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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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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
Protection circuit Lead selector Calibration signal Preamplifier Isolation circuit Driven right leg system Driver amplifier Memory System Microcomputer Recorder - Printer ECG Functional Blocks
The Electrocardiogram • Outline • The ECG • Specific Requirements • Functional Blocks • Frequent Problems • Some Solutions
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
Electrostatic Shield - to eliminate electric-field interference