Model 2657A High Power System SourceMeter® Instrument Reference Manual Section 2: General operation
2657A-901-01 Rev. B/December 2012 2-67
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 2657A SMU in a known, safe,
non-interactive state during idle periods, for example, when changing devices. A Model 2657A 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 2-68)). You can also specify current and voltage output-off
limits (Output-off limits (compliance)
(on page 2-69)).
When the output is turned off, the output goes to either 0 V or 0 A, depending on the selected output-
off function. Voltage is the default output-off function.
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 2657A is configured as described below when it is in the zero output-off mode.
When the V-Source is the selected source:
• The programmed V-Source value remains on the display.
• Internally, the V-Source is set to 0 V.
• The current compliance setting remains the same as the output-on value. Compliance detection
remains active.
• Measurements are performed and displayed.
When the I-Source is the selected source:
• The programmed I-Source value remains on the display.
• Internally, the V-Source is selected and set to 0 V.
• Current compliance is set to the programmed Source I value or to 10 percent full-scale of the
present current range, whichever is greater.
• Measurements are performed and displayed.
The Model 2657A can be used as an I-Meter when it is in zero output-off mode because it will output
0 V, but measure current.
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