Thesis

An apparatus for processing of electrophysiological signals

An apparatus for processing of electrophysiological signals has been designed and built. It has advantages over similar existing devices in that it is frequency independent over the range of electrophysiological signals, is simple to use, and inexpensive. The instrument is versatile, since it is capable of threshold detection, amplitude discrimination, frequency and interval analysis, and also determination if the frequency or interval of the examined signal falls within, above, or below a predetermined band. The design is based on the method of threshold detection of analog signals. Incoming signals are detected in a voltage window comparator with two adjustable threshold levels and converted into digital pulses. Further signal processing is then performed digitally by CMOS logic circuitry. The outputs of the apparatus are available in a form of an analog voltage for interfacing with analog devices and pen writing instruments and also in the form of a 12 bit digital word for interfacing with digital equipment and computers for further data processing. A digital readout display is also provided. The design is modular and each of the building blocks can be used separately to perform a specific task. As a demonstration of the feasibility of the instrument for actual physiological data processing, preliminary data on heart rates during and after exercise and on pacemaker firing rates in cardiac patients are compiled here, and examples for further use in electrophysiology and medicine are suggested.

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