74 SDA-OM-E Rev H
SMART Memory Setup
1. Touch Timebase in the menu bar, then SMART Mem Setup... in the drop-down menu.
2. Touch the SMART Memory tab.
3. Under Timebase Mode, touch the Set Maximum Memory or Fixed Sample Rate button.
Information about your choice appears below the buttons. The calculated memory length and
time per sample point appear below the scroll buttons.
4. Touch inside the Time/Division data entry field and set a time per division.
Note: If you are currently acquiring waveforms, you will notice a change in sampling rate as you select different modes.
5. If you selected Sequence mode, touch inside the Num Segments data entry field and enter
a value using the pop-up numeric keypad. If you want to use a timeout period, touch the
Enable Timeout checkbox; then touch inside the Timeout data entry field and enter a value.
External Timebase vs. External Clock
An external timebase reference is used to synchronize the scope's internal timebase to an
external frequency source. This allows multiple instruments to lock their timebases to a common
source. The external timebase reference frequencies are model dependent. For example, the
WaveMaster, SDA, and DDA series instruments use 100 MHz ±0.001%, and the voltage level
required is 650 mV
pk-pk
or 0.0 dBm ±30%. On the other hand, the WavePro 7000A series uses an
external timebase reference of 10 MHz ±0.01% with an amplitude of 650 mV
pk-pk
or 0.0 dBm
±30%. The external timebase reference is applied to the rear panel BNC connector.
Note: An external timebase reference cannot be applied to the SDA 18000/13000/11000/9000 when operating in DBI
mode.
An external sampling clock, applied via the auxiliary input, replaces the scope's internal timebase
as the sampling clock. This means that the external sampling clock controls when the scope's
digitizers sample the input waveforms. The frequency range of the external sampling clock is
model dependent: WaveMaster, SDA, DDA, and WavePro 7000A series scopes require a signal
frequency between 30 MHz and 2 GHz. However, the WaveRunner 6000A series scopes accept
an external sampling clock between DC and 1 GHz. In all cases, the external sampling clock
levels are TTL, ECL, or 0 volt crossing 650 mV
pk-pk
or 0.0 dBm ±30%. Since the external
sampling clock uses the auxiliary input, an external trigger cannot be used when the external
sampling clock is in use.
TRIGGERING
TRIGGER SETUP CONSIDERATIONS
Trigger Modes
Auto mode causes the scope to sweep even without a trigger. An internal timer triggers the
sweep so that the display remains, even when the signal does not cause a trigger.
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