Keithley 2651A

Model 2651A High Power System SourceMeter® Instrument Reference Manual Section 3: Functions and features
2651A-901-01 Rev. A / March 2011 3-25
In this example:
A = 0, V
start
= 1, V
end
= 10, N = 5
Using the formula above, k = 1
Step size (b) for the sweep in the above figure is calculated as follows:
Log Step Size
log10(stop-0) log10(start-0)–
Points 1–
-----------------------------------------------------------------------------=
log10(10) log10(1)–
51–
-----------------------------------------------------=
10–()
4
-----------------=
0.25=
⎝⎠
⎜⎟
⎜⎟
⎜⎟
⎜⎟
⎜⎟
⎜⎟
⎜⎟
⎜⎟
⎛⎞
Therefore, b = 10
(log step size)
= 1.7783
The five log steps for this sweep are listed in the Logarithmic sweep points table below.
Logarithmic sweep points
Source point (N) Source level (V) Step number (i)
1 1 0
2 1.7783 1
3 3.1623 2
4 5.6234 3
5 10 4
When this sweep starts, the output will go to the start level (1 V) and sweep through the symmetrical
log points.
To configure a logarithmic staircase sweep, use the smuX.trigger.source.logY()function. This
function configures the source values the source-measure unit (SMU) will output when performing a
logarithmic sweep. After configuring the sweep, you must also enable the source action by setting the
following attribute:
smua.trigger.source.action
Example:
-- Sweep from 1 to 10 V in 10 steps with an asymptote of 0 V.
smua.trigger.source.logv(1, 10, 11, 0)
-- Enable the source action.
smua.trigger.source.action = smua.ENABLE
For more information, see smuX.trigger.source.logY().