Technik in der Kardiologie

Abstract

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An ECG simulator with a novel ECG profile for physiological signals

“…The P-wave corresponds to the depolarisation of the atria, while the QRS-complex represents the superposition of the signals generated during the repolarisation of the atria and the depolarisation of the ventricles. Subsequently, the T-wave arises because of ventricular repolarisation (although investigated for a while, the origin and clinical importance of the U-wave, which follows the Twave, is still not fully understood [3] and thus not considered in this work) [9].…”

“…The filter of this device is implemented as an RC-network with a cutoff-frequency of 20 Hz. As ECG signals contain relevant frequencies between 0.05 Hz and 200 Hz [9] an adaptation of the output-circuit is required. Thus, the capacitors of the RC-circuits are bypassed with 100 X resistors (the online supplement contains detailed instructions on what components to change).…”

“…The sound card generates output signals with 2 V pp using 16 Bits which corresponds to a resolution of 0.03 mV/Bit. This is too low for both ECG signals with R-peaks of 1 mV and for common-mode signals in the range of 10 V [9]. As the output range of the card further depends on the volume setting of the computer, the custom-made circuit in Figure 8 is developed translating sound card output to real-world signal intensities (to start with calibration of the system followed by attenuation/amplification of the output signals).…”

“…The associated circuit attenuates the signal by a divisor of 1000 to obtain typical ECG signal intensities with high resolution. The third switch position is used to amplify a 50 Hz common mode signal simulating capacitive coupling of the human body with surrounding power lines [9]. Signal-amplification to 10 V pp is achieved by a non-inverting amplifier with a gain of 10.…”