PSI System Controls and Diagnostics
F3200E User Manual
F3200E_UM_180726 Page 28 of 107
Trigger
Buffered
data
Successive ADC conversions
Time
Figure 9. Data acquisition in buffered mode
Sweep mode
is designed for situations where there is a repetitive signal, synchronized to some
trigger. An example is a scanned charged particle beam which repeatedly passes over apertures
in front of Faraday collectors. In this circumstance, we can average across multiple scans
without loss of time resolution. The mode is analogous to the averaging mode of digital storage
oscilloscopes. Each block of data (a sweep) can be up to 1000 samples, which corresponds to 1
msec of contiguous data at 1 MHz ADC rate, and thus a data rate to the host PC of about 1 kHz.
You can average up to 65534 sweeps together to improve the signal to noise ratio, and the data
rate to the host PC is correspondingly reduced. Thus if you average 1000 sweeps, each of 100
samples taken at 1 MHz ADC rate, the data rate will be about 10 Hz.
To sample longer events in each sweep, you can reduce the ADC rate; for example 1000 samples
at 10 kHz ADC rate would give 0.1 seconds for each sweep.
Figure 10 shows a simplified schematic representation of sweep mode in which three sweeps are
averaged, each with just six samples across the sweep (1000 is the more typical number). Note
that there is no requirement that the triggers are equally spaced in time, only that the signals in a
sweep are synchronized to their initiating trigger.
