AEMC 6240 User manual

MICRO-OHMMETER 6240
ENGLISH User Manual
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Statement of Compliance
Chauvin Arnoux®, Inc. d.b.a. AEMC®Instruments
certifies that this instrument has been calibrated
using standards and instruments traceable to
international standards.
We guarantee that at the time of shipping your
instrument has met its published specifications.
An NIST traceable certificate may be
requested at the time of purchase, or obtained
by returning the instrument to our repair and
calibration facility, for a nominal charge.
The recommended calibration interval for this
instrument is 12 months and begins on the date of
receipt by the customer. For recalibration, please
use our calibration services. Refer to our repair
and calibration section at
Serial #: ________________________________
Catalog #: 2129.80
Model #: 6240
Please fill in the appropriate date as indicated:
Date Received: _________________________________
Date Calibration Due: _______________________
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Table of Contents
1. INTRODUCTION ................................................................................. 4
1.1 International Electrical Symbols ................................................5
1.2 Definition ofMeasurementCategories .....................................5
1.3 ReceivingYourShipment ..........................................................5
1.4 OrderingInformation .................................................................6
1.4.1 AccessoriesandReplacementParts ............................6
2. PRODUCT FEATURES......................................................................... 7
2.1 Description ................................................................................7
2.2 Applications ..............................................................................8
2.3 KeyFeatures ............................................................................8
2.4 ControlFeatures .......................................................................9
2.5 ButtonFunctions .....................................................................10
2.6 DisplaySymbols .....................................................................11
3. SPECIFICATIONS............................................................................. 12
3.1 Electrical .................................................................................12
3.2 Mechanical .............................................................................. 13
3.3 Environmental .........................................................................14
3.4 Safety ...................................................................................... 14
4. OPERATION..................................................................................... 15
4.1 PrecautionsBeforeUse .......................................................... 15
4.2 InstrumentConfiguration (SET-UPmode) ..............................15
4.3 ResistanceMeasurements .....................................................16
4.3.1 MeasurementReadings .............................................. 17
4.3.2 ConnectionsandReadings ......................................... 17
4.3.3 Test Lead Connection .................................................18
4.4 RepetitiveMeasurements .......................................................18
4.5 MeasuringVeryLowResistance ............................................19
4.6 AutomaticRecording ..............................................................20
4.7 StoringResultsintoMemory ...................................................21
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Micro-Ohmmeter Model 6240 3
4.8 RecallingResultsfromMemory .............................................. 22
4.9 ErasingMeasurementsfromMemory .....................................23
4.9.1 ErasingSelectedMeasurements ................................23
4.9.2 ErasingAllMeasurements ..........................................23
5. DATAVIEW®SOFTWARE................................................................... 24
5.1 InstallingDataView® ................................................................24
5.2 ConnectingtheInstrumenttoyourComputer ......................... 28
5.3 OpeningtheMicro-ohmmeterControlPanel ..........................29
5.4 Configuring theInstrument .....................................................30
5.5 DownloadingStoredTests ......................................................31
5.6 Saving/ExportingDatatoaSpreadsheetorPDFFile ............32
5.6.1 SavingDatatoSpreadsheetfromControlPanel ........32
5.6.2 ExportingDatatoaPDFfromDataView® ...................32
6. TROUBLESHOOTING ........................................................................ 33
6.1 ErrorMessages ......................................................................33
6.1.1 VoltagePresent ..........................................................33
6.1.2 Overrange ...................................................................34
6.1.3 NoisyMeasurement ....................................................34
6.1.4 Overheating ................................................................34
7. MAINTENANCE................................................................................ 35
7.1 Warning..................................................................................35
7.2 Cleaning ..................................................................................35
7.3 Charging/RechargingtheBattery ...........................................36
7.4 BatteryandFuseReplacement ..............................................37
RepairandCalibration ....................................................................38
TechnicalandSalesAssistance ......................................................38
Limited Warranty .............................................................................39
WarrantyRepairs ............................................................................39
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4 Micro-Ohmmeter Model 6240
CHAPTER 1
INTRODUCTION
WARNING
Thesesafetywarningsareprovidedtoensurethesafetyof
personnelandproperoperationoftheinstrument.
• Thisinstrumentisprotectedfromaccidentalvoltagesofnot
morethan50VwithrespecttoearthinmeasurementCat-
egoryIII.
