Fluke 91 Series II User Manual page 106

Using Additional Capabilities 6 - 13
Filter Any waveform (active input or memory) can be
filtered, with the resulting waveform stored in a new
memory location. Noise suppression or simply waveform
smoothing is thereby possible. Filtering is especially useful
with single-shot waveforms, where averaging of multiple
waveform samples is not otherwise available. In the
following figure, the upper waveform represents the INPUT
A waveform as measured, and the lower waveform
represents the filtered version recalled from Waveform 4
memory.
NOTE
In FILTER function, the -3 dB frequency is 0.8/time-per-
division.