Keithley 2651A Reference Manual page 121

Section 3: Functions and features
Statistic attributes
Use the smua.buffer.getstats() function to access the reading buffer data statistics. The table
below displays the attributes that you can use to access the reading buffer data.
The returned parameter has the following attributes:
Attributes for accessing reading buffer data
Attribute
n
mean
stddev
min
max
If n equals zero (0), all other attributes will be nil because there is no data to base any statistics on.
If n equals 1, the stddev attribute will be nil because the standard deviation of a sample size of 1 is
undefined.
The min and max entries each have the following attributes:
Min and max entry attributes
Attribute
measurefunction
measurerange
reading
sourcefunction
sourceoutputstate
sourcerange
sourcevalue
status
timestamp
bufferVar is the name of the buffer. See
3-14
Model 2651A High Power System SourceMeter® Instrument Reference Manual
When returned Description
Always The number of data points on which the statistics are based
The average of all readings added to the buffer
When n > 0
The standard deviation of all readings (samples) added to the buffer
When n > 1
When n > 0 A table containing data about the minimum reading value added to the
buffer
A table containing data about the maximum reading value added to the
When n > 0
buffer
Description
String indicating the function measured for the reading (current, voltage,
ohms or watts)
The full-scale range value for the measure range used when the
measurement was made
The reading value
String indicating the source function at the time of the measurement
(current or voltage)
String indicating the state of the source (off or on)
Full-scale range value for the source range used when the
measurement was made
If bufferVar.collectsourcevalues is enabled, the sourced value
in effect at the time of the reading
Status value for the reading; the status value is a floating-point number
that encodes the status value into a floating-point value
If bufferVar.collecttimestamps is enabled, the timestamp, in
seconds, between when the reading was acquired and when the first
reading in the buffer was acquired; adding this value to the base
timestamp will give the actual time the measurement was acquired
smuX.buffer.getstats() (on page 7-172) for additional information.
2651A-901-01 Rev. A / March 2011