Model 2651A High Power System SourceMeter® Instrument Reference Manual Section 7: Command reference
2651A-901-01 Rev. A / March 2011 7-245
Also see
smuX.trigger.source.action (on page 7-241)
smuX.trigger.source.linearY()
(on page 7-243)
smuX.trigger.source.logY()
(on page 7-245)
Sweep Operation
(on page 3-19)
smuX.trigger.source.logY()
This function configures an exponential (geometric) source sweep.
Type TSP-Link accessible
Affected by Where saved Default value
Function Yes
Usage
smuX.trigger.source.logY(startValue, endValue, points, asymptote)
X
Source-measure unit (SMU) channel (for example, smua.trigger.source.logv(1,
10, 11, 0) applies to SMU channel A)
Y
SMU source function (v = voltage, i = current)
startValue
Source value of the first point
endValue
Source value of the last point
points
The number of points used to calculate the step size
asymptote
The asymptotic offset value
Details
This function configures the source action to be a geometric source sweep in a subsequent sweep. During the
sweep, the source will generate a geometric series of ascending or descending voltage or current changes called
steps. Each step is larger or smaller than the previous step by a fixed proportion. The constant of proportionality
is determined by the starting value, the ending value, the asymptote, and the number of steps in the sweep. The
number of source steps is one less than the number of sourced points.
The points parameter does not set the number of steps in a sweep, but rather is used to calculate source
values within a subsequent sweep. If the subsequent sweep has more points than specified in points, the
source will restart at the beginning. This means that if the trigger count is greater than the number of points in a
sweep as configured, the SMU will satisfy the trigger count by restarting the sweep values from the beginning.
If the subsequent sweep has fewer points than specified in points, endValue will not be reached during the
sweep. This means that if the trigger count is less than the number of source values configured, the SMU will
satisfy the trigger count and ignore the remaining source values.
In cases where the first sweep point is non-zero, it may be necessary to precharge the circuit so that the sweep
will return a stable value for the first measured point without penalizing remaining points in the sweep.
With logarithmic sweeps, it is usually necessary to allow the source to autorange to maintain good source
accuracy when sweeping over more than one decade or across range boundaries.
The asymptote parameter can be used to customize the inflection and/or offset of the source value curve. This
allows log sweeps to cross zero. Setting this parameter to zero provides a conventional logarithmic sweep. The
asymptote value is the value that the curve would have at either positive or negative infinity depending on the
direction of the sweep.
The asymptote value must not be equal to or between the starting and ending values. It must be outside the
range defined by the starting and ending values.
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