• Donotattempttoperformanytestswiththisinstrumentuntil
youhavereadtheusermanual.
• Testsaretobecarriedoutonde-energizedcircuitsonly!
Never connect the unit to a live circuit.
• Makesurethatnoneoftheinputterminalsareconnected
andthattheswitchissettoOFFbeforepluggingintheAC
powertorechargethebatteryoftheinstrument.
• Makesuretheinternalbatteryisfullychargedpriortotesting.
Iftheinstrumenthasbeenleftunusedforseveralmonths,
rechargethebattery.
• Ifthecaseneedscleaning,donotuseanyalcoholoroil
basedcleaners.Preferablyusesoapywaterwithadamp
clothorsponge.Donotimmersethe6240micro-ohmmeter
inwater.
• Useconnectionaccessoriesofwhichtheovervoltagecat-
egoryandtheservicevoltagearegreaterthanorequalto
thoseofthemeasuringinstrument(50VCATIII).Useonly
accessoriesthatcomplywithsafetystandards(IEC61010-2-
031).
• Thetestleadsandmeasuringwiresmustbeingood
conditionandshouldbereplacedifthereisanyevidenceof
deterioration(insulationsplit,burnt,etc.).
•Troubleshootingandmetrologicalverification procedures
mustonlybeperformedbyqualified approvedpersonnel,or
thefactory.
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Micro-Ohmmeter Model 6240 5
1.1 International Electrical Symbols
Signifies that the instrument is protected by double or reinforced insulation.
This symbol on the instrument indicates a WARNING and that the operator must refer
to the user manual for instructions before operating the instrument. In this manual,
the symbol preceding instructions indicates that if the instructions are not followed,
bodily injury, installation/sample and/or product damage may result.
Risk of electric shock. The voltage at the parts marked with this symbol may
be dangerous.
When disposed of, this product must be sorted for the recycling of electrical
and electronic equipment in accordance with WEEE directive 2002/96/EC.
1.2 Definition of Measurement Categories
CAT II: Formeasurementsperformedoncircuitsdirectlyconnectedto
theelectricaldistributionsystem.Examplesaremeasurements
onhouseholdappliancesorportabletools.
CAT III:Formeasurementsperformedinthebuildinginstallationat
thedistributionlevelsuchasonhardwiredequipmentin
fixed installationandcircuitbreakers.
CAT IV: Formeasurementsperformedattheprimaryelectricalsupply
(<1000V)suchasonprimaryovercurrentprotectiondevices,
ripplecontrolunits,ormeters.
1.3 Receiving Your Shipment
Uponreceivingyour shipment,makesurethatthecontentsareconsistent
withthepackinglist.Notifyyourdistributorofanymissingitems.Ifthe
equipmentappearstobedamaged,file aclaimimmediatelywiththe
carrierandnotifyyourdistributoratonce,givingadetaileddescriptionof
anydamage.Savethedamagedpackingcontainertosubstantiateyour
claim.
NOTE: Charge the instrument fully before use.
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6 Micro-Ohmmeter Model 6240
1.4 Ordering Information
Micro-ohmmeter Model 6240 ............................................ Cat. #2129.80
Includes extra large tool bag, set of two 10ft Kelvin clips (10A - Hippo), set of two 10ft
Kelvin probes (1A - Spring Loaded), optical USB cable, US 115V power cord, two spare
fuses (12.5A), NiMH rechargeable battery pack, and USB stick supplied with product user
manual and DataView®software.
