Acquisition Modes
TDS 620A, 640A, & 644A User Manual
To bring up the acquisition menu (Figure 3-2) press SHIFT ACQUIRE MENU.
Acquisition Mode
To choose how the digitizing oscilloscope will create points in the waveform
record:
Press SHIFT ACQUIRE MENU ➞ Mode (main) ➞ Sample, Peak Detect, Hi
Res, Envelope, or Average (side).
When you select Envelope or Average, you can enter the number of wave-
form records to be enveloped or averaged using the keypad or the general
purpose knob.
NOTE

If you selected the longest record length available in the Horizontal

menu, then you cannot select Hi Res as your acquisition mode. This

is because Hi Res mode uses twice the acquisition memory that the

other acquisition modes use. If Hi Res and the longest horizontal

record length were allowed to be selected at the same time, the

oscilloscope would run out of memory.

Repetitive Signal
To limit the digitizing oscilloscope to real-time sampling or let it choose be-
tween real-time or equivalent-time sampling:
Press SHIFT ACQUIRE MENU ➞ Repetitive Signal (main) ➞ ON or OFF
(side).
ON (Enable ET) uses both the real time and the equivalent time features
of the digitizing oscilloscope.
OFF (Real Time Only) limits the digitizing oscilloscope to real time
sampling. If the digitizing oscilloscope cannot accurately get enough
samples for a complete waveform, the oscilloscope will use the interpola-
tion method selected in the display menu to fill in the missing record
points. That is, it will use either the linear or sin(x)/x interpolation algo-
rithm.
See
Acquisition
on page 2-19 for details about sampling.
Stop After
You can choose to acquire exactly one waveform sequence or to acquire
waveforms continuously under manual control.
Press SHIFT ACQUIRE MENU ➞ Stop After (main) ➞ RUN/STOP button
only, Single Acquisition Sequence, or Limit Test Condition Met (side)
(see Figure 3-3).
Operation