Keithley SourceMeter 2600 Series Reference Manual page 188

6-12 Range, Digits, Speed, Rel, and Filters
Filters
Filter lets you set the filter response to stabilize noisy measurements. The
SourceMeter uses a digital filter, which is based on reading conversions. The
displayed, stored, or transmitted reading is an average of many reading
conversions (from 1 to 100).
Filter types
There are two averaging filter types to choose from: repeating and moving
(Figure
(filter count) is filled, and the conversions are averaged to yield a reading. The
stack is then cleared, and the process starts over.
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 re-averaged, yielding a new reading.
When the filter is first enabled, the stack is empty. Keep in mind that a filtered
reading is not yielded until the stack is full. The first reading conversion is placed
in the stack and is then copied to the other stack locations in order to fill it. Thus,
the first filtered reading is the same as the first reading conversion. Now the
normal moving average filter process can continue. Note that a true average is not
yielded until the stack is filled with new reading conversions (no copies in stack).
For example, in
reading conversions. The first nine filtered readings are calculated using copied
reading conversions.
Response time considerations
The filter averaging mode and count affect the overall reading speed. The moving
averaging filter is much faster than the repeat averaging filter because the unit
does not have to refill the filter stack for each reading. Also, the number of
readings averaged will affect reading speed; as the number of readings averaged
increases, the reading speed decreases.
Front panel filter control
Configuring filter
Filter type and count is configured from the filter configuration menu. The
configured filter is the same for all measurement functions.
2600S-901-01 Rev. A / May 2006
6-1). For the repeating filter (which is the power-on default), the stack
Figure 6-1A, it takes ten filtered readings to fill the stack with new
Return to
Series 2600 System SourceMeters Reference Manual
Section 6 topics