1.4.1 Accessories and Replacement Parts
Kelvinclips(10A-Hippo),10ftcolor-codedleads
withspadelugterminations ................................................. Cat. #1017.84
Kelvinclips(10A-Hippo),20ftcolor-codedleads
withspadelugterminations ................................................. Cat. #2118.70
KelvinProbes(1A-SpringLoaded),10ftwith4mmbanana
plugtermination(includessetof5forkterminals) ............... Cat. #2118.73
KelvinProbes(1A-SpringLoaded),20ftwith4mmbanana
plugtermination(includessetof5forkterminals) ............... Cat. #2118.74
KelvinProbesPistolGrip10ft(10A)SpringLoaded........... Cat. #2118.75
KelvinProbes10ft(10A)SpringLoaded ........................... Cat. #2118.77
KelvinClips10ft(1-10A) ..................................................... Cat. #2118.79
KelvinClips20ft(1-10A) ..................................................... Cat. #2118.80
Thermo-HygrometerModelCA846 .....................................Cat. #2121.24
OpticalUSBCable...............................................................Cat. #2135.41
ReplacementBattery6.5V,8.5AH ....................................... Cat. #2129.91
Fuse,setof5,12.5A/500V,6.3x32mm ............................. Cat. #2129.92
ExtraLargeClassicToolBag ..............................................Cat. #2133.73
Inverter–12VDCto120VAC200Wattforvehicleuse ......... Cat. #2135.43
115VPowerCordUS ..........................................................Cat. #5000.14
KelvinProbesPistolGrip20ft(10A)SpringLoaded........... Cat. #2118.76
KelvinProbes20ft(10A)SpringLoaded ........................... Cat. #2118.78
KelvinClips25ft(200A - Hippo) ......................................... Cat. #2129.72
KelvinClips50ft(200A - Hippo) ......................................... Cat. #2129.73
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Micro-Ohmmeter Model 6240 7
CHAPTER 2
PRODUCT FEATURES
2.1 Description
TheMicro-ohmmeterModel6240isusedtoperformlowresistance
measurementsfrom5μΩ to 400Ω.Therearesixrangeswithtestcurrents
from10mAto10A.
Thefrontendofthemicro-ohmmeteremploysafour-wireKelvinconfigu-
ration,whicheliminatestestleadresistanceforameasurementaccuracy
of0.25%.Abuilt-incircuitfilters outACsignals.
TheMicro-ohmmeterModel6240ispackagedinasealedfield casewell
suitedforshopandfield use.Powerissuppliedbyalong-lifeNiMH
batterypackwithabuilt-inrecharger(110/220V).
Thelarge,easy-to-readliquidcrystaldisplayis2.25x4.00".Itdisplaysthe
valueofresistance,currentorvoltagetest,polarityandbatterycharge.
Foroperatorsafetyandinstrumentprotection,themicro-ohmmeterisfuse
protectedattheinputs.Onefuse,accessiblefromthefrontpanel,protects
againststoredenergyininductiveloads.
Enhancedinternalcircuitryprotectsagainstpossibleinductivekick-
backwhenthecurrentisshutoff.
Abuilt-inthermalswitchprotectsthemicro-ohmmeteragainstoverheating
onthe10Arangewhenincontinuoususe.
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8 Micro-Ohmmeter Model 6240
2.2 Applications
Someofthemorepopularandmostfrequentusesofthemicro-ohmmeter
areinapplicationsfor:
• Checkingmetalliccoatingresistance,especiallyinaeronautics
• Groundconnectionsandcontinuitymeasurement
• Resistancemeasurementsonmotorsandsmalltransformers
• Contactresistancemeasurementsonbreakersandswitches
• Componentmeasurement
• Electricalcableresistancemeasurement
• Mechanicalbondtests
• Wire to terminal connections
• Aircraftandrailbonds
2.3 Key Features
• Measuresfrom5µΩ to 400Ω
• Testcurrentselectionfrom10mAto10A
• Manualtemperaturecompensation(withDataView®software)
• Frontpanelpolarityreversefunction
• Storesupto99testresults
• Operatorsafetybyautomaticdischargeofresidualchargeonthe
equipmentundertest
• Instantaneous,continuousormultipletestoperation
• Autostoreofmultipletestresults
• Internal,rechargeablebatteriesconductupto850,10Atests
• Abuilt-inbatterypackrechargerrechargesthebatteriesby
connectingtotheACline(110V-230V,50/60Hz)usingastandard
line cord
• 4-Wiremeasurementwithautomaticcompensationof
undesirablevoltagesandleadresistance
• Largemulti-functionbacklitdisplay
• Directdisplayofthemeasurementwithunits,rangeandtest
current
• Rugged,sealedcase
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Micro-Ohmmeter Model 6240 9
2.4 Control Features
°C°F
mV
mA
°
>
<
V
µmΩ
AVG
OBJ. TEST
MEMMRCLR
P
HOLD
COM
DC
AC
2nd
I
+I
_
1
7
8
6
4
235
Figure 2-1
1. Kelvininputterminals
2. AClinerechargingreceptacle
3. Outputfuse-12.5A,500V,6x32mm
4. Largemulti-linebacklitliquidcrystaldisplay(see§2.6)
5. Opticalinterfaceconnectorforconnectiontoacomputer
6. Rangeselectionswitch
7. Start/Stopbutton
8. Program/functionbuttons(see§2.5)
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10 Micro-Ohmmeter Model 6240
2.5 Button Functions
MEM Stores the measurement at an address identified by an object number
(OBJ) and a test number (TEST).
