Figure 6-3 Repeat Filter (Count 10) - Keithley 6430 Instruction Manual

6-10 Range, Digits, Speed, and Filters
Repeat filter
The Repeat Filter places the specified number of measurement conversions into a stack and
averages them to yield a single Repeat Filter reading. The stack is then cleared, and the process
starts over. For example, if the repeat count (stack size) is 10, every 10 measurement conver-
sions will yield a single reading. Figure 6-3 illustrates the Repeat Filter process. The maximum
count (stack size) for the Repeat Filter is 100. Note that setting the count to one disables the
Repeat Filter.
Choose the Repeat Filter for sweeping so readings for other source levels are not averaged
with the present source level.
Figure 6-3
Conversion #10
Repeat filter
(count 10)
Conversion
Median filter
The Median Filter is used to pass the "middle-most" reading from a group of readings that
are arranged according to size. For example, assume the following readings:
2mA, 1nA, 3nA
The readings are placed in a stack, re-arranged in ascending order as follows:
1nA, 3nA, 2mA
From the above readings, it can be plainly seen that 3nA is the median (middle-most) read-
ing. Therefore, the 3nA reading is allowed to pass, while the other two readings are discarded
(filtered out). The Median Filter provides a good method to reject noise spikes.
The number of reading samples (stack size) for the Median Filter is determined by the
selected rank (1 to 5) as follows:
Sample readings = 2n + 1
Where; n is the selected rank (0 to 5)
#9
#8
#7
•
Repeat
#6
•
Reading
#5
•
#1
#4
#3
#2
#1
Conversion #20
#19
#18
#17
• Repeat
#16
•
Reading
#15
• #2
#14
#13
#12
Conversion #11
Conversion #30
#29
#28
#27
•
Repeat
#26
•
Reading
#25
•
#3
#24
#23
#22
Conversion #21