The QT interval is the time from the beginning of the QRS complex, representing ventricular depolarization, to the end of the T wave, resulting from ventricular repolarization. The normal QT interval is controversial, and multiple normal durations have been reported.

Typically, the amplitude value is in the 0.5 mV to 1 mV range for heart rate between 60 beats per minute and 100 beats per minute. Hence a designer normally uses an amplifier to strengthen the signal, set an offset to the scope channel, and even use waveform averaging to capture an accurate ECG signal.

The standard ECG is by convention limited to 0.05-150 Hz, but higher frequencies are also present in the ECG signal [Golden et al., 1973]. With high-resolution technology, it is possible to record and analyze these higher frequencies.

Another quick way to calculate the rate is based on the entire ECG being 10 seconds. By counting the number of QRS complexes and multiplying by six, the number per minute can be calculated — because 10 seconds times six equals 60 seconds, or 1 minute.

On the signal filtering section, frequency of interest for each ECG, EMG and EEG is different. ECG filtering frequency is in the range of 0. 05Hz to 150Hz, EMG is in the range of 20-2000Hz and EEG is 13-30Hz (beta frequency only).

[13] found that a QRS complex ranges in sampling frequencies between 10 Hz and 25 Hz. This means that the sampling frequency should be at least 50Hz. Real implementations of ECG recorders include sampling frequencies of more than 100 Hz, up to 500 Hz, or in lab environments up to 1000 Hz.

The electroencephalogram (EEG) is the depiction of the electrical activity occurring at the surface of the brain. Frequency (Hertz, Hz) is a key characteristic used to define normal or abnormal EEG rhythms. Most waves of 8 Hz and higher frequencies are normal findings in the EEG of an awake adult.

However, the most frequently used method to classify EEG waveforms is by the frequency, so much so, that EEG waves are named based on their frequency range using Greek numerals. The most commonly studied waveforms include delta (0.5 to 4Hz); theta (4 to 7Hz); alpha (8 to 12Hz); sigma (12 to 16Hz) and beta (13 to 30Hz).

Differences in the speed of wavefront propagation through the cardiac cycle are reflected by different frequencies content of ECG waves. The content of T wave lays mostly within a range from zero (DC) to 10 Hz. The content of P wave is characterized by 5-30 Hz frequencies.

Waveform Description. (Normal ECG is shown below – Compare its waveforms to the descriptions below) It is important to remember that the P wave represents the sequential activation of the right and left atria, and it is common to see notched or biphasic P waves of right and left atrial activation.

Electrocardiogram Sampling Frequency Range Acceptable for Heart Rate Variability Analysis A 250-Hz sampling frequency would be acceptable for HRV analysis. When frequency-domain analysis is not required, a 100-Hz sampling frequency would also be acceptable. A 250-Hz sampling frequency would be acceptable for HRV analysis.

ST Segment and T wave. The normal T wave is usually in the same direction as the QRS except in the right precordial leads. In the normal ECG the T wave is always upright in leads I, II, V3-6, and always inverted in lead aVR. Normal ST segment elevation: this occurs in leads with large S waves (e.g., V1-3),…