Two presses on this button are required, one to select the location (use
the▲and►buttons to change the location) and another to store the
measurement.
MR Retrieves stored data except for the OFF and SET-UP positions (this
function is independent of the selector setting of the switch). Data is
viewed using the▲and►buttons.
± I Reverses the direction of the current and displays the average.
DISPLAY Displays the current or voltage on the terminals.
AUTO>2s
Activates automatic recordings.
Used in the SET-UP and memory mode, selects a function or incre-
ments a flashing parameter.
Used in the SET-UP and memory mode, accesses the function to be
modified.
CLR Erases the memory
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Micro-Ohmmeter Model 6240 11
2.6 Display Symbols
Thedisplayincorporatestwolinesofcharacterstodisplaytestresults,as
wellasalibraryofsymbolstoassisttheoperatorindeterminingconditions
ataglance.ThesymbolsthatcanappearareshowninFigure2-2.
°C°F
mV
mA
°
>
<
V
µmΩ
AVG
OBJ. TEST
MEMMRCLR
P
HOLD
COM
DC
AC
2nd
I
+I
_
Figure 2-2
Indicates the measurement is noisy; accuracy is not guaranteed
Indicates the battery charge condition; the segments represent energy
Indicates that power down is deactivated
Not used
MEM Displayed measurement about to be stored in memory
MR Memory recall
CLR
Indicates the memory is being erased
Indicates internal overheating
+ I Indicates the direction of current
- I Indicates the direction of current
Indicates that a measurement has been stopped
OBJ. First position locator for data stored in memory
TEST Second position locator for data stored in memory
°C / °F Not used
Memory utilization indicator
AVG Displays average
Not used
>Indicates an overrange
R(+I)+R(-I)
2
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12 Micro-Ohmmeter Model 6240
CHAPTER 3
SPECIFICATIONS
3.1 Electrical
Specications are given for an ambient temperature of 23°C ± 3°C, rela-
tive humidity of 45 to 55%, supply voltage of 6V ± 0.2V and magnetic eld
of <40A/m.
RESISTANCE
Measurement
Range
5.0 to
3999µΩ
4.0 to
39.99mΩ
40.0 to
399.9mΩ
400 to
3999mΩ
4.0 to
39.99Ω
40.0 to
399.9Ω
Resolution 1µΩ10µΩ100µΩ1mΩ10mΩ100mΩ
Accuracy ± 0.25% ± 2ct
Measurement
current
10.2A
± 2% (1)
1.02A
± 2%
102mA
± 2%
10.2mA
± 2% (2)
Open voltage 4 to 6V
Inductance 0.5H Max
(1) With nominal value of 10.2A, the measurement current is at least 10A whatever the charge condition of the battery.
(2) The current is 10mA only up to 300Ω. If the battery is low, it can fall to as low as 8mA.
VOLTAGE MEASUREMENT INDICATION
Measurement
Range
0.01 to
3.999mV
4.0 to
39.99mV
40.0 to
399.9mV
0.40 to
3.999V
4.0 to
4.70V
Resolution 1µV 10µV 100µV 1mV 10mV
CURRENT MEASUREMENT INDICATION
Measurement
Range
5.0 to
39.99mA
40.0 to
399.9mA
0.40 to
3.999A
4.0 to
11.00A
Resolution 10µA 100µA 1mA 10mA
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Micro-Ohmmeter Model 6240 13
Inuences on the Resistance Measurement
Quantities of Influence Range of use Variation of the measurement
Typical Maximum
Temperature -10 to +55°C 0.1% /10°C 0.5% /10 °C + 2cts
Relative Humidity 10 to 85% RH @ 45°C 0.1 % 0.5% + 2cts
Supply Voltage 5 to 7V 2cts 0.2% / V + 2cts
Series Mode Rejection,
50/60Hz*
U (AC) = (R measured x
I measurement) < 0.2% 2% + 1ct
Common Mode
Rejection, 50/60Hz AC 0 to 50 V AC > 80 dB > 60 dB
*Example: If the measured resistance is 1mΩand the measurement current is 10A, an alternating voltage of 1mV RMS
in series with the resistance to be measured will induce an error of not more than 2%.
