Multi MET-2 User manual

Thank youverymuchforselectingour clampearth tester.
Thismodelis complex instrument and employs averyreliable
mechanical/electronic design. Before you use your new
instrument, read this instruction manual completely and
familiarize yourself thoroughly with all functions. With proper
use and care, your tester will give you years of satisfactory
service.
MultiMeasuringInstrumentsCo.,Ltd.
Akihabaramurai-Bldg.7F,
1-26 Kanda Sakuma-cho,
Chiyoda-ku,Tokyo,101-0025 Japan
Tel:[phone]
Fax:[phone]
Clamp Earth Tester
MET-2
Instruction Manual

CONTENTS
1. General………………………………………………………………………….....1
2. Safetysummary………………………………………………………………...2-3
3. Measuringprincipleof clamp earth tester……………………………………....4-5
4. Specification…………………………………………………………………….. 6-7
5. Paneldescription…………………………………………………….………......8-9
6. Preparation before use…………………………………………………………...10
6-1. Battery charging……………………………………………………………..10
6-2.Rechargeable battery………………………………………………........10-11
7. Operation…………………………………………………………………………12
7-1.AC current measurements………………………………………………….12
7-2.Earthresistancemeasurements………………………………………..13-14
7-3.Memoryfunction……………………………………………………........15-17
8. Measuringexample………………………………………………………......18-19
8-1. Electric installation…………………………………………………………...18
8-2. Earth resistance measurements for the outdoor appliance………………..20
8-3. Earth resistance measurements for multiple earth system………………...20
8-4. Earth resistance measurements for the earthing electrode………………..21
8-5.Earthresistancemeasurementsfor telecommunication system………….22
8-6. Measurements for the earting connection of the outlet…………………….22
9. Maintenance……………………………………………………………………...23
10. Warranty………………………………………………………………………….24

1. General
The periodic measurement of earth electrode resistance is indispensable to
ensurethe safetyforelectricalinstallation.
Theordinaryearth electrodetestmethodrequirestheuseof auxiliarytestspikes
orrodsforthemeasurements.
New clamp earth tester provides simple and quick measurements for earth
electrode resistance without lazy spiking work. The new spike-less method is
theloopmeasurementsbytheoperationoftwoclamps(CTs).
One CT injects a superimposing voltage into the circuit and the other CT
measures the injected current of the loop circuit. In our clamp earth tester, the
auto sweep signal (4kHz to 200kHz, 320mV p-p) is used and injected into the
loop circuit. When the resonance phenomenon is caused at the certain
frequency by the inductance and capacitance in the circuit, the current flow
becomes maximum. The injected current into the circuit is proportional to the
loop resistance.And this current is measured by CT and converted to the earth
resistancevalue.
Please refer to “chapter 3. Measuring principle of clamp earth tester”about
details.
Before you use MET-2, read this instruction manual completelyand understand
yourselfthoroughlywithallfunctions.
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WARNING
●The instrument is designed to measure for the low voltage circuit. Do not
makemeasurementsofpowerlinescarryingmorethanAC500V.
●POSSIBLE ELECTRICAL SHOCK. Do not make measurements if the
caseorCTisdamaged.
●POSSIBLEELECTRICALSHOCK orFIREHAZARD. Do not expose this
instrumentto rainormoisture. Donotoperatethetester in thepresenceof
flammablegassesorfumes.
●Never fail to keep the maximum tolerable input. Make measurements
withinthe ratedcurrent.
●Nevermakemeasurements withthecaseopened.
●Never operate this instrument if it becomes wet, damp or has any liquid
condensationbuild-uponanypartoftheinstrument.
●Nevermakemeasurements forun-insulatedconductorsorbusbars.
2. Safetysummary
This instrument has been manufactured and tested in accordance with safety
regulationsIEC61010-1/EN61010-1andIEC61010-2-032/EN61010-2-032.
If used for its intended purpose, safety of the user and of the instrument is
assured. The device may only be operated by properly trained personnel who
are capable of recognizing the dangers associated with the measurement of
electricalcurrentandvoltage.
Read the operating instructions completely and carefully before using the
instrument,andfollowallinstructionsincludedtherein.
Meaningofsymbolsontheinstrument:
Warningconcerningasourceofdanger
(Refertothe manual beforeuse.)
Theinstrumentisprotectedbydoubleorreinforcedinsulation
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CAUTION
●Do not use or storage the instrument under the direct sunshine, high
humidity and temperature, as it may cause the insulation defect of the
instrument.
●Donotusetheinstrumentnearbythe applianceormachinewhich generate
thestrongmagnetic field, as itmaycausethemeasuring errorof instrument.
●Donotapplythemechanicalvibrationorshocktotheinstrument.
●Before operating this instrument, familiarize yourself with all instructions
outlinedinthismanual.
●Always check to make sure that the function switch is set to the proper
position.
●When making measurements, use CAUTION as dangerous voltages may
bepresentinnormallysafeareas.
●To avoid electrical shock, use CAUTION when working above 60V DC or
25VACrms. Suchvoltagesposeashockhazard.
●Do not apply the voltage more than AC 10V to the input and output
terminals.
●DonotpulltheCTcable,as itmaycausedamages.
●Donotdisassembletheinstrument.
●If excessive current is applied to the CT, the instrument will be heated and
damaged. UsetheCTwithintheratedcurrent.
●The rechargeable batteries are used in the instrument. Do not mix with
normalbatteries,asitis verydangerous.
●The power supply voltage of battery charger is AC 200～240V. Do not
apply higher voltage to the charger, as it may cause the damage to the
instrumentandortheelectricalaccident.
●The charging batteries lose some of their capacity when repeatedly
charged/discharged. The actual decrease of capacity versus number of
chargingcyclesdependonbatterytype.

