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Ratio and Delta 5-23

Figure 5-10

Test circuit—Fixed H (Vary I)

The readings in the buffer of Model 2182 #1 correspond to the current sweep values. You can

then use the buffer location numbers to reference DUT readings to current amplitudes:

Model 2182 #1 Buffer Model 2182 #2 Buffer

RDG NO. 1 = 1mV ⇒ 10µA RDG NO. 1 = DUT measurement

RDG NO. 2 = 2mV ⇒ 20µA RDG NO. 2 = DUT measurement

RDG NO. 3 = 5mV ⇒ 50µA RDG NO. 3 = DUT measurement

Delta measurements — As previously explained, the DC current reversal measurement

technique must be used to cancel the effects of thermal EMFs in the test leads. By conﬁguring

a custom sweep, the SourceMeter can function as a bipolar, growing amplitude source.

For example, if the test requires current steps of 10µA, 20µA, and 50µA, the 6- point custom

sweep would be conﬁgured as follows:

P0000 = +10µA P0001 = –10µA

P0002 = +20µA P0003 = –20µA

P0004 = +50µA P0005 = –50µA

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.

2182 #2

CH 1

SourceMeter

Source ±I

Thermal

EMFs

30´ Cables

DUTH

<4K

Cryostat

HI LO

2182 #1

CH 1

1mA

100Ω

REF

Keithley 2182 User Manual

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