用开尔文双电桥测低电阻.docx
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用开尔文双电桥测低电阻.docx
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用开尔文双电桥测低电阻
用开尔文双电桥测低电阻
实验,,用开尔文双电桥测低电阻
-3单电桥桥臂上的导线电阻和接点处的接触电阻约为10Ω量级。
由于这些附加电阻与桥臂电阻相比小得多,故可忽略其影响。
但若用它测,Ω以下的电阻时,这些附加电阻对测量结果的影响就突出了。
开尔文双电桥可用于测量-610Ω,,,Ω的电阻,有效地消减了附加电阻的影响。
【预习重点】
(,)四端电阻的电流端和电压端的含义及其在电路中避免附加电阻影响的原理。
(,)双电桥测低电阻的原理和方法。
atmosphericpressurevessel4GB50231-2009mechanicalequipmentinstallationengineeringconstructionandacceptancespecificationfor5GB50275-98compressor,fanandpumpinstallationengineeringconstructionandacceptancespecificationforlifting6HG20201-2000constructioninstallationengineeringconstructionstandard7,HG...Pressuregauges,usinganinstalledsparkarrestorforacetylenecylinders,illegalcarrying,usinggascylinders,eachoperatorfined20Yuan.Gasbottlewithoutthehotsunexposuremeasures,responsibilitiesofteamafineof50Yuan.(7)atheightandtheopeningandprovisionalprotectivemeasureshavebeentaken,theresponsibleunitfined200Yuan,constructionpersoninchargeafineof50Yuan.(8)nopermittoworkandthejobinaccordancewiththeprovisions,onthejobunitfined300yuan,theunitwillchargeafineof100Yuan.7.5.3accidentpenalties
(1)injuriesfatalitiesdirectlypunished1~2million.Directresponsibilityfortheaccidentandhavethecorrespondingresponsibilityofleadership,suchasconcerningadministrativesanctions,shouldbebroughttothecompanyortherelevantDepartment.
(2)personalinjuryaccidentoccurred,thedirectpunishment0.5-10,000yuan,responsibleforthedirectresponsibilityfortheaccidentandtheresponsibilityofleadership,suchasconcerningadministrativesanctionsshouldbedealtwithbythepersonnelDepartmentofthecompany.(3)personalinjuryaccidentoccurs,thedirectpunishment500-1000,whoisdirectlyresponsiblefortheaccidentresponsibility,givenoticeofcriticismand50-100economicsanctionsagainstthem.(4)toconcealtheaccident,reportedwithoutunduedelayorfalse,toinformtheadministrativeleadershipofthecriticism,resultinginseriousconsequences,thepursuit
(,),,,,,,型直流复射式检流计的使用(参阅本实验附录)。
【仪器】
开尔文双电桥、直流稳定电源(该电源为稳压稳流电源,实验时按稳流源使用)、检流计、标准电阻、待测电阻等。
【原理】
)双电桥线路结构及消减附加电阻影响的原理
图,,—,(,)、(,)为双电桥线路结构及其等效电路。
双电桥在线路结构上与单电桥有两点显著不同:
?
待测电阻,和桥臂电阻,(标准电阻)均xN
为四端接法;?
增加两个高阻值电阻,、,,构成双电桥的“内臂”。
34
图,,—,双电桥及其等效电路
四端电阻外侧的两个接点称为电流端,通常接电源回路,从而将电流端的附加电阻折合到电源回路的电阻中。
图,,—,中,,、,两接点的附加电阻折11
入了电源内阻。
、,两接点用短粗导线相连,设,、,间附加电阻为,。
后1313
面将证明,若,、,、,、,及,满足一定条件,即可消减,对测量结果的影1234N
响。
atmosphericpressurevessel4GB50231-2009mechanicalequipmentinstallationengineeringconstructionandacceptancespecificationfor5GB50275-98compressor,fanandpumpinstallationengineeringconstructionandacceptancespecificationforlifting6HG20201-2000constructioninstallationengineeringconstructionstandard7,HG...Pressuregauges,usinganinstalledsparkarrestorforacetylenecylinders,illegalcarrying,usinggascylinders,eachoperatorfined20Yuan.Gasbottlewithoutthehotsunexposuremeasures,responsibilitiesofteamafineof50Yuan.(7)atheightandtheopeningandprovisionalprotectivemeasureshavebeentaken,theresponsibleunitfined200Yuan,constructionpersoninchargeafineof50Yuan.(8)nopermittoworkandthejobinaccordancewiththeprovisions,onthejobunitfined300yuan,theunitwillchargeafineof100Yuan.7.5.3accidentpenalties
(1)injuriesfatalitiesdirectlypunished1~2million.Directresponsibilityfortheaccidentandhavethecorrespondingresponsibilityofleadership,suchasconcerningadministrativesanctions,shouldbebroughttothecompanyortherelevantDepartment.