3. Measuring principle of clamp earth tester
Blockdiagram
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Equivalent circuit
The block diagram and equivalent circuit show the measuring principle of
CLAMPEARTHTESTER.
When the auto sweep signal (4kHz to 200kHz, 160mV p-p) is injected into the
circuit, the resonance phenomenon is caused at the certain frequency by
inductance (L) and electrostatic capacity (C0) or DC resistance (r) and
electrostaticcapacity(C1)inthecircuit,andthecurrentflow(i)iscaused. When
the resonance phenomenon is caused, the current flow (i) become maximum.
The injected current (i)into the circuit is proportional to the earth resistance (RB)
and this current (i) is measured by the measuring CT and used for the
computation of the earth resistance value (RB) with other calculation factors.
The resonance phenomenon is caused almost at 4kHz to 200kHzfrequency in
ourfieldtest.
Note: If the resonance phenomenon is not caused in the circuit, the current
flow (i2) is caused and the measured resistance value become RB+ RD
+Zc.This resistance value will be higher than the actual value
abnormally,oroverrangeindication“OVER”willbedisplayed.
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4. Specification
Measuringfunction : Earthresistance,ACcurrent(Load&leakage)
A/D conversion : Dualslopeintegrationmode
Safetystandard : IEC61010-1,IEC61010-2-032
InstallationCATⅡ600Vor CATⅢ300V
Sampling : Approx.2times/secondforAC current
Measuringtime : Approx.30secondforearthresistance
Display : LCD16letters/charactersx2linewithcontrast
adjuster
Overrangeindication : “OVER” on LCD
Lowbatteryindication : “B” mark on LCD
Dataholdindication : “DH” mark on LCD
Memoryfunction : 200measuringdatacanbestoredand recalled
Accuracy(23°C±5ºC,80%RHorless):
Earthresistance(Earthcurrent: Less than1A)
Range
Resolution
Accuracy
10Ω
0.01Ω
0.1～1Ω: ±0.1Ω
1～10Ω: ±0.5Ω
300Ω
0.1Ω
10～50Ω: ±2.0Ω
50～150Ω: ±5.0Ω
150～200Ω: ±20Ω
200～300Ω: ±30Ω
Note: Accuracy is specified by standard resistance with following test configuration.
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InductionCT
MeasuringCT

