Transcript The Electrocardiogram

ECG Signal Make-up
1
Biopotential Requirements
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High Input Impedance
– Minimum loading of the signal being measured
– Minimum 10MW
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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
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ECG Functional Blocks
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8.
Protection circuit
Lead selector
Calibration signal
Preamplifier
Isolation circuit
Driven right leg
system
Driver amplifier
Memory System
9.
10.
Microcomputer
Recorder - Printer
3
The Electrocardiogram
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Outline
The ECG
Specific Requirements
Functional Blocks
Frequent Problems
Some Solutions
4
Heart Dipole
5
Cardiac Vector
6
Eindhoven’s Triangle
7
Wilson’s Central Terminal
Connection
8
Augmented Leads
9
Comparing Augmented leads to
Standard Leads
10
Precordial Leads
11
Problems Frequently
Encountered
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Frequency Distortion
Saturation or Cutoff Distortion
Ground Loops
Open Lead Wires
Artifacts from Large Electric Devices
Interference From Electric Devices
Electromagnetic Interference
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Frequency Distortion
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Saturation - cutoff Distortion
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Ground Loops
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Ground Loops - 2
16
Artifacts from large electric
devices
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(a) 60 Hz Line Interference
(b) EMG interference
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Mechanism of electric-field
pickup from Power line
19
Current flows from the power
line into the body
20
Magnetic-field Pickup by ECG
21
Voltage protection scheme at
input
22
Voltage limiting device
23
Electrostatic Shield - to eliminate
electric-field interference
24
Driven-Right-Leg System
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Equivalent Ct. of a driven right
leg system
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Bio-Signals Charachteristics
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ECG Amplifier
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