Computer-Based Calibration and Measurement of an EEG Data Acquisition System

A two-part procedure is described for computer-based calibration and measurement of an EEG data acquisition system. The main innovation lies in the application of trains of computer-generated (sin t)/t time-domain "impulses" with theoretically known and nearly ideal spectral characteristics, to measure and periodically verify the complete in-band frequency and phase response of the system. If and only if homogeneity of channel response has been demonstrated to hold at all frequencies over channels and occasions, routine calibration of the system for each recording session can be effectively and quickly accomplished by equating system response under computer control at a single frequency, for example, through the use of a simple sine wave calibration signal. Thus, a strong technical foundation is provided for assuring instrumental reliability and validity in electrophysiological measurements. Illustrative results of the system-measurement procedure are presented, and mathematical and computational details are supplied in a technical Appendix.