Before we can discuss the use of these types filters with an ADInstruments Powerlab , it is import to understand what aliasing actually is. According to the Nyquist theorem, in order to resolve a signal component correctly, the sampling rate needs to be at least twice the signal frequency (i.e. to resolve a 50 Hz signal component, the sampling rate should be at least 100 samples per second [100 Hz]).
However, using this example, signal components higher than 50 Hz will appear as a lower frequency than they actually are when sampled at 100 Hz. This phenomenon is known as signal aliasing.
An anti-aliasing filter looks at the user-specified sampling frequency and removes any under-sampled frequencies that may appear in the signal (i.e. signal component frequencies >0.5 of the sampling frequency).
Current PowerLab models with Anti-Aliasing filter include the PowerLab 15T, 26T, 2/26, and 4/26.
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