Fukuda Denshi DS-7001, Service Manual

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Circuit Explanation of the Analog Board
ECG Measurement Circuit
ECG relay cable and ECG lead cable are connected to the ECG input connector, and ECG
signals are input to the ECG measurement circuit. At the ECG measurement circuit, signal
amplification, filtering is performed, and converted to digital signal. Then, the signals are
isolated and transmitted to the CPU. At the CPU, ECG signals are filtered, and HR
measurement is performed.
Filtering, QRS detection, lead-off detection, HR measurement are all performed by the software.
Respiration Measurement Circuit
The respiration measurement is performed by impedance method which detects the thoracic
movement by measuring the thoracic impedance from the ECG electrodes.
A weak current of high-frequency is delivered between the ECG electrodes, and impedance
change is detected by measuring the potential difference between the electrodes using the
synchronous rectification method. After signal amplification and filtering, the signals are A/D
converted, isolated, and transmitted to the CPU. At the CPU, the respiration signals are filtered
and respiration measurement is performed.
Control Part
Communicates with the CPU board, and controls each measurement operation.
MPX (Multiplexer), A/D Converter
Analog signal is selected by the multiplexer, and 12bit A/D conversion is performed.
The A/D conversion and multiplexer are controlled by the CPU board.
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