A New Technique for Monitoring Heart Signals-Part I: Instrumentation Design

A new noninvasive method for obtaining the human electrocardiogram is investigated in this paper. The proposed technique uses a composite conductive medium formed by the patient´s body and the external liquid medium such as tap water in a bathtub. In this Part I of a two part paper, the emphasis is on the instrumentation design. An in-depth study of the frequency characteristics of the liquid medium interface with the sensing electrodes and the electronic instrumentation system is also presented. Filtering and amplifying circuitry is designed to obtain ECG signals from the noisy bathtub signals. This improves the signal-to-noise ratio from approximately -20 to about 40 dB while amplifying the signal level from 0.1 mV to 1 V. In Part II, signal processing techniques are developed to extract the standard orthogonal leads from the bathtub signals.