Acquiring and Displaying Waveforms
3–26 TDS 684A, TDS 744A, & TDS 784A User Manual
Press RUN/STOP button only (side) to use the RUN/STOP button to start
or stop acquiring. Pressing the RUN/STOP button once will stop the
acquisitions. The upper left hand corner in the display will say “Stop” and
show the number of acquisitions. If you press the button again, the oscillo-
scope will resume taking acquisitions.
Press Single Acquisition Sequence (side). That selection lets you run a
single sequence of acquisitions by pressing the RUN/STOP button. In
Sample, Peak Detect, or Hi Res mode, the oscilloscope will acquire a
waveform record with the first valid trigger event and stop. (Peak Detect and
Hi Res are only available on TDS 700A models.)
In Envelope or Average mode, the oscilloscope will make the specified
number of acquisitions to complete the averaging or enveloping task.
TDS 700A models only: If the oscilloscope is in equivalent-time mode and
you press Single Acquisition Sequence (side), it will continue to recognize
trigger events and acquire samples until the waveform record is filled.
NOTE. To quickly select Single Acquisition Sequence without displaying the
Acquire and Stop After menus, press SHIFT FORCE TRIG. Now the RUN/STOP
button operates as just described. (You still must display the Acquire menu and
then the Stop After menu to leave Single Acquisition Sequence operation.)
Press Limit Test Condition Met (side) to acquire waveforms until
waveform data exceeds the limits specified in the limit test. Then acquisition
stops. At that point, you can also specify other actions for the oscilloscope to
take, using the selections available in the Limit Test Setup main menu.
NOTE. In order for the oscilloscope to stop an acquisition when limit test
conditions have been met, limit testing must be turned ON using the Limit Test
Setup main menu.
Setting up limit testing requires several more steps. See Limit Testing, on
page 3–137.
Under certain conditions, a waveform may be aliased on screen. Read the
following description about aliasing and the suggestions for preventing it.
About Aliasing. When a waveform aliases, it appears on screen with a frequency
lower than the actual waveform being input or it appears unstable even though
the light next to TRIG’D is lighted. Aliasing occurs because the oscilloscope
cannot sample the signal fast enough to construct an accurate waveform record.
(See Figure 3–16.)
Preventing Aliasing