Section 4: Sourcing and measuring Model 2601B-PULSE System SourceMeter Instrument Reference Manual
4-12 2601B-PULSE-901-01A April 2020
The signal present at the FORCE terminals is affected by the total inductance in the test circuit. The
signal present at the SENSE terminals is only affected by the inductance beyond the Kelvin
connection points. Take this into consideration when setting the voltage protection levels.
Keithley Instruments offers several low-inductance cable options that are optimized for
pulser applications:
• 2601B-PULSE-CA1 50 Ω BNC-to-BNC cable kit: A set of two 1.2 m BNC-to-BNC cables and
one 1.2 m cable assembly. Use the cables to make the SENSE HI and SENSE LO connections.
Use the cable assembly to make the FORCE HI and FORCE LO connections. On the end
intended for connection to the device under test (DUT), the shields on the cable kit are jumpered
to reduce loop inductance.
• 2601B-PULSE-CA2 50 Ω BNC-to-BNC coaxial cables: A set of two 3 m cables that are used to
make the SENSE HI and SENSE LO connections.
• 2601B-PULSE-CA3 15 Ω BNC-to-BNC cable kit: A set of two 3 m cables that are used to
make the FORCE HI and FORCE LO connections. On the end intended for connection to the
DUT, the shields are jumpered to remove loop inductance. The 2601B-PULSE-CA2 must be used
for the SENSE connections. This cable kit has lower inductance than the 2601B-PULSE-CA1.
Contact check connections
The contact check function prevents measurement errors due to excessive resistance in the force or
sense leads when 4-wire remote sensing is used. Potential sources for this resistance include poor
contact at the device under test (DUT), failing relay contacts on a switching card, and wires that are
too long or thin. To use contact check, the current limit must be at least 1 mA (this allows enough
current to flow when performing the test), and the source-measure unit (SMU) must not be in High-Z
output-off mode.
The contact check function also detects open circuits that may occur when a four-point probe is
misplaced or misaligned. This relationship is shown schematically in the figure below, where R
C
is the
resistance of the mechanical contact at the DUT, and R
S
is the series resistance of relays and cables.
Contact check requires both force and sense connections. Refer to 4-wire remote sensing
connections (on page 4-10) for information.
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