Voltage and Temperature Measurements
2-23
Applications
Low-resistance measurements
The Model 2182 can be used with a current source to measure resistances at levels well below
the capabilities of most conventional instruments. The following paragraphs discuss low-
resistance measurement techniques and include some applications to test switches.
Measurement techniques
Techniques used to measure resistances in the normal range are not generally suitable for
making low-resistance measurements because of errors caused by voltage drops across the test
leads. To overcome these limitations, low resistance measurements are usually made using the
4-wire (Kelvin) connections shown in
. A current source forces the current (I)
through an unknown resistance, developing a voltage across that device. Even though the test
lead resistance, R
LEAD
, is present, it does not affect the current through R
DUT
because I is
assumed to be a constant current source with high output impedance. Also, since the voltmeter
has a very high input resistance (very low leakage current), the current through the sense leads
will be negligible, and the voltage drop across R
LEAD
will be essentially zero. Thus, the voltage
measured by the meter will be essentially the same as the voltage across the unknown resistance,
R
DUT
.
Figure 2-10
4-Wire low-resistance measurement technique
Since the current through the measured resistance and the voltage across the device are both
known, the value of that resistance can easily be determined from Ohm's law:
R
DUT
= V
M
/I
R
LEAD
R
LEAD
I
V
OFFSET
R
DUT
V
M
Voltmeter
R
LEAD
R
LEAD
R
DUT
=
V
M
I
Current
Source
Содержание 2182
Страница 1: ...www tek com keithley Model 2182 2182A Nanovoltmeter User s Manual 2182A 900 01 Rev B May 2017...
Страница 18: ......
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Страница 23: ...1 Getting Started Getting Started...
Страница 41: ...2 VoltageandTemperature Measurements Voltageand Temperature Measurements...
Страница 68: ...2 28 Voltage and Temperature Measurements...
Страница 69: ...3 Range Digits Rate andFilter Range Digits Rate andFilter...
Страница 82: ...3 14 Range Digits Rate and Filter...
Страница 83: ...4 Relative mX b and Percent Relative mX b andPercent...
Страница 91: ...5 RatioandDelta Ratioand Delta...
Страница 117: ...6 Buffer Buffer...
Страница 123: ...7 Triggering Triggering...
Страница 140: ...7 18 Triggering...
Страница 141: ...8 Limits Limits...
Страница 149: ...9 SteppingandScanning Steppingand Scanning...
Страница 168: ...9 20 Stepping and Scanning...
Страница 169: ...10 AnalogOutput Analog Output...
Страница 175: ...11 RemoteOperation Remote Operation...
Страница 205: ...12 CommonCommands Common Commands...
Страница 221: ...13 SCPISignalOriented Measurement Commands SCPISignalOri entedMeasure ment Commands...
Страница 225: ...14 SCPIReferenceTables SCPIRefer enceTables...
Страница 239: ...15 AdditionalSCPI Commands Additional SCPICom mands...
Страница 260: ...15 22 Additional SCPI Commands...
Страница 261: ...A Specifications Specifications...
Страница 263: ...B Statusand ErrorMessages StatusandError Messages...
Страница 268: ...B 6 Status and Error Messages...
Страница 269: ...C Measurement Considerations Measurement Consider ations...
Страница 278: ...C 10 Measurement Considerations...
Страница 279: ...D Model182Emulation Commands Model182 EmulationCom mands...
Страница 284: ...D 6 Model 182 Emulation Commands...
Страница 285: ...E Example Programs ExamplePro grams...
Страница 293: ...F IEEE 488 BusOverview IEEE 488Bus Overview...
Страница 307: ...G IEEE 488andSCPI ConformanceInformation IEEE 488and SCPIConform anceInforma tion...
Страница 310: ...G 4 IEEE 488 and SCPI Conformance Information...
Страница 311: ...H Measurement Queries Measurement Queries...
Страница 316: ...H 6 Measurement Queries...
Страница 317: ...I Delta PulseDelta and DifferentialConductance Delta Pulse Deltaand Dif ferentialCon ductance...