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Acquiring and Displaying Waveforms
3–34
TDS 500C, TDS 600B, & TDS 700C User Manual
NOTE. TDS 500C and 700C models only: Selecting Hi Res mode in the Acquire
menu automatically reduces long record-length settings to prevent overflow of
acquisition memory. Because Hi Res mode uses twice the acquisition memory
used by other acquisition modes, allowing selection of the longer horizontal
record lengths with Hi Res mode would cause the oscilloscope to run out of
memory.
TDS 500C and TDS 700C models only: To limit the oscilloscope to real-time
sampling or let it choose between real-time or equivalent-time sampling:
Press SHIFT ACQUIRE MENU ➞ Repetitive Signal (main) ➞
ON or OFF (side).
H ON (Enable ET) uses both the real-time and the equivalent-time sampling
as appropriate (see Table 3–4).
H OFF (Real Time Only) limits the oscilloscope to real-time sampling. If the
oscilloscope cannot accurately get enough samples for a complete waveform,
it will interpolate.
NOTE. The oscilloscope will use the interpolation method selected in the display
menu to fill in the missing record points — either linear or sin(x)/x interpolation.
See Interpolation on page 3–28 for a discussion of interpolation.
The sampling speeds and the number of channels you choose affect the mode the
oscilloscope uses to sample waveforms:
H The oscilloscope always real-time samples at slower time base settings;
faster time settings force the oscilloscope to switch from real-time sampling
to equivalent-time sampling or interpolation, depending on whether ET is on
or off.
H The oscilloscope extends the limit at which it must switch from real-time
sampling by using the digitizers of channels that are turned off to sample the
channel or channels that are turned on.
Selecting Repetitive
Sampling