User manual

Audio Analyzer
AM700 Audio Measurement Set User Manual
4-63
When a frequency sweep is selected the Frequency choice in the Minimum Rise/Fall
menu is enabled, and when an amplitude sweep is selected the Amplitude choice in
enabled.
Minimum Sweep Rise/Fall. Specify the frequency or amplitude rise or fall (as
determined by the direction choice in the External Sweep Attributes menu) that
must occur to indicate the start of a new sweep. The default minimum rise/fall
settings are defined in the instrument specifications.
The sweep source can be either the internal generator or an external sweep source.
Generator. The Generator/External selection in Sweep Controls is for either
Generator (closed-loop) or External (open loop). When in closed-loop mode, the
Analyzer drives the Generator. A text line in the Generator Sweep Controls menu
display, “Sweep timing is being controlled by Analyzer” tells you that the Analyzer
is operating in a closed loop with the generator. During a sweep, additional feedback
is provided in the measurement view beneath the Measurement name. For those
measurements that have Generator as the selected source, the words “Controlling
Generator” are added.
In closed-loop mode, when a sweep is started, the generator begins at the first step
in the sweep. The analyzer waits for the delay time (set in the Settling settings), then
looks for settled data. When the data has settled, the generator is advanced to the
next frequency step. Now the analyzer uses the variance settings (amplitude or
frequency) or delay setting (whichever comes first) to determine when a change
occurs. After it sees a signal change that is larger than that defined by the variance
setting (either frequency or amplitude as specified), the analyzer begins looking for
settled data again. And again, when found, the generator is advanced to the next
step.
All enabled closed-loop measurements, displayed or not, must either find settled
data or time out at each generator step to permit the generator to advance to the next
step. This process continues for each generator step to the end of the sweep. An
illustration of these steps is shown in Figure 4-26 on page 4-65.
Closed-Loop Operating Hint. All enabled measurements, displayed or not, need to
find settled data or time out before the generator is allowed to advance to the next
step. Since some measurements take longer to make than others, you should be sure
that only the needed measurements are enabled.
Sweep Source