User manual

PicoScope 6000 Series Programmer's Guide 19
Copyright © 2009-2013 Pico Technology Ltd. All rights reserved. ps6000pg.en r9
3.6
Oversampling
Note: This feature is provided for backward-compatibility only. The same effect can be
obtained more efficiently with the PicoScope 6000 Series using the hardware
averaging feature (see Downsampling modes).
When the oscilloscope is operating at sampling rates less than its maximum, it is
possible to oversample. Oversampling is taking more than one measurement during
a time interval and returning the average as one sample. The number of
measurements per sample is called the oversampling factor. If the signal contains a
small amount of wideband noise (strictly speaking, Gaussian noise), this technique
can increase the effective vertical resolution of the oscilloscope by n bits, where n is
given approximately by the equation below:
n = log (oversampling factor) / log 4
Conversely, for an improvement in resolution of n bits, the oversampling factor you
need is given approximately by:
oversampling factor = 4
n
An oversample of 4, for example, would quadruple the time interval and quarter the
maximum samples, and at the same time would increase the effective resolution by
one bit.
Applicability
Available in block mode only.
Cannot be used at the same time as downsampling.
3.7
Timebases
The API allows you to select any of 2
32
different timebases based on a maximum
sampling rate of 5 GHz. The timebases allow slow enough sampling in block mode to
overlap the streaming sample intervals, so that you can make a smooth transition
between block mode and streaming mode.
timebase
sample interval formula
sample interval examples
0 to 4
2
timebase
/ 5,000,000,000
0 => 200 ps
1 => 400 ps
2 => 800 ps
3 => 1.6 ns
4 => 3.2 ns
5 to 2
32
-1
(timebase - 4) / 156,250,000
5 => 6.4 ns
...
2
32
-1 => ~ 6.87 s
Applicability
Use ps6000GetTimebase API call.