Estimation of the required bandwidth of a DC amplifier for measurement of eye saccades
Röske, W.
Eeg-Emg Zeitschrift für Elektroenzephalographie Elektromyographie und verwandte Gebiete 19(2): 106-107
1988
ISSN/ISBN: 0012-7590 PMID: 3135994 Document Number: 307594
Saccadic eye movements are analysed with DC-amplifiers when electrodes are used. The present investigation on measuring the velocity of eye movement gives an estimation for the required bandwidth, because the upper frequency has a decisive influence on the result. Theoretically there would be no error of measurement if no filters were used. But there are two reasons for filtering. One is that the Shannon-Theorem asks for a limited frequency in order to digitize the signal on a computer later on. The other is an increasing of disturbance in the signal by an extended top frequency. It takes no trouble to solve the first problem by changing the sampling-rate of the computer. The second problem asks for a compromise. Error in measurement will increase by reducing the top frequency, but also disturbances in the signal will be reduced. The value in question of this investigation is the velocity of eye movement, i.e. the maximum gradient in the signal and that could be the gradient of a disturbance-spike. The present estimation shows that an amplifier with two RC-Filters and a Butterworth-Filter second order with a resulting top frequency at 20 Hz (3 dB-limit) offers a good compromise.