HP 54645A, User'S And Service Manual

Page: 282 / 301

Sweep speed (time base) is the
amount of time per division on the
display, and is shown on the status
line. When you vary the Time/Div set-
ting while running an acquisition, the
sample period is also being adjusted.
Thresholds define the voltage at
which there is a change from low to
high. Thresholds specified can be
TTL, CMOS, or ECL, or variable from
-6.0 V to +6.0 V.
Time base See “Sweep speed.”
Trigger is the point that causes
the oscilloscope to begin storing ac-
quisition data. The trigger can be a
signal edge, a pattern, or a combina-
tion of edges, patterns, and
durations. See “Edge trigger,” “Pat-
tern trigger,” or “Advanced trigger.”
Width refers to positive and nega-
tive duration of a signal. The signal
width can be measured using time
measurements. In doing so, the oscil-
loscope measures the time between
the first set of transitions at the left
side of the visible display that begin
and end the logic high or low value.
See also “Minimum detectable pat-
tern width.”
HP 54645A/D Oscilloscope Terms
Acquisition memory stores the
acquired sample. This memory is
part of the acquisition subsystem,
and is located in the sample RAM.
Aliasing is occurring whenever
the waveform display changes more
than expected, as you expand the
time base. Aliasing is due to under
sampling.
Auto is a trigger mode that pro-
duces a baseline display if the trigger
conditions are not met. If the trigger
frequency is less than 25 Hz, even if
the level and slope conditions are
met, a free-running display will re-
sult.
Auto Level sets the trigger point
to the 50% amplitude point on the
displayed waveform. If there is no
signal present, a baseline is dis-
played.
Autoscale performs a simple one-
button setup of the oscilloscope,
including setting the time base and
thresholds and displaying waveforms
for channels connected to active sig-
nals.
Glossary
Glossary-3