AC current
Range
Resolution
Accuracy
Maximumimput
200mA
0.1mA
3% rdg±8dgt
20Arms
2000mA
1mA
2% rdg±8dgt
20A
0.01A
2% rdg±8dgt
MeasuringCT : φ34mm with 2.5m lead
InjectionCT : φ34mm with 2.5m lead,
Autosweepsignal : 4kHz～200kHz
Signalinjectionlevel : Approx.320mVp-p
Operatingtemperature : 0°C～40°C, <85%RHwithoutcondensation
Storagetemperature : -10°C～60°C,<80%RHwithoutcondensation
Limitation of circuit voltage : LessthanAC500Vrms
Withstandingvoltage : AC 3700V 1 minute (between CT core and CT
handle)
Insulationresistance : More than 100MΩ (between CT core and CT
handle)
Powersupply : NiMH batterypack(1.2Vx5),
Batterycharger : AC200V-240V(50/60Hz)
Autopowerofffunction: Approx.5minuteslaterafterpoweron
Powerconsumption : Approx.400mA(Earthresistancemeasurement)
Batterylife : Approx.350timesmeasurementsunderfullcharged
condition
(Subjecttothetimesofcharging&discharging)
(Size &weight)
MeasuringCT : 90.5(W)x165(H)x38(D)mm,approx.460g
InjectionCT : 90.5(W)x165(H)x38(D)mm,approx.440g
Mainunit : 190(W)x140(H)x42(D)mm,approx.800g
Accessories : MeasuringCT………………..1
Injection CT………………….1
Battery charger……………....1
Carrying case………………..1
Subsidiary lead wire………....1
Instruction manual…………...1
Option: Outlet Checker……………….1
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5. Paneldescription
①Powerswitch : PowerON/OFFswitch. Afterthefinalkey
(POWER) operation, the power will be turned off
automatically5minuteslater.
②TerminalforInjectionCT : TheinsertionterminalfortheinjectionCT.
(INJECTION) Connectredplugtotheredterminalandblack
plugtotheblackterminal.
③TerminalformeasuringCT: TheinsertionterminalforthemeasuringCT.
(INPUT) Connectredplugtotheredterminalandblack
plugtotheblackterminal.
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④Menuswitch : Pressthisswitchtoreturntothedefaultdisplay.
(MENU)
⑤Enterswitch : Enterswitchforthemeasuringfunction(earth
(ENT) resistanceorcurrent)selectedby“UP”and
“DOWN”key. Also,usedtostarttheearth
resistancemeasurement.
⑥Up,downkeyswitch : Upanddownkeyswitchforthecursorofthe
(UP,DOWN) display.
⑦Data holdswitch : InAC currentmeasurement,pressthisswitch,
(DATAHOLD) “DH”markisdisplayedandthedisplayedvalue
is held in the display. To release, press this
switchagain.
⑧Memoryswitch : ThisswitchisusedtostoretheDataHoldvalue
(MEM) intothememory.
⑨Display : LCD,16letters×2 lines
⑩Knobfordisplaycontrast : Contrastadjustmentofthedisplay.
(CONTRAST)
⑪Chargerlamp : Duringbatterycharging,thislampisalwayslit.
⑫Jackforcharger : Inputjackforchargerplug.
(CHARGER)
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6. Preparation before use
6-1.Batterycharging
①Connect the charger plug to the jack
(CHARGER)of theinstrument.
②Connect the charger to AC outlet
making sure that main voltage is
compatible(AC200V～240V).
Thechargerlampis turnedONandthe
batterychargingwillstartimmediately.
③Charging of the battery takes 8 hours. Take care for over charging as the
chargerlampisnotturnedoff evenafter full charging.
6-2.Rechargeablebattery
NiMH battery is affected by various condition, and instrument operation time
maybeaffectedbythecharging/dischargingcyclesandcondition.
Precautiononchargingofbatteryunusedfora longperiod oftime:
●Charge the battery at least once per 6 months, otherwise the battery power
willbeexhausted.
●When the battery unused for a long period of time, the battery may not be
charged sufficiently.
●Keeptheinstrumentatdryplace. -10 -
CAUTION
●Use only charger delivered from manufacture or distributor of the test
instrumenttoavoidpossiblefireorelectricshock.
●Donotchargealkalinebattery.

