Spacelabs Healthcare elance 5, Service Manual

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Theory
ECG Block Diagram
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ECG detection is by means of measuring the voltage of the QRS signal from the heart muscle.
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Patient ECG is acquired via ECG lead wires.
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Individual ECG lead signal is fed through a multiplexer for processing.
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ECG signal from the multiplexer is fed to pacer detector to identify pacer spike for elimination
subsequently. It is also sense for leadoff condition by leadoff detector.
- ECG signal is amplified by amplifiers.
- Amplified ECG signal is then sent to the analog to digital converter for conversion.
- Digitized ECG signal is sent to the microcontroller for processing.
Respiration Block Diagram
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Patient respiration detection is by means of impedance pneumography.
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RESP signal is acquired via RA and LL of ECG lead wires.
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Thoracic impedance is detected by passing a 28 kHz carrier to electrodes RA and LL.
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Leadoff detection circuitry is used to detect lead off conditions.
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The acquired signal is fed through a demodulator to recover the outline of the respiration pattern.
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The signal is sent to A/D for digital conversion.
- Digitized signal is sent to microcontroller for processing.
3-2
MUX
AMP A/D
Converter
PACER /
LEADOFF
Detection
ECG
Input
MUX
DEMOD
A/D
Converter
LL
RA
LEAD OFF
Detection
28 KHz
RESP
Input