How to measure ECG by ECG monitor

Electrocardiogram (ECG) is an electrocardiograph (ECG) monitor that records the changes of cardiac potential from the surface of the body. It reflects the changes of biopotential in the process of excitation, conduction and recovery. The ECG consists of a P wave, a QRS wave group, a T wave and a U wave. As shown in the following figure, arrhythmia and other events can be analyzed by waveform extraction. The amplitude of ECG is generally between 5 and 5 mV, and the frequency range is 0.05-100 Hz. The heart rate (HR) can be calculated from the R-R interval.

The ECG monitor measures the potential difference between the two electrodes. The monitor manufacturer obtains it through the lead. The specific electrode position is shown in the following figure.EEG machine

Initially defined I, II, III leads are called bipolar standard limb leads, and then defined compression unipolar limb leads aVR, aVF, aVF and V1, V2, V3, V4, V5, V6. These leads are currently used in clinical standard ECG leads. Because the heart is three-dimensional, a waveform of leads represents electrical activity on a projection plane of the heart. These 12 leads will reflect electrical activity on different projection planes of the heart from 12 directions, thus comprehensive diagnosis of different parts of the disease. At present, the standard electrocardiograph used in clinical measurement of ECG, its limb electrodes are placed in the wrist and ankle, and as the electrodes in ECG monitoring is placed in the chest and abdomen region of patients, clinical commonly used lead for standard limb lead and unipolar chest lead V, a total of five electrodes. Although the positions are different, they are equivalent, so the ECG leads in the ECG monitor correspond to those in the ECG monitor, they have the same polarity and waveform.

ECG measurement circuit realizes the detection and amplification of ECG signals, and digitized ECG signals are obtained by A / D conversion. Then the waveform detection and heart rate value are calculated by software. The measuring principle is shown in the following figure.EEG machine

The monitor manufacturer uses the right leg drive method to eliminate the common touch interference introduced by the human body. The selected ECG is amplified by a preamplifier composed of a high-precision operational amplifier, coupled to the latter stage, filtered by a band-pass filter, and then converted to the main controller by A/D.EEG machine