Model 2651A High Power System SourceMeter® Instrument Reference Manual Section 2: General operation
2651A-901-01 Rev. A / March 2011 2-59
WARNING
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 safety earth ground and chassis ground
(see Safety shield (on page 2-54)).
Output-off states
CAUTION
Carefully consider and configure the appropriate output-off state, source, and compliance levels
before connecting the Model 2651A High Power System SourceMeter
®
Instrument to a device that
can deliver energy such as other voltage sources, batteries, capacitors, solar cells, or other System
SourceMeter instruments. Program recommended instrument settings before making connections to
the device. Failure to consider the output-off state, source, and compliance levels may result in
damage to the instrument or to the device under test.
Output-off modes
Turning a source-measure unit (SMU) off may not completely isolate the SMU from the external
circuit. The output-off mode can be used to place the Model 2651A in a known, safe, non-interactive
state during idle periods, for example, when changing devices. A Model 2651A SMU can be in one of
three output-off modes: Normal, high-impedance, or zero.
Normal output-off mode
The NORMAL output-off mode is the default output-off mode setting. When the source-measure unit
(SMU) is in the NORMAL output-off mode, you can select either the CURRENT or the VOLTAGE
output-off function (see Output-off function
(on page 2-61)), and you can specify current and voltage
output-off limits (see Output-off limits
(on page 2-62)).
High-impedance output-off mode
For the high-impedance output-off mode (HI-Z), the output relay opens when the output is turned off.
This disconnects external circuitry from the input/output of the source-measure unit (SMU). To
prevent excessive wear on the output relay, do not use this output off state for tests that turn the
output off and on frequently.
Zero output-off mode
The Model 2651A is configured as described below when it is in the ZERO output-off mode.
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