(2)personalinjuryaccidentoccurred,thedirectpunishment0.5-10,000yuan,responsibleforthedirectresponsibilityfortheaccidentandtheresponsibilityofleadership,suchasconcerningadministrativesanctionsshouldbedealtwithbythepersonnelDepartmentofthecompany.(3)personalinjuryaccidentoccurs,thedirectpunishment500-1000,whoisdirectlyresponsiblefortheaccidentresponsibility,givenoticeofcriticismand50-100economicsanctionsagainstthem.(4)toconcealtheaccident,reportedwithoutunduedelayorfalse,toinformtheadministrativeleadershipofthecriticism,resultinginseriousconsequences,thepursuit
四端电阻内侧的两个接点称为电压端,通常接高电阻回路或电流为零的补偿回路。
图,,—,中,,、,端接触电阻分别并入,、,;,、,端接触电221224阻分别并入,、,。
由于,、,、,、,本身电阻很高,所以这些附加电阻对341234
它们的影响甚微。
此外,电压端之间的部分即为低电阻本身,无另外的连接导线,故有效地消除了导线电阻的影响。
)双电桥的平衡条件
调节平衡,就是调节电阻,、,、,、,和,,使,、,两处等电位,检1234N
流计电流,,,。
由图,,—,(,)中所示电流方向,考虑到,>>,,,>>g112,,,>>,,,>>,,可列出方程23344
联立求解得
(,,—,)
双电桥在结构上尽量做到使上式第二项满足,故
(,,—,)
式(,,—,)就是双电桥的平衡条件。
只要待测低电阻按四端接法接入测量,就可像单电桥那样用式(,,—,)计算,了。
x
),,,,型直流单、双电桥的结构及使用
atmosphericpressurevessel4GB50231-2009mechanicalequipmentinstallationengineeringconstructionandacceptancespecificationfor5GB50275-98compressor,fanandpumpinstallationengineeringconstructionandacceptancespecificationforlifting6HG20201-2000constructioninstallationengineeringconstructionstandard7,HG...Pressuregauges,usinganinstalledsparkarrestorforacetylenecylinders,illegalcarrying,usinggascylinders,eachoperatorfined20Yuan.Gasbottlewithoutthehotsunexposuremeasures,responsibilitiesofteamafineof50Yuan.(7)atheightandtheopeningandprovisionalprotectivemeasureshavebeentaken,theresponsibleunitfined200Yuan,constructionpersoninchargeafineof50Yuan.(8)nopermittoworkandthejobinaccordancewiththeprovisions,onthejobunitfined300yuan,theunitwillchargeafineof100Yuan.7.5.3accidentpenalties
(1)injuriesfatalitiesdirectlypunished1~2million.Directresponsibilityfortheaccidentandhavethecorrespondingresponsibilityofleadership,suchasconcerningadministrativesanctions,shouldbebroughttothecompanyortherelevantDepartment.
