This paper describes the development of a very low-power preamplifier intended for use in pasteless-electrode recording of the human electrocardiogram. The expected input signal range is 100 microV-10 mV from a lead-II electrode configuration. The amplifier provides a gain of 43 dB in a 3-dB bandwidth of 0.05 Hz-2 kHz with a defined high input impedance of 75 M omega. It uses a driven common electrode to enhance rejection of common-mode interfering signals, including low-frequency motion artifact, achieving a common-mode rejection ratio (CMRR) of better than 80 dB over its entire bandwidth. The gain and phase characteristics meet the recommendations of the American Heart Association, ensuring low distortion of the output ECG signal and making it suitable for clinical monitoring. The amplifier has a power consumption of 30 microW operating from a 3.3-V battery and is intended for use in small, lightweight, portable electrocardiographic equipment and heart-rate monitoring instrumentation.

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This paper reports the measurement of the properties of dry or pasteless conductive electrodes to be used for long-term recording of the human electrocardiogram (ECG). Knowledge of these properties is essential for the correct design of the input stage of associated recording amplifiers. Measurements were made on three commercially available conductive carbon based electrodes at pressures of 5 mmHg and 20 mmHg, located on the lower abdomen of the body on three subjects having different skin types. Parameter values were fitted to a two-time-constant based model of the electrode using data measured over a period of 10s. Values of resistance, ranging from 40kOmega to 1590kOmega and of capacitance ranging from 0.05 microF to 38 microF were obtained for the components, while the values of the time-constants varied from 0.07 s to 3.9s.

This article reports the design and development of an ECG simulator intended for use in the testing, calibration and maintenance of electrocardiographic equipment. It generates a lead II signal having a profile that varies with heart rate in a manner which reflects the true in vivo variation. Facilities are provided for user adjustment of heart rate, signal amplitude, QRS complex up-slope, and the relative amplitudes of the P-wave and T-wave. The heart rate can be set within the range 30-200 beats min(-1) in steps of 1 beat min(-1). The amplitude of the QR5 complex can be adjusted from 0.1-20 mV in 0.1 mV steps, while its up-slope can be set between 10 and 50 ms with a 1 ms resolution. The amplitude of the P-wave can be varied from 5-40% and that of the T-wave from 10-80% of the amplitude of the QRS complex with a 1% resolution.

Pattern recognition, and in particular dynamic time warping has been applied to the ECG for many different purposes over the last decade. Significant research on creating adaptive, feature based, and more complex forms of the algorithm in order to increase its ability to classify an ECG signal accurately has been performed. Despite this increase in complexity and in the number of variations of the dynamic time warping algorithm there has been less focus on actually using the results of dynamic time warping to relate the reference and test signals to each other as accurately as possible. The majority of dynamic time warping algorithms published in the literature, even the most complex of them, classify the most accurate match to a reference signal based only on resulting Euclidean distance or slope difference between samples of the known reference and unknown query signal. This article demonstrates how a combination of measurements including heart-rate, amplitude and required warping time alignment can be used to reduce the resulting error in the classification of a query signal after the query and reference signals have been warped together. Its benefits are verified with significant testing.