Power Supply:6V,8.5AhrechargeableNiMHbatterypack
Battery Life: Rangedependent
Range Number of measurements*
10A 850
1A 3500
100mA 4500
10mA 5000
In Standby or Off battery life 4 to 6 months
*Established for measurements lasting 5s, every 25s.
3.2 Mechanical
Dimensions:
10.70x9.76x7.17"(272x248x182mm)
Weight:
10lbs(4.5kgapprox)
Case Protection:
ABSplasticpolycarbonate:watertighttoIP64
(coverclosed),waterresistanttoIP53(coveropen).
Color:
Safetyyellowcasewithgrayfaceplate
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14 Micro-Ohmmeter Model 6240
3.3 Environmental
Operating Temperature:
14°to132°F(-10°to55°C),10to85%RH
Storage Temperature:
-40°to158°F(-40°to70°C);10to90%RH
Altitude:<2000m
NOTE: For long-term storage (>1 year) with the battery installed, the stor-
age range is -4 to 86°F (-20 to 30°C); 85% RH, otherwise the battery will
deteriorate. For short-term storage (1 month) the temperature can reach
up to 122°F (50°C).
3.4 Safety
ElectricalsafetyasperEN61010-1(Ed.2of2001),EN61557(Ed.97)
parts1and4.
Degreeofpollution:2
Protection:MeasurementCATIII,50Vwithrespecttoearth,500V
differentialbetweenterminals,and300VCATIIonthechargerinput
Electromagnetic Compatibility:
Theinstrumentsatisfies theCEMandDBTdirectivesrequiredfortheCE
markingandproductstandardEN61326-1(Ed.97)+A1(Ed.98)
Emissions in residential environment
Immunityinindustrialenvironment
*Specications are subject to change without notice
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Micro-Ohmmeter Model 6240 15
CHAPTER 4
OPERATION
NOTE: Charge the instrument fully before use.
4.1 Precautions Before Use
•Never usetestleadsormeasuringwiresifthereisanyevidenceof
deterioration(insulationsplit,burnt,etc).
•Never exceedthesafetyvaluesindicatedinthespecifications
•Never connecttheunittoalivecircuit.
•
Never disconnecttheconnectionwiresbeforethe icondisappears
fromthedisplay.
4.2 Instrument Configuration (SET-UP mode)
TheSET-UPmodeisusedtomodifytheinstrument’sconfiguration. This
canalsobeperformedbyusingtheDataView®softwarethatcamewith
theinstrument(see§5).
Toconfigure theModel6240directlyfromthedisplay,turntherotary
switchtotheSET-UPposition.Thefollowingscreenwillappear:
MEM
• The display order of the parameters that can be modied is:
- Clear all memory (see§4.9.2)
- Time
- Date
- AutomaticPowerO󰀨
- DisplayoftheInternalParameters(e.g.serialnumber,software
version,dateoflastcalibration,lightingofallsegmentsondisplay)
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16 Micro-Ohmmeter Model 6240
To display and modify parameters:
•Tomovethroughparameters,pressthe button.
•Tochangethedisplayedparametersorviewadditionalones,press
andholdthebutton.
•Tomodifytheparameters,usethebutton.
•Toacceptthechanges,pressandholdthe button>2suntilthe
displaystopsblinking.
4.3 Resistance Measurements
WARNING: Before performing the resistance test, verify that the sample
under test is not energized.
1. Cleanallsurfacesbeforeconnectingtestleads.
2. Connectthetwoleadstothefourterminals,thenthetwoKelvinclips
totheobjecttobetested.
3. Settherangeselectorswitchtothedesiredrangeforthetest.Ifthe
anticipatedresistanceisnotknown,beginwiththehighestrange
(400Ω)andsuccessivelylowertherangeselectionuntiladequate
resolutionisachieved.
4. PresstheSTART/STOPbuttontostartthemeasurement.
NOTE: The START/STOP needs to be pressed each time the range is
changed. The range selection may be changed while the instrument is on.
HOLD
5. PresstheSTART/STOPbuttonagaintostopthemeasurementor
disconnectoneoftheKelvinclips.Thelastmeasurementmadeis
displayedalongwiththe symbol.
