Ratio and Delta
5-19
For even greater precision, the Relative feature of the Model 2182 can be used to null out
thermal EMFs, which can corrupt low voltage measurements. Use Rel as follows:
1.
While displaying the Ratio result, disconnect the current source from the network.
2.
Press the REL key on the Model 2182. The voltages at each input, which are thermal
EMFs, are nulled out.
3.
Reconnect the current source and take the result of Ratio from the display.
When using Rel, Ratio is calculated as follows:
Filt V1-V1 Rel
Ratio =
Filt V2-V2 Rel
The above calculation includes Channel 1 Filter. If Filter is not
used, remove the “Filt” component from the calculation.
Testing superconductor materials
A superconductor sample is typically tested by either varying the current through it or varying
the magnetic field that surrounds it.
NOTE
The following applications use H (magnetic field) as one of the test parameters. The
applications can easily be modified to substitute temperature (T) for H as a test
parameter.
When varying the magnetic field (H), the current (I) that flows through the DUT is fixed.
When varying the current (I) through the superconductor material (DUT), the magnetic field (H)
that surrounds it is held constant.
For the following two applications, the Model 2182 is used to measure voltage and a Keithley
SourceMeter (Model 2400, 2410, or 2420) is used to source a known current(s). Therefore,
whether varying the magnetic field or varying the current, the actual resistance of the DUT can
be calculated using Ohm’s Law: R = V/I.
Thermal EMFs
— Test leads that connect the Model 2182 to the superconductor sample
(DUT) in a cryostat are typically 30 feet or longer. The test lead connections, and the wide
temperature range (from ~0K at the DUT to the ambient temperature of the lab) create
substantial thermal EMFs in the test leads. The effects of these thermal EMFs must be canceled
to achieve accurate voltage measurements.
To cancel the effects of thermal EMFs, the DC current-reversal measurement technique must
be used. This measurement technique requires a source that can provide a bipolar output. When
using a SourceMeter, a custom sweep can be configured to provide a bipolar output.
By enabling Delta measurements on the Model 2182, the effects of thermal EMFs in the test
leads will automatically be canceled during the source-measure process. For details on the DC
current-reversal technique, see “
Summary of Contents for 2182
Page 1: ...www tek com keithley Model 2182 2182A Nanovoltmeter User s Manual 2182A 900 01 Rev B May 2017...
Page 18: ......
Page 22: ......
Page 23: ...1 Getting Started Getting Started...
Page 41: ...2 VoltageandTemperature Measurements Voltageand Temperature Measurements...
Page 68: ...2 28 Voltage and Temperature Measurements...
Page 69: ...3 Range Digits Rate andFilter Range Digits Rate andFilter...
Page 82: ...3 14 Range Digits Rate and Filter...
Page 83: ...4 Relative mX b and Percent Relative mX b andPercent...
Page 91: ...5 RatioandDelta Ratioand Delta...
Page 117: ...6 Buffer Buffer...
Page 123: ...7 Triggering Triggering...
Page 140: ...7 18 Triggering...
Page 141: ...8 Limits Limits...
Page 149: ...9 SteppingandScanning Steppingand Scanning...
Page 168: ...9 20 Stepping and Scanning...
Page 169: ...10 AnalogOutput Analog Output...
Page 175: ...11 RemoteOperation Remote Operation...
Page 205: ...12 CommonCommands Common Commands...
Page 221: ...13 SCPISignalOriented Measurement Commands SCPISignalOri entedMeasure ment Commands...
Page 225: ...14 SCPIReferenceTables SCPIRefer enceTables...
Page 239: ...15 AdditionalSCPI Commands Additional SCPICom mands...
Page 260: ...15 22 Additional SCPI Commands...
Page 261: ...A Specifications Specifications...
Page 263: ...B Statusand ErrorMessages StatusandError Messages...
Page 268: ...B 6 Status and Error Messages...
Page 269: ...C Measurement Considerations Measurement Consider ations...
Page 278: ...C 10 Measurement Considerations...
Page 279: ...D Model182Emulation Commands Model182 EmulationCom mands...
Page 284: ...D 6 Model 182 Emulation Commands...
Page 285: ...E Example Programs ExamplePro grams...
Page 293: ...F IEEE 488 BusOverview IEEE 488Bus Overview...
Page 307: ...G IEEE 488andSCPI ConformanceInformation IEEE 488and SCPIConform anceInforma tion...
Page 310: ...G 4 IEEE 488 and SCPI Conformance Information...
Page 311: ...H Measurement Queries Measurement Queries...
Page 316: ...H 6 Measurement Queries...
Page 317: ...I Delta PulseDelta and DifferentialConductance Delta Pulse Deltaand Dif ferentialCon ductance...