HDO9000 High Definition Oscilloscopes Operator's Manual
Example:
When a 1 GHz input with DC1Ω coupling is lowered from 2.5 GS/s to 1 GS/s in HD
Mode, a 500 MHz anti-aliasing filter is applied to maintain the 10-bit resolution. If the sample
rate is further lowered to 500 MS/s, bandwidth is filtered to 250 MHz.
A half bit of resolution is gained every time the bandwidth is halved. You can reduce or eliminate the
need to apply anti-aliasing filters to some channels by manually lowering the bandwidth on others,
also helping to maximize resolution. This approach is helpful when your test setup requires more
than two active channels, but you don't need full bandwidth on all (for example, a Qualifying signal for
triggering on C1 in addition to C2 and C3 for acquisition). You can selectively apply bandwidth filters
on the C
x
and Channel Setup dialogs.
When anti-aliasing filters are in operation, the Channel descriptor box will show the BWL symbol, the
same as when you manually select to limit bandwidth.
HD Descriptor Box
The resolution for which the instrument is optimized is shown on the HD descriptor box, which
appears whenever HD Mode is On. This box will always show 9 or 10 Bits, regardless of the actual
bits of resolution on any channel. The HD descriptor is hidden when HD Mode is Off.
Touch the HD descriptor box to open the HD Summary dialog.
HD Summary Dialog
The HD Summary dialog shows a breakdown of the factors that impact resolution on each channel. It
displays the:
l
Current
Bandwidth
at which the channel is operating due to the combination of manual
bandwidth filters, anti-aliasing filters, coupling setting, and timebase
l
Number of bits resolution for which the
ADC Configuration
is optimized due to the Active
Channels selection
l
The number of bits of resolution gained due to all the
Optimized Filtering
of bandwidth on that
channel (combined anti-aliasing and manual bandwidth filters)
l
The total
Resolution
at which the channel is operating (the sum of ADC Configuration and
Optimized Filtering)
Touch the
C
x
button to open the respective channel setup dialog and manually adjust bandwidth
filters or coupling.
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