Fluke DDS Function Generator 271, User Manual

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271
Users Manual
Auxiliary Output Phase
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Sine
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Square
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Triangle
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Ramp
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AUX 0°
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AUX 90°
0º 180º 360º
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AUX
180°
The convention adopted for phase in this
instrument is illustrated in the diagram. 0 ° is
always the first data point in waveform memory.
On symmetrical waveforms 0 ° is the rising edge
zero-crossing point for sine, square, triangle and
pulse waveforms; on ramps, staircases and
arbitrary waveforms 0 ° is always the start point.
When the phase is set to 0 ° the rising edge of the
AUX OUT
square wave is also at 0 °. When the
phase is set to a positive value, e.g. +90 °, the
AUX OUT
square wave lags
MAIN OUT
by 90°,
when the phase is set to a negative value
AUX OUT
leads
MAIN OUT
.
The phase is set by pressing the
EDIT
key
followed by
TRIG
to select the trigger edit menu;
the edit cursor is then moved to the PHASE field
using the
FIELD
keys. Phase can be entered
directly from the keyboard, using the +/- key to
change the sign if necessary, or by rotary control.
Above 30 kHz the
AUX OUT
accompanying sine,
triangle, square and pulse waveforms is
automatically switched such that it is derived from
the comparator (driven by the DDS sine wave)
used to generate higher frequency
MAIN OUT
square waves and pulses. The
DDS Principles
section gives further information. This ensures a
jitter-free
AUX OUT
signal up to the maximum
frequency of the generator but it also means that
phase shifting between
MAIN OUT
and
AUX OUT
is no longer possible.
This constraint can be overridden by changing the
setting on the
OPT
ions menu from
AUX OUTPUT=AUTO
to
AUX OUTPUT=LOW FREQ
; the
AUX OUT
signal then continues to be generated
independently, with phase adjustable with respect
to the
MAIN
output, although clock jitter will
become increasingly significant at higher
frequencies. Changing
AUTO
settings is
described more fully in the next section,
Waveform
Generator Options
.
The
AUX OUT
signal accompanying ramp,
staircase and arbitrary waveforms is, by default,
always generated independently; phase shift is
adjustable across the frequency range but again
clock jitter becomes increasingly significant at
higher frequencies
5-8
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