However, the statistical significance of a continuous average is less
good, since the last acquired waveform has more weight than all
previously acquired ones. Thus the continuous average is dominated by
the statistical fluctuations of the most recently acquired waveforms.
The continuous average never stops at a maximum number of sweeps. The
weight of "old" waveforms gradually tends to zero, but they are
theoretically never completely forgotten. The averaging process may be
interrupted by switching the trigger mode from NORM to SINGLE (29)
by turning the function trace OFF (48). Averaging will continue when
these actions are reversed. The currently accumulated average may be
reset by either changing an acquisition parameter, such as input gain,
offset or coupling, trigger condition or the time base, or by pressing
the RESET push button (41) twice in quick succession (remember that
FUNCTION E or F must be selected).
Continuous averaging may be performed over CHANNEL 1 or 2. FUNCTION F
may also average over FUNCTION E, therefore allowing averaging over
functions.
10.2.3 Bxtrema
The computation of extrema consists of a repeated comparison of
recurrences of the source waveform with the already accumulated extrema
waveform. Whenever a given data point of the new waveform exceeds
(either positively or negatively) the corresponding data point of the
accumulated extrema waveform, it replaces the former value in the
extrema waveform. Thus a maximum (called "roof") or a minimum (called
"floor") envelope of all waveforms is accumulated.
Whenever the maximum number of waveforms is reached, the accumulation
process stops. The accumulation process may be interrupted by switching
the trigger mode from NORM to SINGLE (29) or by turning the function
trace OFF (48). Accumulation will continue when these actions are
reversed. The currently accumulated extrema waveform may be reset by
either changing an acquisition parameter, such as input gain, offset or
coupling, trigger condition or the time base, or by pressing the RESET
push button (41) twice in quick succession (remember that FUNCTION E
F must be selected). The number of currently accumulated waveforms is
displayed in the Displayed Trace Field (V in Figure 4.1) of the
corresponding function or of its expansion.
Whenever the maximum number of sweeps is reached, a larger number of
sweeps may be accumulated by simply changing the maximum number of
sweeps in the setup menu. In this case, care must be taken to leave the
other parameters unchanged, otherwise the extrema calculation is
started again.
WPOI Waveform Processing Option
10-5
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