微电阻四线量测法

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1、除了在第3.2节介绍的所有低电压测量中要考虑的问题之外，在低电阻的测量中更容易引进附加的误差源，其中包括引线电阻、非欧姆接触以及器件的加热问题。这一节将要介绍这些误差源以及将其消除或者降至最小的各种方法。此外还要介绍其它一些测量中要考虑的因素，包括干电路测试和电感性器件的测试等。3.3.1LeadResistanceandFour-WireMethod引线电阻和四线方法Resistancemeasurementsareoftenmadeusingthetwo-wiremethodshowninFigure3-14.Thetestcur

2、rentisforcedthroughthetestleadsandtheresistance(R)beingmeasured.Themeterthenmeasuresthevoltageacrosstheresistancethroughthesamesetoftestleadsandcomputestheresistancevalueaccordingly.电阻的测量常常使用图3-14所示的两线方法来进行。我们迫使测试电流流过测试引线和被测电阻（R）。然后仪表通过同一套测试引线来测量电阻两端的电压，并计算出相应的电阻数值。Them

3、ainproblemwiththetwo-wiremethodasappliedtolowresistancemeasurementsisthatthetotalleadresistance(RLEAD)isaddedtothemeasurement.Sincethetestcurrent(I)causesasmallbutsignificantvoltagedropacrosstheleadresistances,thevoltage(VM)measuredbythemeterwon’tbeexactlythesameasthevo

4、ltage(VR)directlyacrossthetestresistance(R),andconsiderableerrorcanresult.Typicalleadresistanceslieintherangeof1m.to10mΩ,soit’sverydifficulttoobtainaccuratetwo-wireresistancemeasurementswhentheresistanceundertestislowerthan10.to100.(dependingonleadresistance).两线测量方法用于低阻

5、测试时的主要问题是测量结果中增加了引线的总电阻（RLEAD）。由于测试电流（I）在引线电阻上产生了一个小的、但是很重要的电压降，所以仪表测量的电压（VM）就不会和被测电阻（R）上的电压完全相同，于是产生了相当的误差。典型的引线电阻在1mΩ到10mΩ的范围内，所以当被测电阻小于10Ω到100Ω时，就很难用两线测量方法来获得准确的测量结果（取决于引线电阻的数值）。Duetothelimitationsofthetwo-wiremethod,thefour-wire(Kelvin)connectionmethodshowninFigure3

6、-15isgenerallypreferredforlowresistancemeasurements.ThesemeasurementscanbemadeusingaDMM,micro-ohmmeter,oraseparatecurrentsourceandvoltmeter.Withthisconfiguration,thetestcurrent(I)isforcedthroughthetestresistance(R)throughonesetoftestleads,whilethevoltage(VM)acrosstheDUT

7、ismeasuredthroughasecondsetofleadscalledsenseleads.Althoughsomesmallcurrentmayflowthroughthesenseleads,itisusuallynegligibleandcangenerallybeignoredforallpracticalpurposes.Thevoltagedropacrossthesenseleadsisnegligible,sothevoltagemeasuredbythemeter(VM)isessentiallythesa

8、measthevoltage(VR)acrosstheresistance(R).Consequently,theresistancevaluecanbedeterminedmuchmoreaccuratelythanw