Keithley 7021 Instruction Manual page 55

Operation
Four-wire resistance tests
More precise measurements over a wider range of system and
DUT conditions can be obtained by using the four-wire mea-
surement scheme shown in Figure 5-6. Here, separate sense
leads from the Model 2000 DMM are routed through the
multiplexer to the resistor under test. The extra set of sense
POWER
Figure 5-6
Four-wire resistance testing
5-8
Artisan Scientific - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisan-scientific.com
Input HI
Sense
Ω 4 Wire
HI
LO
Model 2000
Input LO
DMM
Sense
Ω 4 Wire
LO
A. Test Configuration
Input HI
Sense Ω 4 Wire HI
Ω
Sense Ω 4 Wire LO
Input LO
Model 2000
DMM
B. Simplified Equivalent Circuit
leads minimizes the effects of voltage drops across the test
leads. Note, however, that an extra two poles of switching are
required for each resistor tested. For this reason, only 12 re-
sistors per card can be tested using this configuration be-
cause two channels must close at the same time.
7021
1
12
HI
13
24
Dual 1x12 MUX
Note: Jumpers between Banks A
and B are removed.
DUT
7021
1
12
DUTs
(12)
R