Keithley 7072 Instruction Manual page 46

OPERATION
COLUMNS
------
Current Source
7072
Card
Warning : Outer fixture must be -
used to avoid possible
shock hazard from guard.
Figure 2-24. Typlcal Guarded Signal Connections
2.7.8 Matrix Expansion Effects on Card
Specifications
Specifications such as those given for path isolation and
offset current are with a single Model 7072 Card installed
in the mainframe. Expanding the matrix by internally or
externally connecting two or more Model 7072 Cards
together will degrade system performance specifications
(other types of cards do not affect the specifications
because they use different pathways in the mainframe
backplane). The extent depends on how many cards are
used, as well as the amount of cabling used to connect
them together.
With internal row expansion, isolation among rows is
decreased, and offset current is increased, although the
isolator relays on the card do help to minimize these ef-
fects. With external row or column expansion, isolation and
offset current specifications are degraded because of the
additional parallel paths and relays present on each signal
line.
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