4-3
4.5
Filter
Analog filtering is used during data acquisition to lower the output noise. The analog
filtering in the BAS 100B/W is a two stage network (Figure 4-4). The first stage is an
RC filter, which is followed by a Bessel filter. The filtering characteristics of each
stage can be varied, and are related to the time scale of the technique being used. The
capacitor in the RC filter should be chosed to give a time constant (RC) that is at least
10 times smaller than the time scale of the experiment. Similarly, the cut-off
frequency for the Bessel filter must be at least 10 times larger than the frequency of
the electrochemical technique being used. If too much filtering is used, then
significant distortion of the experimental data can occur.
Figure 4-4. Filter dialog box.
The amount of filtering used can be determined automatically using the Auto option
(this is the default option). It is generally advisable to use this option. However, the
filters can be changed by the user through the Manual option (the desired filter is
selected fromdrop-down list boxes).
When the Low Current Module (LCM) is being used, the BAS 100B/W filters are
disabled by the Auto option, and the only the LCM Filter is used. The BAS 100B/W
filters can be re-enabled using the Manual option.
