Model 2657A High Power System SourceMeter® Instrument Reference Manual
Section 3: Functions and features
2657A-901-01 Rev. B/December 2012
3-3
Filter types
The Model 2657A has three filter types. These three filter types are broken down into two averaging
filters and one median filter.
The two averaging filters are repeating and moving (see figure below). For the repeating filter (which
is the power-on default), the stack (filter count) is filled, and the conversions are averaged to yield a
reading. The stack is then cleared, and the process starts over.
Figure 30: Repeating and moving average filters
The moving average filter uses a first-in, first-out stack. When the stack (filter count) becomes full, the
measurement conversions are averaged, yielding a reading. For each subsequent conversion placed
into the stack, the oldest conversion is discarded. The stack is averaged again, yielding a new
reading.
The median filter is used to pass the “middle-most” reading from a group of readings that are
arranged according to size. The median filter uses a first-in, first-out stack similar to the moving
average filter. For each subsequent conversion placed into the stack, the oldest conversion is
discarded. The median is then redetermined.
Conversion
#1
#1
#1
#1
#1
#1
#1
#1
#1
Conversion
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Reading
#1
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B. Type: Moving average, readings = 10
Conversion
#2
#1
#1
#1
#1
#1
#1
#1
#1
Conversion
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Reading
#2
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•
•
Conversion
#3
#2
#1
#1
#1
#1
#1
#1
#1
Conversion
#1
Reading
#3
•
•
•
Conversion #10
#9
#8
#7
#6
#5
#4
#3
#2
Conversion
#1
Reading
#1
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A. Type: Repeating, readings = 10
Conversion #20
#19
#18
#17
#16
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#14
#13
#12
Conversion #11
Reading
#2
•
•
•
Conversion #30
#29
#28
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#23
#22
Conversion #21
Reading
#3
•
•
•
Conversion #10
#9
#8
#7
#6
#5
#4
#3
#2
Conversion
#1
Reading
#10
•
•
•
Conversion #11
#10
#9
#8
#7
#6
#5
#4
#3
Conversion
#2
•
•
•
Reading
#11
Summary of Contents for 2657A
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