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. Author manuscript; available in PMC: 2010 Feb 18.
Published in final edited form as: Curr Protoc Neurosci. 2009 Oct;CHAPTER:Unit10.2. doi: 10.1002/0471142301.ns1002s49

Figure 4.

Figure 4

Frequency-response curve for the hardware low frequency and high frequency filters on the Grass-Telefactor H2O ambulatory EEG recorder. Output amplitude as a percent of input amplitude is plotted against frequency (on a logarithmic scale). Signals between 2 and 13 Hz are largely unaffected (<2% decrease) by the filters. The low-frequency filter is a 0.3 Hz ½ amplitude filter with a 6-dB per octave roll off. A 0.5-Hz signal is decreased by ~30%; a 0.3-Hz signal is decreased by ~50 %. The high frequency filter decreases a 50 Hz signal by ~20% and a 100Hz signal by ~60%.