AVERAGING METHOD FOR PERIODIC STRAYS ELIMINATION AND THE TIMING CIRCUIT FOR EVOKED RESPONSES MEASURING SET-UP FOR APPLYING THE METHOD

摘要

An averaging method which eliminates periodic strays and which is used in analog-digital computers performing an averaging procedure. Such a procedure which processes a set of signals picked up from an examined object elicits an averaged evoked response due to its capability of reducing internal noise and periodic strays originated in an environment comprising a mains supply network proportionally to the square root of N-sweeps of the procedure, and in the case where the periodic strays and external stimuli are synchronous, the averaged periodic strays are not sufficiently reduced and distort the averaged evoked response making its right interpretation difficult. In order to overcome this problem, the averaging method eliminates the periodic strays from the set of signals during the averaging procedure in greater extend i.e. proportionally to the number of N-sweeps of the averaging procedure resulting in their at least N-fold reduction thanks to introducing a phase shift by an angle .alpha. of the 120.degree. ? .alpha. ?240.degree. interval related to the period of the strays which controls periods of the external stimuli and initial phases of the periodic strays at the beginning of two successive periods of the external stimuli, or alternately at the beginning of two sucessive sweeps of the averaging procedure differing by the value of the introduced phase shift, i.e. by .alpha..