THCD-401 Instruction Manual
Page 40 of 47
(a)
Operational band
The filter can be configured to only operate within a certain band, meaning that excursions between
subsequent readings that fall outside that band are shown as real (and not filtered) readings. The band is
configurable between 0.01% and 1.00% of the full-scale range of the channels. It can also be set to OFF, which
means that no filtering is performed (i.e. every reading is a ‘real’ one) and can also be set to ON which means
that filtering is always shown no matter how big of an excursion occurs.
(b)
Filter size
The size of the filter is currently configurable between 0 and 6 seconds and simply indicates the amount of
readings that are taken and buffered to calculate and show the averaged reading. A filter size of 0 will
naturally turn the filtering off, irrespective of the band setting.
NOTE: this type of adaptive filtering can cause readings to be displayed abnormally, particularly if the
buffer size is one of the larger available settings, where the displayed readings seem to ‘jump about’ as
the filter is disabled and then re-enabled when the data excursions fall into the pre-set band. This is because
outside of the band, the display will show the ‘real’ unfiltered readings (whilst constantly taking an average in
the background). When the excursions fall into the band then the display will switch to showing the filtered
data. If this data is quite significantly slowed (due to a large buffer size) then the display will appear to nearly
reach the new data value (due to ‘real’ values being shown) and then jump back to the filtered data which
could be several seconds behind. Because of this, the setting of a buffer size greater than 5 seconds will
automatically change the band to ON, meaning that filtered data will always be shown.
Selecting different filter band/size combinations will reduce these anomalies, turning the band OFF and ON
will stop this anomaly.
