take off the instrument from the conductor under test and turn off the instrument before trying to replace the batteries AX CAUTION Do not mix new and old batteries Never use the different kinds of batteries at the same time O install batteries in correct polarity as
19. ks while the instrument is in the Data hold mode data hold is cancelled 8 3 Buzzer function This function is to give audible warning to user when the measured earth resistance is 100 or less To enable this function press the Function button at the earth resistance function at least 2 seconds The symbol is displayed at the lower left on the LCD Buzzer sounds when the measured earth resistance is 100 or less To disable the buzzer function press the Function button again Then the symbol disappears 8 4 Backlight function This function is to view the test results in dimly lit areas To switch on the backlight press the Backlight button while the instrument turned on To switch off the backlight press the Backlight button again lt gt Backlight is automatically switched off in about 1 minute to conserve battery power 45 8 5 Memory function This function is to save and display the measurement results O Saving the measurement results 1 Select any data number from 1 to 100 by using the Cursor button J or at ACA or Earth resistance function and save the measurement results lt gt When the Cursor button is being pressed down the number switches quickly 2 To save the measurement result being displayed on the LCD press the Save button E Then the result is saved to the selected data number MEM is displayed for about 1 second lt gt After saving the data data number
20. stances with the Transformer jaw tips Care should be taken not to pinch your fingers when opening or closing the Jaws Pass your hand through the Strap band and use the instrument Wear line 2 Features This instrument is a digital clamp on earth resistance tester and it is used in multi earthed systems Can measure the earth resistance by simply clamping around the earthed wires This instrument also equips AC current function to measure current up to 30A same as our traditional leakage clamp meters A single earthing cannot be measured only for multiple earthing system Wide measuring range Auto ranging Earth ground resistance Max 12000 Min resolution 0 010 AC current Max 30 Min resolution 0 1mA O Noise check function A function to detect current which effects on an earth resistance measurement and display the NOISE symbol on the LCD True RMS Accurate true RMS readings of AC current with distorted waveform Auto power off function A function to prevent the instrument from being left turned on and conserve battery power O Data hold function A function to freeze the measured value on the display O Buzzer function A function to give audible warning to the user when the measurement result 15 100 or less O Backlight function A function to facilitate working at dimly lit areas O Memory function A function to save and display the measurement result O Designed to following safety st
21. t of the measuring range O Response time Earth resistance function 7 seconds AC current function Approx 2 seconds Sample rate Approx once per second O Location for use Altitude 2000m or less Indoor outdoor use O protection degree IP40 O Temperature amp humidity range 23 C 5 Relative humidity 85 or less guaranteed accuracy no condensation Operating temperature amp 10C to 40 Relative humidity 85 or less humidity range condensation O Storage temperature amp 20 to 60 C Relative humidity 85 or less humidity range without batteries no condensation O Power source DC6V RP size AA manganese battery x 4pcs or LR6 size AA alkaline battery x 4pcs Current consumption MODEL4200 Approx 50mA max 100mA KEW4202 Approx 90mA max 140mA Measurement time MODEL4200 Approx 12 hours when using R6P or 24 hours when using LR6 KEW4202 Approx 5 hours when using R6P or 21 hours when using LR6 Auto power off O Applicable standards O External communication method Withstand voltage O Insulation resistance e Conductor size Dimension Weight O Accessories lt Supplemental remarks gt O Effective value RMS Turns power off about 10 minutes after the last button operation IEC61010 1 CAT IV 300V Pollution degree2 IEC61010 2 032 IEC61326 2 2 EMC standard Bluetooth Ver2 1 EDR Class2 AC5160Vrms 5 seconds Between
22. the display update rate between KEW4202 and Android device In this case keep KEW4202 and the Android device away from the wireless LAN devices or turn off the wireless LAN devices or shorten the distance between KEW4202 and Android device O lt may be difficult to establish communication connection if either KEW4202 or Android device is in a metal box In such cases change the measurement location or remove the metal obstacle between KEW4202 and Android device O f any leaking of data or information occurs while making a communication using Bluetooth function we assume no responsibility for any released content Communication with KEW4202 may not be established even if using Android device on which our special application operates In that case use the other Android devices and check for connection If you cannot confirm the connection there may be problem with KEW4202 unit Please contact your local KYORITSU distributor The Bluetooth word mark and logos are owned by Bluetooth SIG Inc and any use of such marks by Kyoritsu is licensed Android and Google Map are the trademark or registered trade mark of Google INC In this manual the TM or mark is not specified 15 Set up First set a Bluetooth connection pairing from an Android device For further details please refer to the instruction manual for the Android device Help for KEW Smart or 10 Pairing with Bluetooth compatible dev
23. unction gt The Y symbol is displayed when the Transformer jaws of the instrument not properly closed Measurement will be stopped when this symbol appears on the LCD _ 12 8 Other functions 8 1 Auto power off function This function is to prevent the instrument from being left turned on and conserve battery power The instrument automatically turns off about 10 minutes after the last button operation To return to the normal mode press the Power button again and turns on the instrument lt gt The buzzer sounds before the instrument turns off lt gt To disable the auto power off function follow the procedure below 1 Turn on the instrument by pressing the Power button with the Data hold button pressed down Then release the Power button only 2 The instrument is turned and PRFF is displayed on the LCD for about 1 second Now the auto power off function is disabled To enable the auto power off function again turn off and on the instrument without pressing the Data hold button 8 2 Data hold function This function is to freeze the indicated value on the display When the Data hold button is pressed once the indicated value on the LCD 15 fixed and does not change even though current under test varies The I symbol is shown at the upper right on the LCD To exit the Data hold mode press the Data hold button again f symbol disappears lt gt When the Auto power off function wor
24. yed when instrument is in continuity mode at Measured value Unit Earth resistance function 5 Measurement principle This instrument can measure the earth resistance to earth in multi earthed system Let s regard earth resistance under test as Rx and the other earth resistances as Ri R An IK Ta i in 1 K x Rx Ry R2 L Rn Of these earth resistances Ri R2 Rn can be considered that they are connected in parallel And can be regarded as a combined resistance Rs The Rs can be regarded small enough against Rx since a combined resistance consists of several resistances Following is an equivalent circuit diagram of this circuit By applying the Voltage V to the circuit from the Transformer jaw CT1 current is shall be flowed flowed corresponding to the earth resistance R can be put out by the calculation after detecting the current with the other Transformer jaw In this case R displayed in this instrument can be regarded as Rx because Rs can be regarded small enough against Rx R Rx Rs Rx Rs CAUTION This instrument is not supporting the measurement for the locations with following earth systems O Single earth that is not connected to other earths Lightning rod etc O Earth on which a current over 2A is measured at AC current function of this instrument O Earth with a larger earth resistance than an earth resistance of testing O Earth with earth resistance over 120
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