Averaging method for periodic strays elimination and a counting circuit for evoked responses measuring set-up for applying the method

Claim 1

An averaging method for elimination of periodic strays in averaging devices and computers employing an averaging procedure in electrophysiological analysis of a subject, the method comprising the steps of: stimulating the subject through the use of stimulation means; sensing a set of signals from the subject by means of electrodes, the set of signals consisting of internal noise and individual evoked responses of an examined subject as well as periodic strays induced in the subject from an environment; amplifying the set of signals with an instrumentation amplifier; transmitting the set of signals to an averager; eliminating the internal noise through the use of an averaging procedure in an averager; said averaging procedure using a number N of stimuli repetitions to reduce the internal noise through reinforcement of the periodic evoked response signal while achieving at least a square root of N signal-to-noise ratio reduction through non-reinforcement of the random internal noise; sensing a periodic stray signal with frequency 1/t from the environment with a sensing circuit; supplying the periodic stray signal to a half-period detecting circuit; determining the half-period of the periodic stray signal in the detecting circuit; generating half-period pulses of frequency 2/t in the detecting circuit; transmitting the half-period pulses to a counting circuit; counting the half-period pulses in the counting circuit; determining a triggering frequency 1/T in a programming circuit, T being equal to the half-period multiplied by an odd natural number which is chosen to allow a period as close as possible to a selected length; transmitting the pulses of frequency 1/T to a triggering circuit; initiating the averaging procedure with frequency 1/T in a triggering circuit; sending simultaneous initiation signals from the triggering circuit to the averager and to the stimulation means; the method resulting in the reduction of periodic stray signals in proportion to the number of stimulus repetitions, N.