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ECG Signal Make-up

ECG Signal Make-up. Biopotential Requirements. High Input Impedance Minimum loading of the signal being measured Minimum 10M W Input circuit must have isolation and protection circuits to protect the patient Output Impedance must be low compared to the load impedance

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ECG Signal Make-up

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  1. ECG Signal Make-up

  2. Biopotential Requirements • High Input Impedance • Minimum loading of the signal being measured • Minimum 10MW • Input circuit must have isolation and protection circuits to protect the patient • Output Impedance must be low compared to the load impedance • Proper bandwidth range. Not too narrow and not too wide • Gain at least 1000 times • For bipolar electrodes, use differential amplifier

  3. Protection circuit Lead selector Calibration signal Preamplifier Isolation circuit Driven right leg system Driver amplifier Memory System Microcomputer Recorder - Printer ECG Functional Blocks

  4. The Electrocardiogram • Outline • The ECG • Specific Requirements • Functional Blocks • Frequent Problems • Some Solutions

  5. Heart Dipole

  6. Cardiac Vector

  7. Eindhoven’s Triangle

  8. Wilson’s Central Terminal Connection

  9. Augmented Leads

  10. Comparing Augmented leads to Standard Leads

  11. Precordial Leads

  12. Problems Frequently Encountered • Frequency Distortion • Saturation or Cutoff Distortion • Ground Loops • Open Lead Wires • Artifacts from Large Electric Devices • Interference From Electric Devices • Electromagnetic Interference

  13. Frequency Distortion

  14. Saturation - cutoff Distortion

  15. Ground Loops

  16. Ground Loops - 2

  17. Artifacts from large electric devices

  18. (a) 60 Hz Line Interference(b) EMG interference

  19. Mechanism of electric-field pickup from Power line

  20. Current flows from the power line into the body

  21. Magnetic-field Pickup by ECG

  22. Voltage protection scheme at input

  23. Voltage limiting device

  24. Electrostatic Shield - to eliminate electric-field interference

  25. Driven-Right-Leg System

  26. Equivalent Ct. of a driven right leg system

  27. Bio-Signals Charachteristics

  28. ECG Amplifier

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