Noise Analysis > Signal Conditioning
The analogue signal conditioning requirements for signals intended for noise analysis are somewhat stricter than for other applications A low-pass anti-aliasing filter with sharp cut-off characteristics (Butterworth or Chebyshev) is essential. (Suitable filters include the Frequency Devices 901 or Kemo VBF-8) The cut-off frequency of this filter should be set to slightly less than half of the digital sampling rate.
In some studies, e.g. endplate noise at the neuromuscular junction, the current fluctuations are a small fraction of the mean current. In these circumstances, it may be necessary to use a high-pass filter to separate out the noise from the mean current signal, amplify by X10-X100, and digitise it on a second input channel (See Dempster 2001).