Waters ACQUITY UPLC Operator's, Overview And Maintenance Manual page 27

Filtering noise
The detector uses a Hamming filter to minimize noise. The Hamming filter is
a digital finite-impulse-response filter that creates peak-height degradation
and enhances the filtering of high frequency noise.
The behavior of the filter depends on the filtering-time constant, or
"filter-time" constant, that you select. You can program a filtering time to be
Fast, Slow, Normal, or Other. If you select Fast, Slow, or Normal, you need not
enter a value. The filtering constant is determined by the data rate. If you
select Other, you can enter a value. Nevertheless, the value you enter is
rounded up or down to a value based on the data rate.
The filter-time constant adjusts the filter response time to achieve an optimal
signal-to-noise ratio. Selecting Other and entering a value of 0.0 disables all
filtering.
Lower filter-time constant settings produce these effects:
• Narrow peaks with minimal peak distortion and time delay
• Very small peaks become more difficult to discriminate from baseline
noise
• Less baseline noise is removed
Higher filter-time constant settings produce these effects:
• Greatly decrease baseline noise
• Shorten and broaden peaks
The software includes fast or normal filter-time constants at each data rate
that are appropriate for high speed or high sensitivity applications,
respectively.
The following figure shows the relationship between increased filter-time
constant and absorbance.
Operating principles of the light-guiding flow cell 15