2600AS-901-01 Rev. B / September 2008 Return to Section Topics 9-5
Series 2600A System SourceMeter® Instruments Reference Manual Section 9: Sweep Operation
Logarithmic staircase sweeps
This sweep is similar to the linear staircase sweep. The steps, however, are done on a logarithmic
scale.
Figure 9-3 and Figure 9-4 show sample sweeps.
Like a linear staircase sweep, logarithmic sweeps are configured using a start level, a stop level
and the number of points in between. 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.
NOTE The number of sweep steps actually performed is determined by the
trigger count. See Section 10 for more information.
The formula for a log sweep is:
v
i
= A + kb
i
Where: v is the source value at source point i.
i ranges from 0 to N-1.
N is the number of points in the sweep.
k is the initial source value as an offset from the asymptote.
b is the step size ratio.
A is the asymptote value.
The asymptote is used to change the inflection of the sweep curve and allow it to sweep through
zero.
Figure 9-3 and Figure 9-4 depict the effect of the asymptote on the inflection of the sweep
curve.
Figure 9-3
Increasing logarithmic sweep
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
12345678
Point
2 to 8 with A = 0
2 to 8 with A = 1.8
2 to 8 with A = 8.5
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