Matrix Configuration; Switching Matrix; Path Isolators; Equivalent Circuit Of Test Fixture Connections - Keithley 7174A Instruction Manual

Operation

Figure 2-13

Equivalent circuit of test fixture connections
2.6 Matrix configuration
This section describes the matrix configuration of the Model
7174A. It also explains ways to expand the matrix by install-
ing and connecting additional matrix cards in the Model
707A Switching Matrix.

2.6.1 Switching matrix

As shown in Figure 2-14, the Model 7174A is organized as
an 8 × 12 (8 rows by 12 columns) matrix. The rows on the
card are labeled A through H while the columns are num-
bered 1 through 12. The actual column number to use when
programming depends on the slot and unit number (Table
2-3). For example, card column number 2 on a card in slot 5
of unit 1 is accessed as matrix column 50.
2-18
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Triax Cable
Signal
Guard
From
7174A
Card
Chassis
Ground
Probe
Wafer
Test Fixture Chassis
Each intersecting point in the matrix is called a crosspoint
that can be individually closed or opened by programming
the Model 707A mainframe. By closing the appropriate cros-
spoint, required pathways and pins may be connected. All
crosspoints are configured for 2-pole switching, as shown in
Figure 2-14. SIGNAL and GUARD are switched separately
to any of the 12 columns on the card.

2.6.2 Path isolators

The path isolator relay switches shown in Figure 2-14 serve
to isolate a given path from the rest of the matrix when no
crosspoint (relay) is closed in that pathway. This topology
minimizes leakage current and capacitance to pathways
which are active. These isolators close automatically when
any crosspoint on the path is closed and open automatically
when all crosspoints on the path are opened.