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A spherical polarcardiograph computer Poole, Edward Graham

Abstract

Until recently, the major portion of the study of the electrical activity of the heart has been done with the aid of electrocardiograms and vectorcardiograms. However, such information as the variation of the magnitude and angle of the heart vector with time is not directly discernible from either of these recordings. A polarcardiograph was developed by W.K.R. Park to present the plane projection of the heart vector in magnitude and angle as a continuous function of time. The polarcardiograph proved to be useful but it was not sufficiently stable. An electronic device which would be stable and at the same-time present the heart vector in three dimensions, magnitude, frontal angle and polar angle as continuous functions of time, would be useful in electrocardiographic research. The design of such a computer, the "spherical polarcardiograph", is described in this thesis. The spherical polarcardiograph, which must compute the spherical polar coordinates of points from their respective Cartesian coordinates, has been developed using analog multipliers, subtracters and adders as well as a two-phase sinusoidal voltage source and a device for generating a voltage proportional to the phase difference of two sinusoidal signals. With the exception of the third coordinate computation and the gated feedback circuitry, the system is similar to that used by Park. Automatic balancing of the circuit occurs for a short interval during the rest period of the heart. The spherical polarcardiograph has not been constructed in final form but tests on the individual units indicate that the instrument will be well within the accuracy required for normal electrocardiographic purposes.

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