(2)personalinjuryaccidentoccurred,thedirectpunishment0.5-10,000yuan,responsibleforthedirectresponsibilityfortheaccidentandtheresponsibilityofleadership,suchasconcerningadministrativesanctionsshouldbedealtwithbythepersonnelDepartmentofthecompany.(3)personalinjuryaccidentoccurs,thedirectpunishment500-1000,whoisdirectlyresponsiblefortheaccidentresponsibility,givenoticeofcriticismand50-100economicsanctionsagainstthem.(4)toconcealtheaccident,reportedwithoutunduedelayorfalse,toinformtheadministrativeleadershipofthecriticism,resultinginseriousconsequences,thepursuit
图,,—,,,,,型电桥电路
双电桥形式、结构及使用虽多种多样,但其原理是一样的。
图,,—,和,
—,分别为,,,,型单双电桥的线路及其作为双电桥使用时的面板接线图。
-526电桥等级:
.,,;量程:
双桥为10Ω,10Ω,单桥为,,Ω,10Ω;保证
-35准确度等级的测量范围:
10Ω,10Ω。
外接标准电阻,,,.,,Ω和,,,.NN
,,Ω,,.,,级。
示零器为外接,,,,,,型检流计。
atmosphericpressurevessel4GB50231-2009mechanicalequipmentinstallationengineeringconstructionandacceptancespecificationfor5GB50275-98compressor,fanandpumpinstallationengineeringconstructionandacceptancespecificationforlifting6HG20201-2000constructioninstallationengineeringconstructionstandard7,HG...Pressuregauges,usinganinstalledsparkarrestorforacetylenecylinders,illegalcarrying,usinggascylinders,eachoperatorfined20Yuan.Gasbottlewithoutthehotsunexposuremeasures,responsibilitiesofteamafineof50Yuan.(7)atheightandtheopeningandprovisionalprotectivemeasureshavebeentaken,theresponsibleunitfined200Yuan,constructionpersoninchargeafineof50Yuan.(8)nopermittoworkandthejobinaccordancewiththeprovisions,onthejobunitfined300yuan,theunitwillchargeafineof100Yuan.7.5.3accidentpenalties
(1)injuriesfatalitiesdirectlypunished1~2million.Directresponsibilityfortheaccidentandhavethecorrespondingresponsibilityofleadership,suchasconcerningadministrativesanctions,shouldbebroughttothecompanyortherelevantDepartment.
(2)personalinjuryaccidentoccurred,thedirectpunishment0.5-10,000yuan,responsibleforthedirectresponsibilityfortheaccidentandtheresponsibilityofleadership,suchasconcerningadministrativesanctionsshouldbedealtwithbythepersonnelDepartmentofthecompany.(3)personalinjuryaccidentoccurs,thedirectpunishment500-1000,whoisdirectlyresponsiblefortheaccidentresponsibility,givenoticeofcriticismand50-100economicsanctionsagainstthem.(4)toconcealtheaccident,reportedwithoutunduedelayorfalse,toinformtheadministrativeleadershipofthecriticism,resultinginseriousconsequences,thepursuit
图,,—,双电桥面板接线
图,,—,中可变电阻,、,采用同轴调节的两个相同的,位(×,.,,、13
×,.,、×,、×,,、×,,,)十进电阻箱,这样无论转盘位于何处,都
234能保证,,,。
、,是两个可独立调节的,,进,挡(10、10、10、10Ω)1324
电阻箱,调节,,,,从而保证在使用过程中始终成立。
24
使用时应首先根据,的粗估值设定,、,的初值。
将式(,,—,)改写x12
为,可知相当于单电桥的倍率,,相当于测量盘的示值。
与1单电桥一样,根据,的数量级选定的,应保证,的,个旋钮都用上(即保x1
证,位有效数字)。
,,,型电桥作为双电桥使用时,其示值误差限atmosphericpressurevessel4GB50231-2009mechanicalequipmentinstallationengineeringconstructionandacceptancespecificationfor5GB50275-98compressor,fanandpumpinstallationengineeringconstructionandacceptancespecificationforlifting6HG20201-2000constructioninstallationengineeringconstructionstandard7,HG...Pressuregauges,usinganinstalledsparkarrestorforacetylenecylinders,illegalcarrying,usinggascylinders,eachoperatorfined20Yuan.Gasbottlewithoutthehotsunexposuremeasures,responsibilitiesofteamafineof50Yuan.(7)atheightandtheopeningandprovisionalprotectivemeasureshavebeentaken,theresponsibleunitfined200Yuan,constructionpersoninchargeafineof50Yuan.(8)nopermittoworkandthejobinaccordancewiththeprovisions,onthejobunitfined300yuan,theunitwillchargeafineof100Yuan.7.5.3accidentpenalties
(1)injuriesfatalitiesdirectlypunished1~2million.Directresponsibilityfortheaccidentandhavethecorrespondingresponsibilityofleadership,suchasconcerningadministrativ
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