●Whentheinstrumentisunusedforalongperiodoftime,thebatterypowerwill
beconsumedbytheselfdischarging.
●Avoidovercharging,itmaydamagethebatterylife.
●Beforeusingtheinstrument,chargethebatterysufficiently.
●When instrument operation time is significantly reduced even after full
charging,replacethebatterytonewone,asthebatterypowerisexhausted.
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7. Operation
7-1.ACcurrentmeasurements
①Press “POWER”switch, the
poweristurnedON.
②Press “DOWN”key switch and
move the cursor to “Current”
position and press “ENT”key.
The tester is set to AC current
measurement mode as the
drawing.
③ConnecttheplugofmeasuringCTtothe“INPUT”terminal.
④Measurementofloadcurrent (Max.AC 20Arms)
Clamp the conductor of the circuit
undertest. Readthedisplayedvalue.
If the measured current is over range,
“OVER”is displayed.
If you made measurements in a dark
place orin a place where it is difficult to
see the readings, use “DATA HOLD”
switch.
Note: Clamp only one conductor of the
circuitto bemeasured.
⑤Measurementofleakagecurrent
a.Measurementofgroundingline
Clampthegroundinglineandreadthedisplayedvalue.
b.Measurementofsingle-phaseorthreephaseelectriccircuit
To measure a leakage current in a single-phase or three phase circuit,
clamp the all active conductors (e.g. L1, N or L1, L2, L3, N). Read the
displayedvalue.
If youmakemeasurementsin adark placeorinaplacewhereitisdifficultto
seethereadings,use“DATAHOLD”switch.
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Note: Press“MENU”switchtothereturntotheinitialdisplay.
7-2.Earth resistancemeasurements
①Press “POWER”switch, the power is turned
ON.
②Connect the plug of injection CT to the
“INJECTION”terminal.
Connect the plug of measuring CT to the
“INPUT”terminal.
③Clamp the grounding circuit under test by
twoCTsmakingsurethatthearrowmarksof
theCTsaresamedirection.
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CAUTION
●Theinputfrequencyislimitedto100HzforAC currentmeasurements.
●Thefrequencyvalueisnotdisplayedforlessthan3mAinput.
WARNING
POSSIBLEELECTRICALSHOCKORFIREHAZARD:
●The applicablecircuitvoltageislimitedtoAC 500Vrms. Beforemeasure-
ments,checkthecircuitvoltagetobemeasured.
●Nevermakemeasurementsforuninsulatedconductors.
●Never fail to keep the maximum tolerable input. Do not apply more than
AC 20ArmstotheCT.

