Keithley 2651A Reference Manual page 129

Section 3: Functions and features
Example:
-- Sweep from 0 to 10 V in 1 V steps.
smua.trigger.source.linearv(0, 10, 11)
-- Enable the source action.
smua.trigger.source.action = smua.ENABLE
For more information, see smuX.trigger.source.linearY() (on page 7-243).
Logarithmic staircase sweeps
This type of sweep is similar to the linear staircase sweep. The steps, however, are done on a
logarithmic scale.
Like a linear staircase sweep, logarithmic sweeps are configured using a start level, a stop level, and
the number of points. The step size is determined by the start and stop levels, and the number of
sweep points. However, in a logarithmic sweep, the step size increases or decreases exponentially.
To create an increasing logarithmic sweep, set the stop value to be greater than the start value. To
create a decreasing logarithmic sweep, set the stop value to be less than the start value. A
measurement is made at each step after source and measurement settling time. An asymptote can
also be used to control the inflection of a sweep.
The number of sweep steps actually performed is determined by the trigger count. See
page 3-32) for more information.
The formula for a logarithmic sweep is:
Where:
= The source value at source point i
v
i
= The number of points in the sweep
i
= The number of points in the sweep
N
= The initial source value as an offset from the asymptote
k
= The step size ratio
b
= The asymptote value
A
The asymptote is used to change the inflection of the sweep curve and allow it to sweep through zero.
Both of the following figures depict the effect of the asymptote on the inflection of the sweep curve.
The following two figures show sample sweeps.
3-22
Model 2651A High Power System SourceMeter® Instrument Reference Manual
NOTE
i
v = A + kb
i
Triggering
2651A-901-01 Rev. A / March 2011
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