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Copyright © 2007-2013 Pico Technology Ltd. All rights reserved.psw.en r32
Filter details
The lowpass filtering algorithm is chosen according to the ratio of the selected cut-off
frequency (f
C
) to the sampling rate (f
S
), as follows:
f
C
÷ f
S
Filter type
Description
0.0 to 0.1
Moving average
A moving average filter is used for low cut-off
frequencies. The length of the filter is adjusted to
achieve the selected cut-off frequency, which is
defined as the first minimum in the frequency
response. There is significant signal leakage above
the cut-off frequency. This filter changes a vertical
edge into a linear slope.
0.1 to < 0.5
FIR
A finite impulse response filter is used for medium
to high cut-off frequencies. This has a monotonic
roll-off above the cut-off frequency and therefore
suffers from less leakage than the moving average
filter.
You can force PicoScope to use one or other of the filter types by adjusting the
Samples control in the Capture Setup toolbar to make the ratio f
C
/f
S
fall into one of
the two ranges shown in the table. As the table shows, the cut-off frequency must be
below half the sampling frequency.