The single channel ECG machine contains one amplifier channel and one recording system. Such machines usually have a multi positioning switch, by selecting the switch the desired lead connection can be selected. Only one lead at a time can be recorded or printed with such type of ECG Machine .
The Multichannel ECG ( 3/6/12 channel ) consists several amplifier channels and a corresponding number of recording systems . This facilitates recording of several ECG leads simultaneously and thus considerably reduces the time required to complete a set of recordings.
In Modern 3/6/12 ECG machines use microprocessor to capture the heart signals from standard 12 leads configuration, sequencing the lead selector to capture four groups of 3 lead signals and switching groups every few seconds.
In 3 channels machines the ECG signals selected by the microprocessor are amplified , filtered and sent to a 3 channel multiplexer. The multiplexed analog signals are then given to an analog to digital converter which is then stored and sent to digital to analog converter for reconstructing the analog signals and these signals are de-multiplexed and passed to the chart recorder / Printer or video display to display the same .
3 channel ECG Machine prints 3 waveforms at a time on the charting paper ( Waveform I,II,II )
3 waveform in 2nd slot ( aVR , aVL, aVF )
3 waveform in 3rd slot ( V1, V2, V3 )
3 waveform in 4th slot ( V4, V5,V6 )
To print all the 12 waveform it takes 4 slot on the ECG chart paper ( It is also called 3x4 format ) . below fig shows a ECG report from 3 channel ECG Machine . Print report from 3 ch ECG machine is usually longer on paper as compare to 6 channel and 12 channel ECG Machine .
3 channel ECG report are usually printed on 60mm/80mm or 100mm ECG paper depending on the size of printer available in the machine .
Similarly in 6 channels and 12 channels there are 6 channels and 12 channels multiplexer in the machine. In 6 channel ECG Machine 6 waveforms are printed simultaneously . So 12 waveforms can be printed in just 2 slots of the paper ( Its format is called 6x2 format )
In 12 channel ECG machine all 12 channel of the ECG are printed in one slot ( so its format is called 1x12 format )
below fig shows a print report of 12 channel ECG Machine . 12 channel ECG report are attractive in look because all waveforms can be compare simultaneously .
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