165-072011 THCD-100 Power Supply Page 10 of 28
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 off the filtering, irrespective of the band setting.
It should be noted that 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 preset 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 slugged (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.