U1084A Datasheet, PDF (13/20 Pages) Keysight Technologies – Acqiris High-Speed PCIe Digitizers with On-Board Signal Processing

Noise suppressed accumulation
Segment accumulation
In some applications, such as time-of-flight spectroscopy,
the signal is a rare event sitting on top of a noisy baseline
and the averaging process reduces the random noise. As
a consequence, to enhance the digitizers ability to detect
such signals in the presence of synchronous noise, the
averaging firmware allows the user to set a threshold that
must be exceeded for each data value to be entered into
the sum.
Furthermore, to simplify overall system design in order to
avoid overflow in the summed data, the noise base can be
subtracted from each data value before the summation is
done. A similar capability is implemented for negative-going
signals.
In time-resolved applications where multiple averaged
waveforms must be acquired with very low dead time, the
averaging memory can also be segmented. This allows the
user to store from 1 up to 128 K separate accumulations of
summed data. The segment length is user-programmable.
In standard segment accumulation mode the user selects
the desired number of triggers per segment, N, up to over
16 million. The next segment accumulation will be started
after the previous N triggers have been processed.
The memory in the U1084A averager is optimized to allow
real-time acquisition and averaging. At the end of each
average segment, a dead time exists before a new average
can be stored. The dead time duration depends on the size
of the segment, a 162 KS segment will incur a 1 ms dead
time.
Treshold [V]
Baseline [V]
NSA
Value of interest = Sample Value - Baseline
Baseline [V]
Figure 3. Signal detection using noise suppressed
accumulation
Ping-pong accumulation
To increase measurement rates the U1084A with AVG firm-
ware will allow ping-pong accumulation and processing.
After the dead time, at the end of each segment accumula-
tion, a new accumulation can be started before readout of
the previous accumulation. While accumulation continues,
the previous segment can be read out through the high
speed PCIe bus at up to 520 MB/s.
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