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Micro-Ohmmeter Model 6240 17
NOTE: If the measurement was stopped by disconnecting a Kelvin clip,
simply connect it to another object to start the next measurement; it is
not necessary to press the START/STOP button.
6. Todisplaythevoltageontheterminalsoftheresistanceinsteadofthe
measurementcurrent,presstheDISPLAYkey.
Current results are displayed
before pressing DISPLAY button
Voltage results are displayed
after pressing DISPLAY button
4.3.1 Measurement Readings
Whentestingresistivesamples,themeterreadingwillstabilizewithinthe
first fewhundredmilliseconds.Oninductiveloads(e.g.smalltransform-
ers),themeasurementreadingmaytakefromseveralsecondstoafew
minutestostabilizeanddependsgreatlyonthetypeofequipmentandthe
impedanceoftheequipmentundertest.
4.3.2 Connections and Readings
TheModel6240generatesacurrent(I)
fromtheinternalvoltagesource(V).A
voltmetermeasuresthevoltagedrop
VxattheKelvinprobecontactpointsto
theresistancetobemeasured(Rx)and
displaystheresistancemeasurement
(Rx)directlyusingtheformulaRx=Vx/I.
Theresultisnotaffected bytheother
resistancesencounteredinthecurrent
loop(Ri,Rf,Rc),aslongasthetotal
voltagedropinducedacrossRx remains
belowthevoltagesuppliedbythesource
whichisbetween5to6V.Themaximum
admissible lead resistance level is Rf≈(V-Vx)/I.TheuseofKelvin
probeshelps,astheyeliminatetheeffect oftheleadresistance(Rf).
Ri Rf
Rf
Rf
Rf
C2
P2
P2
C1
Rc
Rx
Rc
V
I
Vx
+
Ri=Unitinternalresistance
Rf = Lead resistance
Rc = Contact resistance
Rx=Resistancetobemeasured
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18 Micro-Ohmmeter Model 6240
4.3.3 Test Lead Connection
Themeasurementleadsareconnectedusingthefourbindingpostsonthe
leftsideofthefrontpanelasshownbelow.
ConnectthetworedleadstoterminalsC1andP1.Connectthetwoblack
leadstoterminalsC2andP2.
Anydropinthevoltageontheloadterminalsismeasuredbetweenthetwo
“voltage”(V)leads,P1andP2.Thecurrentleads(C1andC2)candeliver
currentfrom10mAto10A.
UI
4.4 Repetitive Measurements
1. ConnecttheKelvinclipstothefirst object.PressSTART/STOP.
2. Disconnecttheclips.Themeasurementstopsandresultisdisplayed.
3. Connecttheclipstothesecondobject.Themeasurementrestarts
automatically.Repeatasnecessary.
4. Afterthelastmeasurement,pressSTART/STOPagain.
NOTE: This operation is valid only if all of the objects to be measured have
substantially the same value and all of the measurements are made in the
same range.
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Micro-Ohmmeter Model 6240 19
4.5 Measuring Very Low Resistance
WhenmeasuringverylowresistivevaluesintheµΩrange,thepresence
ofstrayDCcurrentsmayaffect theaccuracyofthemeasurements.
Thesecurrentscanbepresentduetoavarietyofreasonsincluding
chemicalorthermalEMFinsamplesmadeofdissimilarmetals.
Youcaneliminatetheeffects ofthisbyreversingthedirectionofcurrent
flow (seeexamplebelow)andusingtheaverageofforwardandreverse
readings.
ThepresenceofACinterferenceinthesampleundertestmaycausethe
measuredvalueonthedisplaytofluctuate. Thisinterferencemay
becomemorenoticeableinthepresenceofstrongelectricfields. The
effectofthisinterferencemaybereducedbytwistingtheleadsaround
eachother.
1. Reversethedirectionofthecurrentbypressingthe±Ibuttonandthe
instrumentdisplaystheaverage:
R(+I)+R(-I)
RAVG = 2
2. TodisplaythevaluesR(+I)andR(-I),presstheDISPLAYbutton.
A
µ Ω
AVG
HOLD
I
_
+I
R(+I)
+V
R(+I)
-I
R(-I)
-V
R(-I)
Press the DISPLAY button to cycle through the values
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