④Set the cursor to “Current”position and
press “ENT”switch. The tester is set to AC
currentmeasurementmode.
Check the current value of grounding circuit.
If the measured current value is more than
1A,theearth resistanceisnotmeasurable.
⑤Press “MENU”switch to return to default
display.
⑥Set the cursor to “Earth Res.”Position and
press“ENT”switch .
⑦Set the cursor to “High”position and press
“ENT”switch.
⑧“Measuring”indication begins to blink and
themeasurementwillstart.
⑨After approx. 30 seconds, the measured
value willbedisplayed.
Note: ●Press “MENU”switch to return to the
defaultdisplay.
●When making the successive mea-
surement, the waiting time is provided
for the stabilization of the circuit, but
thisisnotabnormal.
●When “Lower Range”is displayed at High range measurement, reset
therangeto“Low”andmeasureagain asfollows:
a.Press“MENU”switchto returntothe defaultdisplay.
b.Setthecursorto“EarthRes.”positionandpress“ENT”switch.
c.Setthecursorto“Low”positionandpress“ENT”switch.
●ThecorrectmeasurementshouldbestartedfromHighrange.
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7-3.Memoryfunction
(1)Howtostore the dataintothememory
①AftermeasurementforAC currentorearth
resistance, press “DATA HOLD”switch.
The measured data is held with “D.H”
mark, the data number and the memory
blocknumber.
②Press “MEM”switch, “Writing Data!”is in-
dicated and the helddataisstored into the
memoryandthedatanumberis renewed.
(2)Changeofmemoryblocknumber
To store the measured data into the different
memory block, change the memory block
numberasfollows.
①Press “MENU”switch, the default display
is indicated.
②Press “DOWN”switch twice and set the
cursorto“Memory”position.
Press“ENT”switch,“B/N”isindicated.
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CAUTIONfor earthresistancemeasurement
●Besureto clampthegroundinglinebyboth InjectionCTandMeasuringCT
with thesamedirection of the arrow mark. If incorrectdirectionisused, the
measuringerrorwillbecausedorabnormalvaluewillbedisplayed.
●Thegroundingcircuitwithmorethan1Acurrentflowisnotmeasurable.
●This instrument measures the earth resistance using the resonance
phenomenon caused by L (Inductance) and C (Capacitance) in the circuit.
Whenthemeasuredresistance valueisabnormalhigher thantheestimated
value, there is a possibility that the resonance phenomenon is not caused.
Insuchcase,useasubsidiaryjumperwiretocreateagoodloopcircuit.
Datanumber Memoryblocknumber
Defaultdisplay

③Setthe cursor to “B/N”positionby “UP”or“DOWN”keyswitch. Press “ENT”
switch,thecurrentmemoryblocknumberisindicated.
④Press “UP”key switch to change the memory block number. Afterchanging
thememoryblocknumber,press“ENT”switchforconfirmation.
Note: The memory block number is not changed downward. When failed to
change the memory block number, press “MENU”switch without
pressing “ENT”switch, to return to the default display, and try again
aboveprocedure.
(3)Recallof thestored data
①Press “MENU”switch, the default
displayis indicated.
②Set the cursor to “Memory”position by
pressing “DOWN”key switch twice.
Press “ENT”switch, “Display”is
indicated.
③Set the cursor to “Display”position by
“UP”or “DOWN”key switch and press
“ENT”switch, the stored data is recalled
withthedatanumber.
④Press“UP”or“DOWN”keyswitchtoscrollthestoreddatamemory.
(4)Erasureofthememory
Themaximummemorysizeis200data.
Tostorethenewdata,erasetheallmemory.
①Press “MENU”switch, the default
displayis indicated.
②Set the cursor to “Memory”position by
pressing“UP”or“DOWN”keyswitch.
Press“ENT”switch,“Clear”isindicated.
③Set the cursor to “Clear”position by
“UP”or “DOWN”key switch, and press
“ENT”switch,“Yes”or “No”isindicated.
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Datanumber Memoryblocknumber

④Setthecursorto “Yes”by“UP”or“DOWN”keyswitchandpress“ENT”switch,
theallmemoryiserased.
Toescapefromtheclearmode,setthecursorto“No”andpress“ENT”switch.
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5. Measuring example
The various measuring examples are showed in this chapter, however, these
are potential sources of error or incorrect test results due to the difference of the
earthing system and configuration in the field. It is important to remember the
keyrulesforthecorrectmeasurements.
●Theremustbealoopresistancetomeasure.
●Theearthpathmustbeinloopcircuit.
●TheremustbeL(inductance) andC (capacitance)inaloopcircuit.
8-1.Electric installation
“ ” isshowstheclampingpointof theinjectionCT and themeasuringCT.
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