Figure 12: Row-Column, Local Sense Connection Scheme example
Instrument card scheme for local sense
Use local sense when the measurement-pathway resistance is small and the associated voltage
errors are negligible. The measurement pathway is comprised of the following conductors, connected
in series:
• The cables used to connect the instruments to the matrix
• The internal matrix-card signal path
• The cables used to connect the matrix to the prober or test fixture
Current flowing through the measurement pathway creates a voltage drop (an error voltage) that is
directly proportional to the pathway resistance. This error voltage is present in all local sense voltage
measurements.
When local sense is selected, only the connection paths specified by the connected action are
completed. For example, in the figure in Switch matrix control (on page 2-16), the specified
connection paths would be:
• SMU2, 6 (connect SMU2 to Pin 6)
• GNDU, 3 (connect GNDU to Pin 3)
For the instrument card scheme, both the instrumentation and the prober/text-fixture pins or DUT are
connected to switch-matrix columns. No external connections are made to matrix rows. In this
configuration, two switch relays are closed to complete a path from an instrument to a DUT.
Instrument signals route to the prober/test-fixture pins through two or more matrix cards, as shown in
the following figure. This connection scheme can support large systems with numerous instruments
by removing the eight-row instrument connection limitation.
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