Keithley 2450 Reference Manual page 292

Model 2450 Interactive SourceMeter® Instrument Reference Manual Section 4: Source-measure considerations
The connections for the floating configuration are shown below. To float the SMU, FORCE and
SENSE LO must be isolated from chassis ground. To do this, do not connect FORCE and SENSE LO
to chassis ground.
Figure 118: Connections for floating the instrument
The external voltage source can be a SMU of a second Model 2450 instrument or other instrument.
Keep in mind that if the combined outputs of the sources exceeds 42 V, a safety shield is required for
the DUT (see the following warnings).
The maximum floating (common mode) voltage for a SMU is ±250 V. Exceeding this level may
cause damage to the instrument and create a shock hazard.
Using an external source to float a SMU could create a shock hazard in the test circuit. A
shock hazard exists whenever >42 V peak is present in the test circuit. Appropriately rated
cables or insulators must be provided for all connections to prevent access to live parts.
When >42 V is present, the test circuit must be insulated for the voltage used or surrounded
by a metal safety shield that is connected to a known protective earth (safety ground) and
chassis ground (see (on page 4-10)).
Safety shield
2450-901-01 Rev. B/September 2013 4-13