Differential Switching; Sensing - Keithley 7021 Instruction Manual

Multiplexer Configuration

Differential switching

The differential or floating switching configuration is shown
in Figure 2-7. The advantage of using this configuration is
that the terminals of the source or measure instrument are not
confined to the same pathway. Each terminal of the instru-
ment can be switched to any available input in the test system.
HI
LO
Source or
Measure
Figure 2-7
Differential switching example
Source HI
Sense HI
Sense LO
Source LO
Source or
Measure
Figure 2-8
Sensing example
2-4
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Sensing

Figure 2-8 shows how the multiplexer can be configured to
use instruments that have sensing capability. The main
advantage of using sensing is to cancel the effects of switch
card path resistance (<1.25 Ω ) and the resistance of external
cabling. Whenever path resistance is a consideration, sensing
should be used.
Bank A
H
Out In
L
H
Out In
L
Bank B
7021
Bank A
H
Out
L
H
Out
L
Bank B
7021
DUT
In
DUT
In